GCC 1 2006-05-06 gcc-4.1.1 GNU
NAME
gcc - GNU project C and C++ compiler
SYNOPSIS
gcc [--cc|--SS|--EE] [--ssttdd==_s_t_a_n_d_a_r_d]
[--gg] [--ppgg] [--OO_l_e_v_e_l]
[--WW_w_a_r_n...] [--ppeeddaannttiicc]
[--II_d_i_r...] [--LL_d_i_r...]
[--DD_m_a_c_r_o[=_d_e_f_n]...] [--UU_m_a_c_r_o]
[--ff_o_p_t_i_o_n...] [--mm_m_a_c_h_i_n_e_-_o_p_t_i_o_n...]
[--oo _o_u_t_f_i_l_e] _i_n_f_i_l_e...
Only the most useful options are listed here; see below for the
remainder. gg++++ accepts mostly the same options as ggcccc.
DESCRIPTION
When you invoke GCC, it normally does preprocessing, compilation,
assembly and linking. The "overall options" allow you to stop this
process at an intermediate stage. For example, the --cc option
says not to run the linker. Then the output consists of object files
output by the assembler.
Other options are passed on to one stage of processing. Some options
control the preprocessor and others the compiler itself. Yet other
options control the assembler and linker; most of these are not
documented here, since you rarely need to use any of them.
Most of the command line options that you can use with GCC are useful
for C programs; when an option is only useful with another language
(usually C++), the explanation says so explicitly. If the description
for a particular option does not mention a source language, you can use
that option with all supported languages.
The ggcccc program accepts options and file names as operands. Many
options have multi-letter names; therefore multiple single-letter options
may _n_o_t be grouped: --ddrr is very different from --dd --rr.
You can mix options and other arguments. For the most part, the order
you use doesn't matter. Order does matter when you use several options
of the same kind; for example, if you specify --LL more than once,
the directories are searched in the order specified.
Many options have long names starting with --ff or with
--WW---for example,
--ffssttrreennggtthh--rreedduuccee, --WWffoorrmmaatt and so on. Most of
these have both positive and negative forms; the negative form of
--ffffoooo would be --ffnnoo--ffoooo. This manual documents
only one of these two forms, whichever one is not the default.
OPTIONS
OOppttiioonn SSuummmmaarryy
Here is a summary of all the options, grouped by type. Explanations are
in the following sections.
-
_O_v_e_r_a_l_l _O_p_t_i_o_n_s
--cc --SS --EE --oo _f_i_l_e --ccoommbbiinnee --ppiippee --ppaassss--eexxiitt--ccooddeess
<>
--xx _l_a_n_g_u_a_g_e --vv --###### ----hheellpp ----ttaarrggeett--hheellpp ----vveerrssiioonn
-
_C _L_a_n_g_u_a_g_e _O_p_t_i_o_n_s
--aannssii --ssttdd==_s_t_a_n_d_a_r_d --aauuxx--iinnffoo _f_i_l_e_n_a_m_e
-
--ffnnoo--aassmm --ffnnoo--bbuuiillttiinn --ffnnoo--bbuuiillttiinn--_f_u_n_c_t_i_o_n
--ffhhoosstteedd --ffffrreeeessttaannddiinngg --ffmmss--eexxtteennssiioonnss
--ttrriiggrraapphhss --nnoo--iinntteeggrraatteedd--ccpppp --ttrraaddiittiioonnaall --ttrraaddiittiioonnaall--ccpppp
--ffaallllooww--ssiinnggllee--pprreecciissiioonn --ffccoonndd--mmiissmmaattcchh
--ffssiiggnneedd--bbiittffiieellddss --ffssiiggnneedd--cchhaarr
--ffuunnssiiggnneedd--bbiittffiieellddss --ffuunnssiiggnneedd--cchhaarr
-
_C_+_+ _L_a_n_g_u_a_g_e _O_p_t_i_o_n_s
--ffaabbii--vveerrssiioonn==_n --ffnnoo--aacccceessss--ccoonnttrrooll --ffcchheecckk--nneeww
<>
--ffccoonnsseerrvvee--ssppaaccee --ffffrriieenndd--iinnjjeeccttiioonn --ffnnoo--ccoonnsstt--ssttrriinnggss
--ffnnoo--eelliiddee--ccoonnssttrruuccttoorrss
--ffnnoo--eennffoorrccee--eehh--ssppeeccss
--ffffoorr--ssccooppee --ffnnoo--ffoorr--ssccooppee --ffnnoo--ggnnuu--kkeeyywwoorrddss
--ffnnoo--iimmpplliicciitt--tteemmppllaatteess
--ffnnoo--iimmpplliicciitt--iinnlliinnee--tteemmppllaatteess
--ffnnoo--iimmpplleemmeenntt--iinnlliinneess --ffmmss--eexxtteennssiioonnss
--ffnnoo--nnoonnaannssii--bbuuiillttiinnss --ffnnoo--ooppeerraattoorr--nnaammeess
--ffnnoo--ooppttiioonnaall--ddiiaaggss --ffppeerrmmiissssiivvee
--ffrreeppoo --ffnnoo--rrttttii --ffssttaattss --fftteemmppllaattee--ddeepptthh--_n
--ffnnoo--tthhrreeaaddssaaffee--ssttaattiiccss --ffuussee--ccxxaa--aatteexxiitt --ffnnoo--wweeaakk --nnoossttddiinncc++++
--ffnnoo--ddeeffaauulltt--iinnlliinnee --ffvviissiibbiilliittyy--iinnlliinneess--hhiiddddeenn
--WWaabbii --WWccttoorr--ddttoorr--pprriivvaaccyy
--WWnnoonn--vviirrttuuaall--ddttoorr --WWrreeoorrddeerr
--WWeeffffcc++++ --WWnnoo--ddeepprreeccaatteedd --WWssttrriicctt--nnuullll--sseennttiinneell
--WWnnoo--nnoonn--tteemmppllaattee--ffrriieenndd --WWoolldd--ssttyyllee--ccaasstt
--WWoovveerrllooaaddeedd--vviirrttuuaall --WWnnoo--ppmmff--ccoonnvveerrssiioonnss
--WWssiiggnn--pprroommoo
-
_O_b_j_e_c_t_i_v_e_-_C _a_n_d _O_b_j_e_c_t_i_v_e_-_C_+_+ _L_a_n_g_u_a_g_e _O_p_t_i_o_n_s
--ffccoonnssttaanntt--ssttrriinngg--ccllaassss==_c_l_a_s_s_-_n_a_m_e
-
--ffggnnuu--rruunnttiimmee --ffnneexxtt--rruunnttiimmee
--ffnnoo--nniill--rreecceeiivveerrss
--ffoobbjjcc--ccaallll--ccxxxx--ccddttoorrss
--ffoobbjjcc--ddiirreecctt--ddiissppaattcchh
--ffoobbjjcc--eexxcceeppttiioonnss
--ffoobbjjcc--ggcc
--ffrreeppllaaccee--oobbjjcc--ccllaasssseess
--ffzzeerroo--lliinnkk
--ggeenn--ddeeccllss
--WWaassssiiggnn--iinntteerrcceepptt
--WWnnoo--pprroottooccooll --WWsseelleeccttoorr
--WWssttrriicctt--sseelleeccttoorr--mmaattcchh
--WWuunnddeeccllaarreedd--sseelleeccttoorr
-
_L_a_n_g_u_a_g_e _I_n_d_e_p_e_n_d_e_n_t _O_p_t_i_o_n_s
--ffmmeessssaaggee--lleennggtthh==_n
-
--ffddiiaaggnnoossttiiccss--sshhooww--llooccaattiioonn==[oonnccee|eevveerryy--lliinnee]
-fdiagnostics-show-options
-
_W_a_r_n_i_n_g _O_p_t_i_o_n_s
--ffssyynnttaaxx--oonnllyy --ppeeddaannttiicc --ppeeddaannttiicc--eerrrroorrss
<>
--ww --WWeexxttrraa --WWaallll --WWaaggggrreeggaattee--rreettuurrnn --WWnnoo--aattttrriibbuutteess
--WWcc++++--ccoommppaatt --WWccaasstt--aalliiggnn --WWccaasstt--qquuaall --WWcchhaarr--ssuubbssccrriippttss --WWccoommmmeenntt
--WWccoonnvveerrssiioonn --WWnnoo--ddeepprreeccaatteedd--ddeeccllaarraattiioonnss
--WWddiissaabblleedd--ooppttiimmiizzaattiioonn --WWnnoo--ddiivv--bbyy--zzeerroo --WWnnoo--eennddiiff--llaabbeellss
--WWeerrrroorr --WWeerrrroorr--iimmpplliicciitt--ffuunnccttiioonn--ddeeccllaarraattiioonn
--WWffaattaall--eerrrroorrss --WWffllooaatt--eeqquuaall --WWffoorrmmaatt --WWffoorrmmaatt==22
--WWnnoo--ffoorrmmaatt--eexxttrraa--aarrggss --WWffoorrmmaatt--nnoonnlliitteerraall
--WWffoorrmmaatt--sseeccuurriittyy --WWffoorrmmaatt--yy22kk
--WWiimmpplliicciitt --WWiimmpplliicciitt--ffuunnccttiioonn--ddeeccllaarraattiioonn --WWiimmpplliicciitt--iinntt
--WWiimmppoorrtt --WWnnoo--iimmppoorrtt --WWiinniitt--sseellff --WWiinnlliinnee
--WWnnoo--iinntt--ttoo--ppooiinntteerr--ccaasstt
--WWnnoo--iinnvvaalliidd--ooffffsseettooff --WWiinnvvaalliidd--ppcchh
--WWllaarrggeerr--tthhaann--_l_e_n --WWuunnssaaffee--lloooopp--ooppttiimmiizzaattiioonnss --WWlloonngg--lloonngg
--WWmmaaiinn --WWmmiissssiinngg--bbrraacceess --WWmmiissssiinngg--ffiieelldd--iinniittiiaalliizzeerrss
--WWmmiissssiinngg--ffoorrmmaatt--aattttrriibbuuttee --WWmmiissssiinngg--iinncclluuddee--ddiirrss
--WWmmiissssiinngg--nnoorreettuurrnn
--WWnnoo--mmuullttiicchhaarr --WWnnoonnnnuullll --WWppaacckkeedd --WWppaaddddeedd
--WWppaarreenntthheesseess --WWppooiinntteerr--aarriitthh --WWnnoo--ppooiinntteerr--ttoo--iinntt--ccaasstt
--WWrreedduunnddaanntt--ddeeccllss
--WWrreettuurrnn--ttyyppee --WWsseeqquueennccee--ppooiinntt --WWsshhaaddooww
--WWssiiggnn--ccoommppaarree --WWssttaacckk--pprrootteeccttoorr
--WWssttrriicctt--aalliiaassiinngg --WWssttrriicctt--aalliiaassiinngg==22
--WWsswwiittcchh --WWsswwiittcchh--ddeeffaauulltt --WWsswwiittcchh--eennuumm
--WWssyysstteemm--hheeaaddeerrss --WWttrriiggrraapphhss --WWuunnddeeff --WWuunniinniittiiaalliizzeedd
--WWuunnkknnoowwnn--pprraaggmmaass --WWnnoo--pprraaggmmaass --WWuunnrreeaacchhaabbllee--ccooddee
--WWuunnuusseedd --WWuunnuusseedd--ffuunnccttiioonn --WWuunnuusseedd--llaabbeell --WWuunnuusseedd--ppaarraammeetteerr
--WWuunnuusseedd--vvaalluuee --WWuunnuusseedd--vvaarriiaabbllee --WWvvaarriiaaddiicc--mmaaccrrooss
--WWvvoollaattiillee--rreeggiisstteerr--vvaarr --WWwwrriittee--ssttrriinnggss
-
_C_-_o_n_l_y _W_a_r_n_i_n_g _O_p_t_i_o_n_s
--WWbbaadd--ffuunnccttiioonn--ccaasstt --WWmmiissssiinngg--ddeeccllaarraattiioonnss
<>
--WWmmiissssiinngg--pprroottoottyyppeess --WWnneesstteedd--eexxtteerrnnss --WWoolldd--ssttyyllee--ddeeffiinniittiioonn
--WWssttrriicctt--pprroottoottyyppeess --WWttrraaddiittiioonnaall
--WWddeeccllaarraattiioonn--aafftteerr--ssttaatteemmeenntt --WWppooiinntteerr--ssiiggnn
-
_D_e_b_u_g_g_i_n_g _O_p_t_i_o_n_s
--dd_l_e_t_t_e_r_s --dduummppssppeeccss --dduummppmmaacchhiinnee --dduummppvveerrssiioonn
<>
--ffdduummpp--uunnnnuummbbeerreedd --ffdduummpp--ttrraannssllaattiioonn--uunniitt[--_n]
--ffdduummpp--ccllaassss--hhiieerraarrcchhyy[--_n]
--ffdduummpp--iippaa--aallll --ffdduummpp--iippaa--ccggrraapphh
--ffdduummpp--ttrreeee--aallll
--ffdduummpp--ttrreeee--oorriiggiinnaall[--_n]
--ffdduummpp--ttrreeee--ooppttiimmiizzeedd[--_n]
--ffdduummpp--ttrreeee--iinnlliinneedd[--_n]
--ffdduummpp--ttrreeee--ccffgg --ffdduummpp--ttrreeee--vvccgg --ffdduummpp--ttrreeee--aalliiaass
--ffdduummpp--ttrreeee--cchh
--ffdduummpp--ttrreeee--ssssaa[--_n] --ffdduummpp--ttrreeee--pprree[--_n]
--ffdduummpp--ttrreeee--ccccpp[--_n] --ffdduummpp--ttrreeee--ddccee[--_n]
--ffdduummpp--ttrreeee--ggiimmppllee[--rraaww] --ffdduummpp--ttrreeee--mmuuddffllaapp[--_n]
--ffdduummpp--ttrreeee--ddoomm[--_n]
--ffdduummpp--ttrreeee--ddssee[--_n]
--ffdduummpp--ttrreeee--pphhiioopptt[--_n]
--ffdduummpp--ttrreeee--ffoorrwwpprroopp[--_n]
--ffdduummpp--ttrreeee--ccooppyyrreennaammee[--_n]
--ffdduummpp--ttrreeee--nnrrvv --ffdduummpp--ttrreeee--vveecctt
--ffdduummpp--ttrreeee--ssiinnkk
--ffdduummpp--ttrreeee--ssrraa[--_n]
--ffdduummpp--ttrreeee--ssaalliiaass
--ffdduummpp--ttrreeee--ffrree[--_n]
--ffdduummpp--ttrreeee--vvrrpp[--_n]
--ffttrreeee--vveeccttoorriizzeerr--vveerrbboossee==_n
--ffdduummpp--ttrreeee--ssttoorreeccccpp[--_n]
--ffeelliimmiinnaattee--ddwwaarrff22--dduuppss --ffeelliimmiinnaattee--uunnuusseedd--ddeebbuugg--ttyyppeess
--ffeelliimmiinnaattee--uunnuusseedd--ddeebbuugg--ssyymmbboollss --ffmmeemm--rreeppoorrtt --ffpprrooffiillee--aarrccss
--ffrraannddoomm--sseeeedd==_s_t_r_i_n_g --ffsscchheedd--vveerrbboossee==_n
--fftteesstt--ccoovveerraaggee --ffttiimmee--rreeppoorrtt --ffvvaarr--ttrraacckkiinngg
--gg --gg_l_e_v_e_l --ggccooffff --ggddwwaarrff--22
--ggggddbb --ggssttaabbss --ggssttaabbss++ --ggvvmmss --ggxxccooffff --ggxxccooffff++
--pp --ppgg --pprriinntt--ffiillee--nnaammee==_l_i_b_r_a_r_y --pprriinntt--lliibbggcccc--ffiillee--nnaammee
--pprriinntt--mmuullttii--ddiirreeccttoorryy --pprriinntt--mmuullttii--lliibb
--pprriinntt--pprroogg--nnaammee==_p_r_o_g_r_a_m --pprriinntt--sseeaarrcchh--ddiirrss --QQ
--ssaavvee--tteemmppss --ttiimmee
-
_O_p_t_i_m_i_z_a_t_i_o_n _O_p_t_i_o_n_s
--ffaalliiggnn--ffuunnccttiioonnss==_n --ffaalliiggnn--jjuummppss==_n
-
--ffaalliiggnn--llaabbeellss==_n --ffaalliiggnn--llooooppss==_n
--ffbboouunnddss--cchheecckk --ffmmuuddffllaapp --ffmmuuddffllaapptthh --ffmmuuddffllaappiirr
--ffbbrraanncchh--pprroobbaabbiilliittiieess --ffpprrooffiillee--vvaalluueess --ffvvpptt --ffbbrraanncchh--ttaarrggeett--llooaadd--ooppttiimmiizzee
--ffbbrraanncchh--ttaarrggeett--llooaadd--ooppttiimmiizzee22 --ffbbttrr--bbbb--eexxcclluussiivvee
--ffccaalllleerr--ssaavveess --ffccpprroopp--rreeggiisstteerrss --ffccssee--ffoollllooww--jjuummppss
--ffccssee--sskkiipp--bblloocckkss --ffccxx--lliimmiitteedd--rraannggee --ffddaattaa--sseeccttiioonnss
--ffddeellaayyeedd--bbrraanncchh --ffddeelleettee--nnuullll--ppooiinntteerr--cchheecckkss --ffeeaarrllyy--iinnlliinniinngg
--ffeexxppeennssiivvee--ooppttiimmiizzaattiioonnss --ffffaasstt--mmaatthh --ffffllooaatt--ssttoorree
--ffffoorrccee--aaddddrr --ffffuunnccttiioonn--sseeccttiioonnss
--ffggccssee --ffggccssee--llmm --ffggccssee--ssmm --ffggccssee--llaass --ffggccssee--aafftteerr--rreellooaadd
--fflloooopp--ooppttiimmiizzee --ffccrroossssjjuummppiinngg --ffiiff--ccoonnvveerrssiioonn --ffiiff--ccoonnvveerrssiioonn22
--ffiinnlliinnee--ffuunnccttiioonnss --ffiinnlliinnee--ffuunnccttiioonnss--ccaalllleedd--oonnccee
--ffiinnlliinnee--lliimmiitt==_n --ffkkeeeepp--iinnlliinnee--ffuunnccttiioonnss
--ffkkeeeepp--ssttaattiicc--ccoonnssttss --ffmmeerrggee--ccoonnssttaannttss --ffmmeerrggee--aallll--ccoonnssttaannttss
--ffmmoodduulloo--sscchheedd --ffnnoo--bbrraanncchh--ccoouunntt--rreegg
--ffnnoo--ddeeffaauulltt--iinnlliinnee --ffnnoo--ddeeffeerr--ppoopp --fflloooopp--ooppttiimmiizzee22 --ffmmoovvee--lloooopp--iinnvvaarriiaannttss
--ffnnoo--ffuunnccttiioonn--ccssee --ffnnoo--gguueessss--bbrraanncchh--pprroobbaabbiilliittyy
--ffnnoo--iinnlliinnee --ffnnoo--mmaatthh--eerrrrnnoo --ffnnoo--ppeeeepphhoollee --ffnnoo--ppeeeepphhoollee22
--ffuunnssaaffee--mmaatthh--ooppttiimmiizzaattiioonnss --ffuunnssaaffee--lloooopp--ooppttiimmiizzaattiioonnss --ffffiinniittee--mmaatthh--oonnllyy
--ffnnoo--ttrraappppiinngg--mmaatthh --ffnnoo--zzeerroo--iinniittiiaalliizzeedd--iinn--bbssss
--ffoommiitt--ffrraammee--ppooiinntteerr --ffooppttiimmiizzee--rreeggiisstteerr--mmoovvee
--ffooppttiimmiizzee--ssiibblliinngg--ccaallllss --ffpprreeffeettcchh--lloooopp--aarrrraayyss
--ffpprrooffiillee--ggeenneerraattee --ffpprrooffiillee--uussee
--ffrreeggmmoovvee --ffrreennaammee--rreeggiisstteerrss
--ffrreeoorrddeerr--bblloocckkss --ffrreeoorrddeerr--bblloocckkss--aanndd--ppaarrttiittiioonn --ffrreeoorrddeerr--ffuunnccttiioonnss
--ffrreerruunn--ccssee--aafftteerr--lloooopp --ffrreerruunn--lloooopp--oopptt
--ffrroouunnddiinngg--mmaatthh --ffsscchheedduullee--iinnssnnss --ffsscchheedduullee--iinnssnnss22
--ffnnoo--sscchheedd--iinntteerrbblloocckk --ffnnoo--sscchheedd--ssppeecc --ffsscchheedd--ssppeecc--llooaadd
--ffsscchheedd--ssppeecc--llooaadd--ddaannggeerroouuss
--ffsscchheedd--ssttaalllleedd--iinnssnnss==_n --ffsscchheedd--ssttaalllleedd--iinnssnnss--ddeepp==_n
--ffsscchheedd22--uussee--ssuuppeerrbblloocckkss
--ffsscchheedd22--uussee--ttrraacceess --ffrreesscchheedduullee--mmoodduulloo--sscchheedduulleedd--llooooppss
--ffssiiggnnaalliinngg--nnaannss --ffssiinnggllee--pprreecciissiioonn--ccoonnssttaanntt
--ffssttaacckk--pprrootteeccttoorr --ffssttaacckk--pprrootteeccttoorr--aallll
--ffssttrreennggtthh--rreedduuccee --ffssttrriicctt--aalliiaassiinngg --ffttrraacceerr --fftthhrreeaadd--jjuummppss
--ffuunnrroollll--aallll--llooooppss --ffuunnrroollll--llooooppss --ffppeeeell--llooooppss
--ffsspplliitt--iivvss--iinn--uunnrroolllleerr --ffuunnsswwiittcchh--llooooppss
--ffvvaarriiaabbllee--eexxppaannssiioonn--iinn--uunnrroolllleerr
--ffttrreeee--pprree --ffttrreeee--ccccpp --ffttrreeee--ddccee --ffttrreeee--lloooopp--ooppttiimmiizzee
--ffttrreeee--lloooopp--lliinneeaarr --ffttrreeee--lloooopp--iimm --ffttrreeee--lloooopp--iivvccaannoonn --ffiivvooppttss
--ffttrreeee--ddoommiinnaattoorr--ooppttss --ffttrreeee--ddssee --ffttrreeee--ccooppyyrreennaammee --ffttrreeee--ssiinnkk
--ffttrreeee--cchh --ffttrreeee--ssrraa --ffttrreeee--tteerr --ffttrreeee--llrrss --ffttrreeee--ffrree --ffttrreeee--vveeccttoorriizzee
--ffttrreeee--vveecctt--lloooopp--vveerrssiioonn --ffttrreeee--ssaalliiaass --ffwweebb
--ffttrreeee--ccooppyy--pprroopp --ffttrreeee--ssttoorree--ccccpp --ffttrreeee--ssttoorree--ccooppyy--pprroopp --ffwwhhoollee--pprrooggrraamm
----ppaarraamm _n_a_m_e==_v_a_l_u_e
--OO --OO00 --OO11 --OO22 --OO33 --OOss
-
_P_r_e_p_r_o_c_e_s_s_o_r _O_p_t_i_o_n_s
--AA_q_u_e_s_t_i_o_n==_a_n_s_w_e_r
-
--AA--_q_u_e_s_t_i_o_n[==_a_n_s_w_e_r]
--CC --ddDD --ddII --ddMM --ddNN
--DD_m_a_c_r_o[==_d_e_f_n] --EE --HH
--iiddiirraafftteerr _d_i_r
--iinncclluuddee _f_i_l_e --iimmaaccrrooss _f_i_l_e
--iipprreeffiixx _f_i_l_e --iiwwiitthhpprreeffiixx _d_i_r
--iiwwiitthhpprreeffiixxbbeeffoorree _d_i_r --iissyysstteemm _d_i_r
--iissyyssrroooott _d_i_r
--MM --MMMM --MMFF --MMGG --MMPP --MMQQ --MMTT --nnoossttddiinncc
--PP --ffwwoorrkkiinngg--ddiirreeccttoorryy --rreemmaapp
--ttrriiggrraapphhss --uunnddeeff --UU_m_a_c_r_o --WWpp,,_o_p_t_i_o_n
--XXpprreepprroocceessssoorr _o_p_t_i_o_n
-
_A_s_s_e_m_b_l_e_r _O_p_t_i_o_n
--WWaa,,_o_p_t_i_o_n --XXaasssseemmbblleerr _o_p_t_i_o_n
-
-
_L_i_n_k_e_r _O_p_t_i_o_n_s
_o_b_j_e_c_t_-_f_i_l_e_-_n_a_m_e --ll_l_i_b_r_a_r_y
-
--nnoossttaarrttffiilleess --nnooddeeffaauullttlliibbss --nnoossttddlliibb --ppiiee --rrddyynnaammiicc
--ss --ssttaattiicc --ssttaattiicc--lliibbggcccc --sshhaarreedd --sshhaarreedd--lliibbggcccc --ssyymmbboolliicc
--WWll,,_o_p_t_i_o_n --XXlliinnkkeerr _o_p_t_i_o_n
--uu _s_y_m_b_o_l
-
_D_i_r_e_c_t_o_r_y _O_p_t_i_o_n_s
--BB_p_r_e_f_i_x --II_d_i_r --iiqquuoottee_d_i_r --LL_d_i_r
-
--ssppeeccss==_f_i_l_e --II-- ----ssyyssrroooott==_d_i_r
-
_T_a_r_g_e_t _O_p_t_i_o_n_s
--VV _v_e_r_s_i_o_n --bb _m_a_c_h_i_n_e
-
-
_M_a_c_h_i_n_e _D_e_p_e_n_d_e_n_t _O_p_t_i_o_n_s
_A_R_C _O_p_t_i_o_n_s
-
--EEBB --EELL
--mmmmaannggllee--ccppuu --mmccppuu==_c_p_u --mmtteexxtt==_t_e_x_t_-_s_e_c_t_i_o_n
--mmddaattaa==_d_a_t_a_-_s_e_c_t_i_o_n --mmrrooddaattaa==_r_e_a_d_o_n_l_y_-_d_a_t_a_-_s_e_c_t_i_o_n
_A_R_M _O_p_t_i_o_n_s
--mmaappccss--ffrraammee --mmnnoo--aappccss--ffrraammee
--mmaabbii==_n_a_m_e
--mmaappccss--ssttaacckk--cchheecckk --mmnnoo--aappccss--ssttaacckk--cchheecckk
--mmaappccss--ffllooaatt --mmnnoo--aappccss--ffllooaatt
--mmaappccss--rreeeennttrraanntt --mmnnoo--aappccss--rreeeennttrraanntt
--mmsscchheedd--pprroolloogg --mmnnoo--sscchheedd--pprroolloogg
--mmlliittttllee--eennddiiaann --mmbbiigg--eennddiiaann --mmwwoorrddss--lliittttllee--eennddiiaann
--mmffllooaatt--aabbii==_n_a_m_e --mmssoofftt--ffllooaatt --mmhhaarrdd--ffllooaatt --mmffppee
--mmtthhuummbb--iinntteerrwwoorrkk --mmnnoo--tthhuummbb--iinntteerrwwoorrkk
--mmccppuu==_n_a_m_e --mmaarrcchh==_n_a_m_e --mmffppuu==_n_a_m_e
--mmssttrruuccttuurree--ssiizzee--bboouunnddaarryy==_n
--mmaabboorrtt--oonn--nnoorreettuurrnn
--mmlloonngg--ccaallllss --mmnnoo--lloonngg--ccaallllss
--mmssiinnggllee--ppiicc--bbaassee --mmnnoo--ssiinnggllee--ppiicc--bbaassee
--mmppiicc--rreeggiisstteerr==_r_e_g
--mmnnoopp--ffuunn--ddlllliimmppoorrtt
--mmcciirrrruuss--ffiixx--iinnvvaalliidd--iinnssnnss --mmnnoo--cciirrrruuss--ffiixx--iinnvvaalliidd--iinnssnnss
--mmppookkee--ffuunnccttiioonn--nnaammee
--mmtthhuummbb --mmaarrmm
--mmttppccss--ffrraammee --mmttppccss--lleeaaff--ffrraammee
--mmccaalllleerr--ssuuppeerr--iinntteerrwwoorrkkiinngg --mmccaalllleeee--ssuuppeerr--iinntteerrwwoorrkkiinngg
--mmttpp==_n_a_m_e
_A_V_R _O_p_t_i_o_n_s
--mmmmccuu==_m_c_u --mmssiizzee --mmiinniitt--ssttaacckk==_n --mmnnoo--iinntteerrrruuppttss
--mmccaallll--pprroolloogguueess --mmnnoo--ttaabblleejjuummpp --mmttiinnyy--ssttaacckk --mmiinntt88
_B_l_a_c_k_f_i_n _O_p_t_i_o_n_s
--mmoommiitt--lleeaaff--ffrraammee--ppooiinntteerr --mmnnoo--oommiitt--lleeaaff--ffrraammee--ppooiinntteerr
--mmssppeecclldd--aannoommaallyy --mmnnoo--ssppeecclldd--aannoommaallyy --mmccssyynncc--aannoommaallyy --mmnnoo--ccssyynncc--aannoommaallyy
--mmllooww--6644kk --mmnnoo--llooww6644kk --mmiidd--sshhaarreedd--lliibbrraarryy
--mmnnoo--iidd--sshhaarreedd--lliibbrraarryy --mmsshhaarreedd--lliibbrraarryy--iidd==_n
--mmlloonngg--ccaallllss --mmnnoo--lloonngg--ccaallllss
_C_R_I_S _O_p_t_i_o_n_s
--mmccppuu==_c_p_u --mmaarrcchh==_c_p_u --mmttuunnee==_c_p_u
--mmmmaaxx--ssttaacckk--ffrraammee==_n --mmeelliinnuuxx--ssttaacckkssiizzee==_n
--mmeettrraaxx44 --mmeettrraaxx110000 --mmppddeebbuugg --mmcccc--iinniitt --mmnnoo--ssiiddee--eeffffeeccttss
--mmssttaacckk--aalliiggnn --mmddaattaa--aalliiggnn --mmccoonnsstt--aalliiggnn
--mm3322--bbiitt --mm1166--bbiitt --mm88--bbiitt --mmnnoo--pprroolloogguuee--eeppiilloogguuee --mmnnoo--ggoottpplltt
--mmeellff --mmaaoouutt --mmeelliinnuuxx --mmlliinnuuxx --ssiimm --ssiimm22
--mmmmuull--bbuugg--wwoorrkkaarroouunndd --mmnnoo--mmuull--bbuugg--wwoorrkkaarroouunndd
_C_R_X _O_p_t_i_o_n_s
--mmmmaacc --mmppuusshh--aarrggss
_D_a_r_w_i_n _O_p_t_i_o_n_s
--aallll__llooaadd --aalllloowwaabbllee__cclliieenntt --aarrcchh --aarrcchh__eerrrroorrss__ffaattaall
--aarrcchh__oonnllyy --bbiinndd__aatt__llooaadd --bbuunnddllee --bbuunnddllee__llooaaddeerr
--cclliieenntt__nnaammee --ccoommppaattiibbiilliittyy__vveerrssiioonn --ccuurrrreenntt__vveerrssiioonn
--ddeeaadd__ssttrriipp
--ddeeppeennddeennccyy--ffiillee --ddyylliibb__ffiillee --ddyylliinnkkeerr__iinnssttaallll__nnaammee
--ddyynnaammiicc --ddyynnaammiicclliibb --eexxppoorrtteedd__ssyymmbboollss__lliisstt
--ffiilleelliisstt --ffllaatt__nnaammeessppaaccee --ffoorrccee__ccppuussuubbttyyppee__AALLLL
--ffoorrccee__ffllaatt__nnaammeessppaaccee --hheeaaddeerrppaadd__mmaaxx__iinnssttaallll__nnaammeess
--iimmaaggee__bbaassee --iinniitt --iinnssttaallll__nnaammee --kkeeeepp__pprriivvaattee__eexxtteerrnnss
--mmuullttii__mmoodduullee --mmuullttiippllyy__ddeeffiinneedd --mmuullttiippllyy__ddeeffiinneedd__uunnuusseedd
--nnooaallll__llooaadd --nnoo__ddeeaadd__ssttrriipp__iinniittss__aanndd__tteerrmmss
--nnooffiixxpprreebbiinnddiinngg --nnoommuullttiiddeeffss --nnoopprreebbiinndd --nnoosseegglliinnkkeeddiitt
--ppaaggeezzeerroo__ssiizzee --pprreebbiinndd --pprreebbiinndd__aallll__ttwwoolleevveell__mmoodduulleess
--pprriivvaattee__bbuunnddllee --rreeaadd__oonnllyy__rreellooccss --sseeccttaalliiggnn
--sseeccttoobbjjeeccttssyymmbboollss --wwhhyyllooaadd --sseegg11aaddddrr
--sseeccttccrreeaattee --sseeccttoobbjjeeccttssyymmbboollss --sseeccttoorrddeerr
--sseeggaaddddrr --sseeggss__rreeaadd__oonnllyy__aaddddrr --sseeggss__rreeaadd__wwrriittee__aaddddrr
--sseegg__aaddddrr__ttaabbllee --sseegg__aaddddrr__ttaabbllee__ffiilleennaammee --sseegglliinnkkeeddiitt
--sseeggpprroott --sseeggss__rreeaadd__oonnllyy__aaddddrr --sseeggss__rreeaadd__wwrriittee__aaddddrr
--ssiinnggllee__mmoodduullee --ssttaattiicc --ssuubb__lliibbrraarryy --ssuubb__uummbbrreellllaa
--ttwwoolleevveell__nnaammeessppaaccee --uummbbrreellllaa --uunnddeeffiinneedd
--uunneexxppoorrtteedd__ssyymmbboollss__lliisstt --wweeaakk__rreeffeerreennccee__mmiissmmaattcchheess
--wwhhaattssllooaaddeedd --FF --gguusseedd --ggffuullll --mmmmaaccoossxx--vveerrssiioonn--mmiinn==_v_e_r_s_i_o_n
--mmoonnee--bbyyttee--bbooooll
_D_E_C _A_l_p_h_a _O_p_t_i_o_n_s
--mmnnoo--ffpp--rreeggss --mmssoofftt--ffllooaatt --mmaallpphhaa--aass --mmggaass
--mmiieeeeee --mmiieeeeee--wwiitthh--iinneexxaacctt --mmiieeeeee--ccoonnffoorrmmaanntt
--mmffpp--ttrraapp--mmooddee==_m_o_d_e --mmffpp--rroouunnddiinngg--mmooddee==_m_o_d_e
--mmttrraapp--pprreecciissiioonn==_m_o_d_e --mmbbuuiilldd--ccoonnssttaannttss
--mmccppuu==_c_p_u_-_t_y_p_e --mmttuunnee==_c_p_u_-_t_y_p_e
--mmbbwwxx --mmmmaaxx --mmffiixx --mmcciixx
--mmffllooaatt--vvaaxx --mmffllooaatt--iieeeeee
--mmeexxpplliicciitt--rreellooccss --mmssmmaallll--ddaattaa --mmllaarrggee--ddaattaa
--mmssmmaallll--tteexxtt --mmllaarrggee--tteexxtt
--mmmmeemmoorryy--llaatteennccyy==_t_i_m_e
_D_E_C _A_l_p_h_a_/_V_M_S _O_p_t_i_o_n_s
--mmvvmmss--rreettuurrnn--ccooddeess
_F_R_V _O_p_t_i_o_n_s
--mmggpprr--3322 --mmggpprr--6644 --mmffpprr--3322 --mmffpprr--6644
--mmhhaarrdd--ffllooaatt --mmssoofftt--ffllooaatt
--mmaalllloocc--cccc --mmffiixxeedd--cccc --mmddwwoorrdd --mmnnoo--ddwwoorrdd
--mmddoouubbllee --mmnnoo--ddoouubbllee
--mmmmeeddiiaa --mmnnoo--mmeeddiiaa --mmmmuullaadddd --mmnnoo--mmuullaadddd
--mmffddppiicc --mmiinnlliinnee--pplltt --mmggpprreell--rroo --mmuullttiilliibb--lliibbrraarryy--ppiicc
--mmlliinnkkeedd--ffpp --mmlloonngg--ccaallllss --mmaalliiggnn--llaabbeellss
--mmlliibbrraarryy--ppiicc --mmaacccc--44 --mmaacccc--88
--mmppaacckk --mmnnoo--ppaacckk --mmnnoo--eeffllaaggss --mmccoonndd--mmoovvee --mmnnoo--ccoonndd--mmoovvee
--mmooppttiimmiizzee--mmeemmbbaarr --mmnnoo--ooppttiimmiizzee--mmeemmbbaarr
--mmsscccc --mmnnoo--sscccc --mmccoonndd--eexxeecc --mmnnoo--ccoonndd--eexxeecc
--mmvvlliiww--bbrraanncchh --mmnnoo--vvlliiww--bbrraanncchh
--mmmmuullttii--ccoonndd--eexxeecc --mmnnoo--mmuullttii--ccoonndd--eexxeecc --mmnneesstteedd--ccoonndd--eexxeecc
--mmnnoo--nneesstteedd--ccoonndd--eexxeecc --mmttoommccaatt--ssttaattss
--mmTTLLSS --mmttllss
--mmccppuu==_c_p_u
_H_8_/_3_0_0 _O_p_t_i_o_n_s
--mmrreellaaxx --mmhh --mmss --mmnn --mmiinntt3322 --mmaalliiggnn--330000
_H_P_P_A _O_p_t_i_o_n_s
--mmaarrcchh==_a_r_c_h_i_t_e_c_t_u_r_e_-_t_y_p_e
--mmbbiigg--sswwiittcchh --mmddiissaabbllee--ffpprreeggss --mmddiissaabbllee--iinnddeexxiinngg
--mmffaasstt--iinnddiirreecctt--ccaallllss --mmggaass --mmggnnuu--lldd --mmhhpp--lldd
--mmffiixxeedd--rraannggee==_r_e_g_i_s_t_e_r_-_r_a_n_g_e
--mmjjuummpp--iinn--ddeellaayy --mmlliinnkkeerr--oopptt --mmlloonngg--ccaallllss
--mmlloonngg--llooaadd--ssttoorree --mmnnoo--bbiigg--sswwiittcchh --mmnnoo--ddiissaabbllee--ffpprreeggss
--mmnnoo--ddiissaabbllee--iinnddeexxiinngg --mmnnoo--ffaasstt--iinnddiirreecctt--ccaallllss --mmnnoo--ggaass
--mmnnoo--jjuummpp--iinn--ddeellaayy --mmnnoo--lloonngg--llooaadd--ssttoorree
--mmnnoo--ppoorrttaabbllee--rruunnttiimmee --mmnnoo--ssoofftt--ffllooaatt
--mmnnoo--ssppaaccee--rreeggss --mmssoofftt--ffllooaatt --mmppaa--rriisscc--11--00
--mmppaa--rriisscc--11--11 --mmppaa--rriisscc--22--00 --mmppoorrttaabbllee--rruunnttiimmee
--mmsscchheedduullee==_c_p_u_-_t_y_p_e --mmssppaaccee--rreeggss --mmssiioo --mmwwssiioo
--mmuunniixx==_u_n_i_x_-_s_t_d --nnoolliibbddlldd --ssttaattiicc --tthhrreeaaddss
_i_3_8_6 _a_n_d _x_8_6_-_6_4 _O_p_t_i_o_n_s
--mmttuunnee==_c_p_u_-_t_y_p_e --mmaarrcchh==_c_p_u_-_t_y_p_e
--mmffppmmaatthh==_u_n_i_t
--mmaassmm==_d_i_a_l_e_c_t --mmnnoo--ffaannccyy--mmaatthh--338877
--mmnnoo--ffpp--rreett--iinn--338877 --mmssoofftt--ffllooaatt --mmssvvrr33--sshhlliibb
--mmnnoo--wwiiddee--mmuullttiippllyy --mmrrttdd --mmaalliiggnn--ddoouubbllee
--mmpprreeffeerrrreedd--ssttaacckk--bboouunnddaarryy==_n_u_m
--mmmmmmxx --mmssssee --mmssssee22 --mmssssee33 --mm33ddnnooww
--mmtthhrreeaaddss --mmnnoo--aalliiggnn--ssttrriinnggooppss --mmiinnlliinnee--aallll--ssttrriinnggooppss
--mmppuusshh--aarrggss --mmaaccccuummuullaattee--oouuttggooiinngg--aarrggss --mm112288bbiitt--lloonngg--ddoouubbllee
--mm9966bbiitt--lloonngg--ddoouubbllee --mmrreeggppaarrmm==_n_u_m --mmsssseerreeggppaarrmm
--mmoommiitt--lleeaaff--ffrraammee--ppooiinntteerr --mmnnoo--rreedd--zzoonnee --mmnnoo--ttllss--ddiirreecctt--sseegg--rreeffss
--mmccmmooddeell==_c_o_d_e_-_m_o_d_e_l
--mm3322 --mm6644 --mmllaarrggee--ddaattaa--tthhrreesshhoolldd==_n_u_m
_I_A_-_6_4 _O_p_t_i_o_n_s
--mmbbiigg--eennddiiaann --mmlliittttllee--eennddiiaann --mmggnnuu--aass --mmggnnuu--lldd --mmnnoo--ppiicc
--mmvvoollaattiillee--aassmm--ssttoopp --mmrreeggiisstteerr--nnaammeess --mmnnoo--ssddaattaa
--mmccoonnssttaanntt--ggpp --mmaauuttoo--ppiicc --mmiinnlliinnee--ffllooaatt--ddiivviiddee--mmiinn--llaatteennccyy
--mmiinnlliinnee--ffllooaatt--ddiivviiddee--mmaaxx--tthhrroouugghhppuutt
--mmiinnlliinnee--iinntt--ddiivviiddee--mmiinn--llaatteennccyy
--mmiinnlliinnee--iinntt--ddiivviiddee--mmaaxx--tthhrroouugghhppuutt
--mmiinnlliinnee--ssqqrrtt--mmiinn--llaatteennccyy --mmiinnlliinnee--ssqqrrtt--mmaaxx--tthhrroouugghhppuutt
--mmnnoo--ddwwaarrff22--aassmm --mmeeaarrllyy--ssttoopp--bbiittss
--mmffiixxeedd--rraannggee==_r_e_g_i_s_t_e_r_-_r_a_n_g_e --mmttllss--ssiizzee==_t_l_s_-_s_i_z_e
--mmttuunnee==_c_p_u_-_t_y_p_e --mmtt --pptthhrreeaadd --mmiillpp3322 --mmllpp6644
_M_3_2_R_/_D _O_p_t_i_o_n_s
--mm3322rr22 --mm3322rrxx --mm3322rr
--mmddeebbuugg
--mmaalliiggnn--llooooppss --mmnnoo--aalliiggnn--llooooppss
--mmiissssuuee--rraattee==_n_u_m_b_e_r
--mmbbrraanncchh--ccoosstt==_n_u_m_b_e_r
--mmmmooddeell==_c_o_d_e_-_s_i_z_e_-_m_o_d_e_l_-_t_y_p_e
--mmssddaattaa==_s_d_a_t_a_-_t_y_p_e
--mmnnoo--fflluusshh--ffuunncc --mmfflluusshh--ffuunncc==_n_a_m_e
--mmnnoo--fflluusshh--ttrraapp --mmfflluusshh--ttrraapp==_n_u_m_b_e_r
--GG _n_u_m
_M_3_2_C _O_p_t_i_o_n_s
--mmccppuu==_c_p_u --mmssiimm --mmeemmrreeggss==_n_u_m_b_e_r
_M_6_8_0_x_0 _O_p_t_i_o_n_s
--mm6688000000 --mm6688002200 --mm6688002200--4400 --mm6688002200--6600 --mm6688003300 --mm6688004400
--mm6688006600 --mmccppuu3322 --mm55220000 --mm6688888811 --mmbbiittffiieelldd --mmcc6688000000 --mmcc6688002200
--mmnnoobbiittffiieelldd --mmrrttdd --mmsshhoorrtt --mmssoofftt--ffllooaatt --mmppccrreell
--mmaalliiggnn--iinntt --mmssttrriicctt--aalliiggnn --mmsseepp--ddaattaa --mmnnoo--sseepp--ddaattaa
--mmsshhaarreedd--lliibbrraarryy--iidd==nn --mmiidd--sshhaarreedd--lliibbrraarryy --mmnnoo--iidd--sshhaarreedd--lliibbrraarryy
_M_6_8_h_c_1_x _O_p_t_i_o_n_s
--mm66881111 --mm66881122 --mm6688hhcc1111 --mm6688hhcc1122 --mm6688hhccss1122
--mmaauuttoo--iinnccddeecc --mmiinnmmaaxx --mmlloonngg--ccaallllss --mmsshhoorrtt
--mmssoofftt--rreegg--ccoouunntt==_c_o_u_n_t
_M_C_o_r_e _O_p_t_i_o_n_s
--mmhhaarrddlliitt --mmnnoo--hhaarrddlliitt --mmddiivv --mmnnoo--ddiivv --mmrreellaaxx--iimmmmeeddiiaatteess
--mmnnoo--rreellaaxx--iimmmmeeddiiaatteess --mmwwiiddee--bbiittffiieellddss --mmnnoo--wwiiddee--bbiittffiieellddss
--mm44bbyyttee--ffuunnccttiioonnss --mmnnoo--44bbyyttee--ffuunnccttiioonnss --mmccaallllggrraapphh--ddaattaa
--mmnnoo--ccaallllggrraapphh--ddaattaa --mmssllooww--bbyytteess --mmnnoo--ssllooww--bbyytteess --mmnnoo--llssiimm
--mmlliittttllee--eennddiiaann --mmbbiigg--eennddiiaann --mm221100 --mm334400 --mmssttaacckk--iinnccrreemmeenntt
_M_I_P_S _O_p_t_i_o_n_s
--EELL --EEBB --mmaarrcchh==_a_r_c_h --mmttuunnee==_a_r_c_h
--mmiippss11 --mmiippss22 --mmiippss33 --mmiippss44 --mmiippss3322 --mmiippss3322rr22 --mmiippss6644
--mmiippss1166 --mmnnoo--mmiippss1166 --mmaabbii==_a_b_i --mmaabbiiccaallllss --mmnnoo--aabbiiccaallllss
--mmxxggoott --mmnnoo--xxggoott --mmggpp3322 --mmggpp6644 --mmffpp3322 --mmffpp6644
--mmhhaarrdd--ffllooaatt --mmssoofftt--ffllooaatt --mmssiinnggllee--ffllooaatt --mmddoouubbllee--ffllooaatt
--mmddsspp --mmppaaiirreedd--ssiinnggllee --mmiippss33dd
--mmlloonngg6644 --mmlloonngg3322 --mmssyymm3322 --mmnnoo--ssyymm3322
--GG_n_u_m --mmeemmbbeeddddeedd--ddaattaa --mmnnoo--eemmbbeeddddeedd--ddaattaa
--mmuunniinniitt--ccoonnsstt--iinn--rrooddaattaa --mmnnoo--uunniinniitt--ccoonnsstt--iinn--rrooddaattaa
--mmsspplliitt--aaddddrreesssseess --mmnnoo--sspplliitt--aaddddrreesssseess
--mmeexxpplliicciitt--rreellooccss --mmnnoo--eexxpplliicciitt--rreellooccss
--mmcchheecckk--zzeerroo--ddiivviissiioonn --mmnnoo--cchheecckk--zzeerroo--ddiivviissiioonn
--mmddiivviiddee--ttrraappss --mmddiivviiddee--bbrreeaakkss
--mmmmeemmccppyy --mmnnoo--mmeemmccppyy --mmlloonngg--ccaallllss --mmnnoo--lloonngg--ccaallllss
--mmmmaadd --mmnnoo--mmaadd --mmffuusseedd--mmaadddd --mmnnoo--ffuusseedd--mmaadddd --nnooccpppp
--mmffiixx--rr44000000 --mmnnoo--ffiixx--rr44000000 --mmffiixx--rr44440000 --mmnnoo--ffiixx--rr44440000
--mmffiixx--vvrr44112200 --mmnnoo--ffiixx--vvrr44112200 --mmffiixx--vvrr44113300
--mmffiixx--ssbb11 --mmnnoo--ffiixx--ssbb11
--mmfflluusshh--ffuunncc==_f_u_n_c --mmnnoo--fflluusshh--ffuunncc
--mmbbrraanncchh--lliikkeellyy --mmnnoo--bbrraanncchh--lliikkeellyy
--mmffpp--eexxcceeppttiioonnss --mmnnoo--ffpp--eexxcceeppttiioonnss
--mmvvrr44113300--aalliiggnn --mmnnoo--vvrr44113300--aalliiggnn
_M_M_I_X _O_p_t_i_o_n_s
--mmlliibbffuunnccss --mmnnoo--lliibbffuunnccss --mmeeppssiilloonn --mmnnoo--eeppssiilloonn --mmaabbii==ggnnuu
--mmaabbii==mmmmiixxwwaarree --mmzzeerroo--eexxtteenndd --mmkknnuutthhddiivv --mmttoopplleevveell--ssyymmbboollss
--mmeellff --mmbbrraanncchh--pprreeddiicctt --mmnnoo--bbrraanncchh--pprreeddiicctt --mmbbaassee--aaddddrreesssseess
--mmnnoo--bbaassee--aaddddrreesssseess --mmssiinnggllee--eexxiitt --mmnnoo--ssiinnggllee--eexxiitt
_M_N_1_0_3_0_0 _O_p_t_i_o_n_s
--mmmmuulltt--bbuugg --mmnnoo--mmuulltt--bbuugg
--mmaamm3333 --mmnnoo--aamm3333
--mmaamm3333--22 --mmnnoo--aamm3333--22
--mmrreettuurrnn--ppooiinntteerr--oonn--dd00
--mmnnoo--ccrrtt00 --mmrreellaaxx
_M_T _O_p_t_i_o_n_s
--mmnnoo--ccrrtt00 --mmbbaacccc --mmssiimm
--mmaarrcchh==_c_p_u_-_t_y_p_e
_P_D_P_-_1_1 _O_p_t_i_o_n_s
--mmffppuu --mmssoofftt--ffllooaatt --mmaacc00 --mmnnoo--aacc00 --mm4400 --mm4455 --mm1100
--mmbbccooppyy --mmbbccooppyy--bbuuiillttiinn --mmiinntt3322 --mmnnoo--iinntt1166
--mmiinntt1166 --mmnnoo--iinntt3322 --mmffllooaatt3322 --mmnnoo--ffllooaatt6644
--mmffllooaatt6644 --mmnnoo--ffllooaatt3322 --mmaabbsshhii --mmnnoo--aabbsshhii
--mmbbrraanncchh--eexxppeennssiivvee --mmbbrraanncchh--cchheeaapp
--mmsspplliitt --mmnnoo--sspplliitt --mmuunniixx--aassmm --mmddeecc--aassmm
_P_o_w_e_r_P_C _O_p_t_i_o_n_s
See RS/6000 and PowerPC Options.
_R_S_/_6_0_0_0 _a_n_d _P_o_w_e_r_P_C _O_p_t_i_o_n_s
--mmccppuu==_c_p_u_-_t_y_p_e
--mmttuunnee==_c_p_u_-_t_y_p_e
--mmppoowweerr --mmnnoo--ppoowweerr --mmppoowweerr22 --mmnnoo--ppoowweerr22
--mmppoowweerrppcc --mmppoowweerrppcc6644 --mmnnoo--ppoowweerrppcc
--mmaallttiivveecc --mmnnoo--aallttiivveecc
--mmppoowweerrppcc--ggppoopptt --mmnnoo--ppoowweerrppcc--ggppoopptt
--mmppoowweerrppcc--ggffxxoopptt --mmnnoo--ppoowweerrppcc--ggffxxoopptt
--mmmmffccrrff --mmnnoo--mmffccrrff --mmppooppccnnttbb --mmnnoo--ppooppccnnttbb --mmffpprrnndd --mmnnoo--ffpprrnndd
--mmnneeww--mmnneemmoonniiccss --mmoolldd--mmnneemmoonniiccss
--mmffuullll--ttoocc --mmmmiinniimmaall--ttoocc --mmnnoo--ffpp--iinn--ttoocc --mmnnoo--ssuumm--iinn--ttoocc
--mm6644 --mm3322 --mmxxll--ccoommppaatt --mmnnoo--xxll--ccoommppaatt --mmppee
--mmaalliiggnn--ppoowweerr --mmaalliiggnn--nnaattuurraall
--mmssoofftt--ffllooaatt --mmhhaarrdd--ffllooaatt --mmmmuullttiippllee --mmnnoo--mmuullttiippllee
--mmssttrriinngg --mmnnoo--ssttrriinngg --mmuuppddaattee --mmnnoo--uuppddaattee
--mmffuusseedd--mmaadddd --mmnnoo--ffuusseedd--mmaadddd --mmbbiitt--aalliiggnn --mmnnoo--bbiitt--aalliiggnn
--mmssttrriicctt--aalliiggnn --mmnnoo--ssttrriicctt--aalliiggnn --mmrreellooccaattaabbllee
--mmnnoo--rreellooccaattaabbllee --mmrreellooccaattaabbllee--lliibb --mmnnoo--rreellooccaattaabbllee--lliibb
--mmttoocc --mmnnoo--ttoocc --mmlliittttllee --mmlliittttllee--eennddiiaann --mmbbiigg --mmbbiigg--eennddiiaann
--mmddyynnaammiicc--nnoo--ppiicc --mmaallttiivveecc --mmsswwddiivv
--mmpprriioorriittiizzee--rreessttrriicctteedd--iinnssnnss==_p_r_i_o_r_i_t_y
--mmsscchheedd--ccoossttllyy--ddeepp==_d_e_p_e_n_d_e_n_c_e___t_y_p_e
--mmiinnsseerrtt--sscchheedd--nnooppss==_s_c_h_e_m_e
--mmccaallll--ssyyssvv --mmccaallll--nneettbbssdd
--mmaaiixx--ssttrruucctt--rreettuurrnn --mmssvvrr44--ssttrruucctt--rreettuurrnn
--mmaabbii==_a_b_i_-_t_y_p_e --mmsseeccuurree--pplltt --mmbbssss--pplltt
--mmiisseell --mmnnoo--iisseell
--mmiisseell==yyeess --mmiisseell==nnoo
--mmssppee --mmnnoo--ssppee
--mmssppee==yyeess --mmssppee==nnoo
--mmvvrrssaavvee --mmnnoo--vvrrssaavvee
--mmffllooaatt--ggpprrss==yyeess --mmffllooaatt--ggpprrss==nnoo --mmffllooaatt--ggpprrss==ssiinnggllee --mmffllooaatt--ggpprrss==ddoouubbllee
--mmpprroottoottyyppee --mmnnoo--pprroottoottyyppee
--mmssiimm --mmmmvvmmee --mmaaddss --mmyyeelllloowwkknniiffee --mmeemmbb --mmssddaattaa
--mmssddaattaa==_o_p_t --mmvvxxwwoorrkkss --mmwwiinnddiissss --GG _n_u_m --pptthhrreeaadd
_S_/_3_9_0 _a_n_d _z_S_e_r_i_e_s _O_p_t_i_o_n_s
--mmttuunnee==_c_p_u_-_t_y_p_e --mmaarrcchh==_c_p_u_-_t_y_p_e
--mmhhaarrdd--ffllooaatt --mmssoofftt--ffllooaatt --mmlloonngg--ddoouubbllee--6644 --mmlloonngg--ddoouubbllee--112288
--mmbbaacckkcchhaaiinn --mmnnoo--bbaacckkcchhaaiinn --mmppaacckkeedd--ssttaacckk --mmnnoo--ppaacckkeedd--ssttaacckk
--mmssmmaallll--eexxeecc --mmnnoo--ssmmaallll--eexxeecc --mmmmvvccllee --mmnnoo--mmvvccllee
--mm6644 --mm3311 --mmddeebbuugg --mmnnoo--ddeebbuugg --mmeessaa --mmzzaarrcchh
--mmttppff--ttrraaccee --mmnnoo--ttppff--ttrraaccee --mmffuusseedd--mmaadddd --mmnnoo--ffuusseedd--mmaadddd
--mmwwaarrnn--ffrraammeessiizzee --mmwwaarrnn--ddyynnaammiiccssttaacckk --mmssttaacckk--ssiizzee --mmssttaacckk--gguuaarrdd
_S_H _O_p_t_i_o_n_s
--mm11 --mm22 --mm22ee --mm33 --mm33ee
--mm44--nnooffppuu --mm44--ssiinnggllee--oonnllyy --mm44--ssiinnggllee --mm44
--mm44aa--nnooffppuu --mm44aa--ssiinnggllee--oonnllyy --mm44aa--ssiinnggllee --mm44aa --mm44aall
--mm55--6644mmeeddiiaa --mm55--6644mmeeddiiaa--nnooffppuu
--mm55--3322mmeeddiiaa --mm55--3322mmeeddiiaa--nnooffppuu
--mm55--ccoommppaacctt --mm55--ccoommppaacctt--nnooffppuu
--mmbb --mmll --mmddaalliiggnn --mmrreellaaxx
--mmbbiiggttaabbllee --mmffmmoovvdd --mmhhiittaacchhii --mmrreenneessaass --mmnnoo--rreenneessaass --mmnnoommaaccssaavvee
--mmiieeeeee --mmiissiizzee --mmppaaddssttrruucctt --mmssppaaccee
--mmpprreeffeerrggoott --mmuusseerrmmooddee --mmuullttccoosstt==_n_u_m_b_e_r --mmddiivv==_s_t_r_a_t_e_g_y
--mmddiivvssii33__lliibbffuunncc==_n_a_m_e
--mmaaddjjuusstt--uunnrroollll --mmiinnddeexxeedd--aaddddrreessssiinngg --mmggeettttrrccoosstt==_n_u_m_b_e_r --mmpptt--ffiixxeedd
--mmiinnvvaalliidd--ssyymmbboollss
_S_P_A_R_C _O_p_t_i_o_n_s
--mmccppuu==_c_p_u_-_t_y_p_e
--mmttuunnee==_c_p_u_-_t_y_p_e
--mmccmmooddeell==_c_o_d_e_-_m_o_d_e_l
--mm3322 --mm6644 --mmaapppp--rreeggss --mmnnoo--aapppp--rreeggss
--mmffaasstteerr--ssttrruuccttss --mmnnoo--ffaasstteerr--ssttrruuccttss
--mmffppuu --mmnnoo--ffppuu --mmhhaarrdd--ffllooaatt --mmssoofftt--ffllooaatt
--mmhhaarrdd--qquuaadd--ffllooaatt --mmssoofftt--qquuaadd--ffllooaatt
--mmiimmppuurree--tteexxtt --mmnnoo--iimmppuurree--tteexxtt --mmlliittttllee--eennddiiaann
--mmssttaacckk--bbiiaass --mmnnoo--ssttaacckk--bbiiaass
--mmuunnaalliiggnneedd--ddoouubblleess --mmnnoo--uunnaalliiggnneedd--ddoouubblleess
--mmvv88pplluuss --mmnnoo--vv88pplluuss --mmvviiss --mmnnoo--vviiss
--tthhrreeaaddss --pptthhrreeaaddss --pptthhrreeaadd
_S_y_s_t_e_m _V _O_p_t_i_o_n_s
--QQyy --QQnn --YYPP,,_p_a_t_h_s --YYmm,,_d_i_r
_T_M_S_3_2_0_C_3_x_/_C_4_x _O_p_t_i_o_n_s
--mmccppuu==_c_p_u --mmbbiigg --mmssmmaallll --mmrreeggppaarrmm --mmmmeemmppaarrmm
--mmffaasstt--ffiixx --mmmmppyyii --mmbbkk --mmttii --mmddpp--iissrr--rreellooaadd
--mmrrppttss==_c_o_u_n_t --mmrrppttbb --mmddbb --mmlloooopp--uunnssiiggnneedd
--mmppaarraalllleell--iinnssnnss --mmppaarraalllleell--mmppyy --mmpprreesseerrvvee--ffllooaatt
_V_8_5_0 _O_p_t_i_o_n_s
--mmlloonngg--ccaallllss --mmnnoo--lloonngg--ccaallllss --mmeepp --mmnnoo--eepp
--mmpprroolloogg--ffuunnccttiioonn --mmnnoo--pprroolloogg--ffuunnccttiioonn --mmssppaaccee
--mmttddaa==_n --mmssddaa==_n --mmzzddaa==_n
--mmaapppp--rreeggss --mmnnoo--aapppp--rreeggss
--mmddiissaabbllee--ccaalllltt --mmnnoo--ddiissaabbllee--ccaalllltt
--mmvv885500ee11
--mmvv885500ee
--mmvv885500 --mmbbiigg--sswwiittcchh
_V_A_X _O_p_t_i_o_n_s
--mmgg --mmggnnuu --mmuunniixx
_x_8_6_-_6_4 _O_p_t_i_o_n_s
See i386 and x86-64 Options.
_X_s_t_o_r_m_y_1_6 _O_p_t_i_o_n_s
--mmssiimm
_X_t_e_n_s_a _O_p_t_i_o_n_s
--mmccoonnsstt1166 --mmnnoo--ccoonnsstt1166
--mmffuusseedd--mmaadddd --mmnnoo--ffuusseedd--mmaadddd
--mmtteexxtt--sseeccttiioonn--lliitteerraallss --mmnnoo--tteexxtt--sseeccttiioonn--lliitteerraallss
--mmttaarrggeett--aalliiggnn --mmnnoo--ttaarrggeett--aalliiggnn
--mmlloonnggccaallllss --mmnnoo--lloonnggccaallllss
_z_S_e_r_i_e_s _O_p_t_i_o_n_s
See S/390 and zSeries Options.
-
_C_o_d_e _G_e_n_e_r_a_t_i_o_n _O_p_t_i_o_n_s
--ffccaallll--ssaavveedd--_r_e_g --ffccaallll--uusseedd--_r_e_g
-
--ffffiixxeedd--_r_e_g --ffeexxcceeppttiioonnss
--ffnnoonn--ccaallll--eexxcceeppttiioonnss --ffuunnwwiinndd--ttaabblleess
--ffaassyynncchhrroonnoouuss--uunnwwiinndd--ttaabblleess
--ffiinnhhiibbiitt--ssiizzee--ddiirreeccttiivvee --ffiinnssttrruummeenntt--ffuunnccttiioonnss
--ffnnoo--ccoommmmoonn --ffnnoo--iiddeenntt
--ffppcccc--ssttrruucctt--rreettuurrnn --ffppiicc --ffPPIICC --ffppiiee --ffPPIIEE
--ffnnoo--jjuummpp--ttaabblleess
--ffrreegg--ssttrruucctt--rreettuurrnn --ffsshhaarreedd--ddaattaa --ffsshhoorrtt--eennuummss
--ffsshhoorrtt--ddoouubbllee --ffsshhoorrtt--wwcchhaarr
--ffvveerrbboossee--aassmm --ffppaacckk--ssttrruucctt[[==_n]] --ffssttaacckk--cchheecckk
--ffssttaacckk--lliimmiitt--rreeggiisstteerr==_r_e_g --ffssttaacckk--lliimmiitt--ssyymmbbooll==_s_y_m
--ffaarrgguummeenntt--aalliiaass --ffaarrgguummeenntt--nnooaalliiaass
--ffaarrgguummeenntt--nnooaalliiaass--gglloobbaall --fflleeaaddiinngg--uunnddeerrssccoorree
--ffttllss--mmooddeell==_m_o_d_e_l
--ffttrraappvv --ffwwrraappvv --ffbboouunnddss--cchheecckk
--ffvviissiibbiilliittyy
OOppttiioonnss CCoonnttrroolllliinngg tthhee KKiinndd ooff OOuuttppuutt
Compilation can involve up to four stages: preprocessing, compilation
proper, assembly and linking, always in that order. GCC is capable of
preprocessing and compiling several files either into several
assembler input files, or into one assembler input file; then each
assembler input file produces an object file, and linking combines all
the object files (those newly compiled, and those specified as input)
into an executable file.
For any given input file, the file name suffix determines what kind of
compilation is done:
-
_f_i_l_e..cc
C source code which must be preprocessed.
-
-
_f_i_l_e..ii
C source code which should not be preprocessed.
-
-
_f_i_l_e..iiii
C++ source code which should not be preprocessed.
-
-
_f_i_l_e..mm
Objective-C source code. Note that you must link with the _l_i_b_o_b_j_c
-
library to make an Objective-C program work.
-
_f_i_l_e..mmii
Objective-C source code which should not be preprocessed.
-
-
_f_i_l_e..mmmm
-
-
_f_i_l_e..MM
Objective-C++ source code. Note that you must link with the _l_i_b_o_b_j_c
-
library to make an Objective-C++ program work. Note that ..MM refers
to a literal capital M.
-
_f_i_l_e..mmiiii
Objective-C++ source code which should not be preprocessed.
-
-
_f_i_l_e..hh
C, C++, Objective-C or Objective-C++ header file to be turned into a
-
precompiled header.
-
_f_i_l_e..cccc
-
-
_f_i_l_e..ccpp
-
-
_f_i_l_e..ccxxxx
-
-
_f_i_l_e..ccpppp
-
-
_f_i_l_e..CCPPPP
-
-
_f_i_l_e..cc++++
-
-
_f_i_l_e..CC
C++ source code which must be preprocessed. Note that in ..ccxxxx,
-
the last two letters must both be literally xx. Likewise,
..CC refers to a literal capital C.
-
_f_i_l_e..mmmm
-
-
_f_i_l_e..MM
Objective-C++ source code which must be preprocessed.
-
-
_f_i_l_e..mmiiii
Objective-C++ source code which should not be preprocessed.
-
-
_f_i_l_e..hhhh
-
-
_f_i_l_e..HH
C++ header file to be turned into a precompiled header.
-
-
_f_i_l_e..ff
-
-
_f_i_l_e..ffoorr
-
-
_f_i_l_e..FFOORR
Fixed form Fortran source code which should not be preprocessed.
-
-
_f_i_l_e..FF
-
-
_f_i_l_e..ffpppp
-
-
_f_i_l_e..FFPPPP
Fixed form Fortran source code which must be preprocessed (with the traditional
-
preprocessor).
-
_f_i_l_e..ff9900
-
-
_f_i_l_e..ff9955
Free form Fortran source code which should not be preprocessed.
-
-
_f_i_l_e..FF9900
-
-
_f_i_l_e..FF9955
Free form Fortran source code which must be preprocessed (with the
-
traditional preprocessor).
-
_f_i_l_e..aaddss
Ada source code file which contains a library unit declaration (a
-
declaration of a package, subprogram, or generic, or a generic
instantiation), or a library unit renaming declaration (a package,
generic, or subprogram renaming declaration). Such files are also
called _s_p_e_c_s.
-
_f_i_l_e..aaddbb
Ada source code file containing a library unit body (a subprogram or
-
package body). Such files are also called _b_o_d_i_e_s.
-
_f_i_l_e..ss
Assembler code.
-
-
_f_i_l_e..SS
Assembler code which must be preprocessed.
-
-
_o_t_h_e_r
An object file to be fed straight into linking.
-
Any file name with no recognized suffix is treated this way.
You can specify the input language explicitly with the --xx option:
-
--xx _l_a_n_g_u_a_g_e
Specify explicitly the _l_a_n_g_u_a_g_e for the following input files
-
(rather than letting the compiler choose a default based on the file
name suffix). This option applies to all following input files until
the next --xx option. Possible values for _l_a_n_g_u_a_g_e are:
c c-header c-cpp-output
c++ c++-header c++-cpp-output
objective-c objective-c-header objective-c-cpp-output
objective-c++ objective-c++-header objective-c++-cpp-output
assembler assembler-with-cpp
ada
f77 f77-cpp-input
f95 f95-cpp-input
java
treelang
-
--xx nnoonnee
Turn off any specification of a language, so that subsequent files are
-
handled according to their file name suffixes (as they are if --xx
has not been used at all).
-
--ppaassss--eexxiitt--ccooddeess
Normally the ggcccc program will exit with the code of 1 if any
-
phase of the compiler returns a non-success return code. If you specify
--ppaassss--eexxiitt--ccooddeess, the ggcccc program will instead return with
numerically highest error produced by any phase that returned an error
indication.
If you only want some of the stages of compilation, you can use
--xx (or filename suffixes) to tell ggcccc where to start, and
one of the options --cc, --SS, or --EE to say where
ggcccc is to stop. Note that some combinations (for example,
--xx ccpppp--oouuttppuutt --EE) instruct ggcccc to do nothing at all.
-
--cc
Compile or assemble the source files, but do not link. The linking
-
stage simply is not done. The ultimate output is in the form of an
object file for each source file.
By default, the object file name for a source file is made by replacing
the suffix ..cc, ..ii, ..ss, etc., with ..oo.
Unrecognized input files, not requiring compilation or assembly, are
ignored.
-
--SS
Stop after the stage of compilation proper; do not assemble. The output
-
is in the form of an assembler code file for each non-assembler input
file specified.
By default, the assembler file name for a source file is made by
replacing the suffix ..cc, ..ii, etc., with ..ss.
Input files that don't require compilation are ignored.
-
--EE
Stop after the preprocessing stage; do not run the compiler proper. The
-
output is in the form of preprocessed source code, which is sent to the
standard output.
Input files which don't require preprocessing are ignored.
-
--oo _f_i_l_e
Place output in file _f_i_l_e. This applies regardless to whatever
-
sort of output is being produced, whether it be an executable file,
an object file, an assembler file or preprocessed C code.
If --oo is not specified, the default is to put an executable
file in _a_._o_u_t, the object file for
_s_o_u_r_c_e_._s_u_f_f_i_x in _s_o_u_r_c_e_._o, its
assembler file in _s_o_u_r_c_e_._s, a precompiled header file in
_s_o_u_r_c_e_._s_u_f_f_i_x_._g_c_h, and all preprocessed C source on
standard output.
-
--vv
Print (on standard error output) the commands executed to run the stages
-
of compilation. Also print the version number of the compiler driver
program and of the preprocessor and the compiler proper.
-
--######
Like --vv except the commands are not executed and all command
-
arguments are quoted. This is useful for shell scripts to capture the
driver-generated command lines.
-
--ppiippee
Use pipes rather than temporary files for communication between the
-
various stages of compilation. This fails to work on some systems where
the assembler is unable to read from a pipe; but the GNU assembler has
no trouble.
-
--ccoommbbiinnee
If you are compiling multiple source files, this option tells the driver
-
to pass all the source files to the compiler at once (for those
languages for which the compiler can handle this). This will allow
intermodule analysis (IMA) to be performed by the compiler. Currently the only
language for which this is supported is C. If you pass source files for
multiple languages to the driver, using this option, the driver will invoke
the compiler(s) that support IMA once each, passing each compiler all the
source files appropriate for it. For those languages that do not support
IMA this option will be ignored, and the compiler will be invoked once for
each source file in that language. If you use this option in conjunction
with --ssaavvee--tteemmppss, the compiler will generate multiple
pre-processed files
(one for each source file), but only one (combined) _._o or
_._s file.
-
----hheellpp
Print (on the standard output) a description of the command line options
-
understood by ggcccc. If the --vv option is also specified
then ----hheellpp will also be passed on to the various processes
invoked by ggcccc, so that they can display the command line options
they accept. If the --WWeexxttrraa option is also specified then command
line options which have no documentation associated with them will also
be displayed.
-
----ttaarrggeett--hheellpp
Print (on the standard output) a description of target specific command
-
line options for each tool.
-
----vveerrssiioonn
Display the version number and copyrights of the invoked GCC.
-
CCoommppiilliinngg CC++++ PPrrooggrraammss
C++ source files conventionally use one of the suffixes ..CC,
..cccc, ..ccpppp, ..CCPPPP, ..cc++++, ..ccpp, or
..ccxxxx; C++ header files often use ..hhhh or ..HH; and
preprocessed C++ files use the suffix ..iiii. GCC recognizes
files with these names and compiles them as C++ programs even if you
call the compiler the same way as for compiling C programs (usually
with the name ggcccc).
However, C++ programs often require class libraries as well as a
compiler that understands the C++ language---and under some
circumstances, you might want to compile programs or header files from
standard input, or otherwise without a suffix that flags them as C++
programs. You might also like to precompile a C header file with a
..hh extension to be used in C++ compilations. gg++++ is a
program that calls GCC with the default language set to C++, and
automatically specifies linking against the C++ library. On many
systems, gg++++ is also installed with the name cc++++.
When you compile C++ programs, you may specify many of the same
command-line options that you use for compiling programs in any
language; or command-line options meaningful for C and related
languages; or options that are meaningful only for C++ programs.
OOppttiioonnss CCoonnttrroolllliinngg CC DDiiaalleecctt
The following options control the dialect of C (or languages derived
from C, such as C++, Objective-C and Objective-C++) that the compiler
accepts:
-
--aannssii
In C mode, support all ISO C90 programs. In C++ mode,
-
remove GNU extensions that conflict with ISO C++.
This turns off certain features of GCC that are incompatible with ISO
C90 (when compiling C code), or of standard C++ (when compiling C++ code),
such as the "asm" and "typeof" keywords, and
predefined macros such as "unix" and "vax" that identify the
type of system you are using. It also enables the undesirable and
rarely used ISO trigraph feature. For the C compiler,
it disables recognition of C++ style //// comments as well as
the "inline" keyword.
The alternate keywords "__asm__", "__extension__",
"__inline__" and "__typeof__" continue to work despite
--aannssii. You would not want to use them in an ISO C program, of
course, but it is useful to put them in header files that might be included
in compilations done with --aannssii. Alternate predefined macros
such as "__unix__" and "__vax__" are also available, with or
without --aannssii.
The --aannssii option does not cause non-ISO programs to be
rejected gratuitously. For that, --ppeeddaannttiicc is required in
addition to --aannssii.
The macro "__STRICT_ANSI__" is predefined when the --aannssii
option is used. Some header files may notice this macro and refrain
from declaring certain functions or defining certain macros that the
ISO standard doesn't call for; this is to avoid interfering with any
programs that might use these names for other things.
Functions which would normally be built in but do not have semantics
defined by ISO C (such as "alloca" and "ffs") are not built-in
functions with --aannssii is used.
-
--ssttdd==
Determine the language standard. This option is currently only
-
supported when compiling C or C++. A value for this option must be
provided; possible values are
-
cc8899
-
-
iissoo99889999::11999900
ISO C90 (same as --aannssii).
-
-
iissoo99889999::119999440099
ISO C90 as modified in amendment 1.
-
-
cc9999
-
-
cc99xx
-
-
iissoo99889999::11999999
-
-
iissoo99889999::119999xx
ISO C99. Note that this standard is not yet fully supported; see
-
for more information. The
names cc99xx and iissoo99889999::119999xx are deprecated.
-
ggnnuu8899
Default, ISO C90 plus GNU extensions (including some C99 features).
-
-
ggnnuu9999
-
-
ggnnuu99xx
ISO C99 plus GNU extensions. When ISO C99 is fully implemented in GCC,
-
this will become the default. The name ggnnuu99xx is deprecated.
-
cc++++9988
The 1998 ISO C++ standard plus amendments.
-
-
ggnnuu++++9988
The same as --ssttdd==cc++++9988 plus GNU extensions. This is the
-
default for C++ code.
Even when this option is not specified, you can still use some of the
features of newer standards in so far as they do not conflict with
previous C standards. For example, you may use "__restrict__" even
when --ssttdd==cc9999 is not specified.
The --ssttdd options specifying some version of ISO C have the same
effects as --aannssii, except that features that were not in ISO C90
but are in the specified version (for example, //// comments and
the "inline" keyword in ISO C99) are not disabled.
-
--aauuxx--iinnffoo _f_i_l_e_n_a_m_e
Output to the given filename prototyped declarations for all functions
-
declared and/or defined in a translation unit, including those in header
files. This option is silently ignored in any language other than C.
Besides declarations, the file indicates, in comments, the origin of
each declaration (source file and line), whether the declaration was
implicit, prototyped or unprototyped (II, NN for new or
OO for old, respectively, in the first character after the line
number and the colon), and whether it came from a declaration or a
definition (CC or FF, respectively, in the following
character). In the case of function definitions, a K&R-style list of
arguments followed by their declarations is also provided, inside
comments, after the declaration.
-
--ffnnoo--aassmm
Do not recognize "asm", "inline" or "typeof" as a
-
keyword, so that code can use these words as identifiers. You can use
the keywords "__asm__", "__inline__" and "__typeof__"
instead. --aannssii implies --ffnnoo--aassmm.
In C++, this switch only affects the "typeof" keyword, since
"asm" and "inline" are standard keywords. You may want to
use the --ffnnoo--ggnnuu--kkeeyywwoorrddss flag instead, which has the same
effect. In C99 mode (--ssttdd==cc9999 or --ssttdd==ggnnuu9999), this
switch only affects the "asm" and "typeof" keywords, since
"inline" is a standard keyword in ISO C99.
-
--ffnnoo--bbuuiillttiinn
-
-
--ffnnoo--bbuuiillttiinn--_f_u_n_c_t_i_o_n
Don't recognize built-in functions that do not begin with
-
____bbuuiillttiinn__ as prefix.
GCC normally generates special code to handle certain built-in functions
more efficiently; for instance, calls to "alloca" may become single
instructions that adjust the stack directly, and calls to "memcpy"
may become inline copy loops. The resulting code is often both smaller
and faster, but since the function calls no longer appear as such, you
cannot set a breakpoint on those calls, nor can you change the behavior
of the functions by linking with a different library. In addition,
when a function is recognized as a built-in function, GCC may use
information about that function to warn about problems with calls to
that function, or to generate more efficient code, even if the
resulting code still contains calls to that function. For example,
warnings are given with --WWffoorrmmaatt for bad calls to
"printf", when "printf" is built in, and "strlen" is
known not to modify global memory.
With the --ffnnoo--bbuuiillttiinn--_f_u_n_c_t_i_o_n option
only the built-in function _f_u_n_c_t_i_o_n is
disabled. _f_u_n_c_t_i_o_n must not begin with ____bbuuiillttiinn__. If a
function is named this is not built-in in this version of GCC, this
option is ignored. There is no corresponding
--ffbbuuiillttiinn--_f_u_n_c_t_i_o_n option; if you wish to enable
built-in functions selectively when using --ffnnoo--bbuuiillttiinn or
--ffffrreeeessttaannddiinngg, you may define macros such as:
#define abs(n) __builtin_abs ((n))
#define strcpy(d, s) __builtin_strcpy ((d), (s))
-
--ffhhoosstteedd
Assert that compilation takes place in a hosted environment. This implies
-
--ffbbuuiillttiinn. A hosted environment is one in which the
entire standard library is available, and in which "main" has a return
type of "int". Examples are nearly everything except a kernel.
This is equivalent to --ffnnoo--ffrreeeessttaannddiinngg.
-
--ffffrreeeessttaannddiinngg
Assert that compilation takes place in a freestanding environment. This
-
implies --ffnnoo--bbuuiillttiinn. A freestanding environment
is one in which the standard library may not exist, and program startup may
not necessarily be at "main". The most obvious example is an OS kernel.
This is equivalent to --ffnnoo--hhoosstteedd.
-
--ffmmss--eexxtteennssiioonnss
Accept some non-standard constructs used in Microsoft header files.
-
Some cases of unnamed fields in structures and unions are only
accepted with this option.
-
--ttrriiggrraapphhss
Support ISO C trigraphs. The --aannssii option (and --ssttdd
-
options for strict ISO C conformance) implies --ttrriiggrraapphhss.
-
--nnoo--iinntteeggrraatteedd--ccpppp
Performs a compilation in two passes: preprocessing and compiling. This
-
option allows a user supplied "cc1", "cc1plus", or "cc1obj" via the
--BB option. The user supplied compilation step can then add in
an additional preprocessing step after normal preprocessing but before
compiling. The default is to use the integrated cpp (internal cpp)
The semantics of this option will change if "cc1", "cc1plus", and
"cc1obj" are merged.
-
--ttrraaddiittiioonnaall
-
-
--ttrraaddiittiioonnaall--ccpppp
Formerly, these options caused GCC to attempt to emulate a pre-standard
-
C compiler. They are now only supported with the --EE switch.
The preprocessor continues to support a pre-standard mode. See the GNU
CPP manual for details.
-
--ffccoonndd--mmiissmmaattcchh
Allow conditional expressions with mismatched types in the second and
-
third arguments. The value of such an expression is void. This option
is not supported for C++.
-
--ffuunnssiiggnneedd--cchhaarr
Let the type "char" be unsigned, like "unsigned char".
-
Each kind of machine has a default for what "char" should
be. It is either like "unsigned char" by default or like
"signed char" by default.
Ideally, a portable program should always use "signed char" or
"unsigned char" when it depends on the signedness of an object.
But many programs have been written to use plain "char" and
expect it to be signed, or expect it to be unsigned, depending on the
machines they were written for. This option, and its inverse, let you
make such a program work with the opposite default.
The type "char" is always a distinct type from each of
"signed char" or "unsigned char", even though its behavior
is always just like one of those two.
-
--ffssiiggnneedd--cchhaarr
Let the type "char" be signed, like "signed char".
-
Note that this is equivalent to --ffnnoo--uunnssiiggnneedd--cchhaarr, which is
the negative form of --ffuunnssiiggnneedd--cchhaarr. Likewise, the option
--ffnnoo--ssiiggnneedd--cchhaarr is equivalent to --ffuunnssiiggnneedd--cchhaarr.
-
--ffssiiggnneedd--bbiittffiieellddss
-
-
--ffuunnssiiggnneedd--bbiittffiieellddss
-
-
--ffnnoo--ssiiggnneedd--bbiittffiieellddss
-
-
--ffnnoo--uunnssiiggnneedd--bbiittffiieellddss
These options control whether a bit-field is signed or unsigned, when the
-
declaration does not use either "signed" or "unsigned". By
default, such a bit-field is signed, because this is consistent: the
basic integer types such as "int" are signed types.
OOppttiioonnss CCoonnttrroolllliinngg CC++++ DDiiaalleecctt
This section describes the command-line options that are only meaningful
for C++ programs; but you can also use most of the GNU compiler options
regardless of what language your program is in. For example, you
might compile a file "firstClass.C" like this:
g++ -g -frepo -O -c firstClass.C
In this example, only --ffrreeppoo is an option meant
only for C++ programs; you can use the other options with any
language supported by GCC.
Here is a list of options that are _o_n_l_y for compiling C++ programs:
-
--ffaabbii--vveerrssiioonn==_n
Use version _n of the C++ ABI. Version 2 is the version of the
-
C++ ABI that first appeared in G++ 3.4. Version 1 is the version of
the C++ ABI that first appeared in G++ 3.2. Version 0 will always be
the version that conforms most closely to the C++ ABI specification.
Therefore, the ABI obtained using version 0 will change as ABI bugs
are fixed.
The default is version 2.
-
--ffnnoo--aacccceessss--ccoonnttrrooll
Turn off all access checking. This switch is mainly useful for working
-
around bugs in the access control code.
-
--ffcchheecckk--nneeww
Check that the pointer returned by "operator new" is non-null
-
before attempting to modify the storage allocated. This check is
normally unnecessary because the C++ standard specifies that
"operator new" will only return 0 if it is declared
_tt_hh_rr_oo_ww_((_)), in which case the compiler will always check the
return value even without this option. In all other cases, when
"operator new" has a non-empty exception specification, memory
exhaustion is signalled by throwing "std::bad_alloc". See also
nneeww ((nnootthhrrooww)).
-
--ffccoonnsseerrvvee--ssppaaccee
Put uninitialized or runtime-initialized global variables into the
-
common segment, as C does. This saves space in the executable at the
cost of not diagnosing duplicate definitions. If you compile with this
flag and your program mysteriously crashes after "main()" has
completed, you may have an object that is being destroyed twice because
two definitions were merged.
This option is no longer useful on most targets, now that support has
been added for putting variables into BSS without making them common.
-
--ffffrriieenndd--iinnjjeeccttiioonn
Inject friend functions into the enclosing namespace, so that they are
-
visible outside the scope of the class in which they are declared.
Friend functions were documented to work this way in the old Annotated
C++ Reference Manual, and versions of G++ before 4.1 always worked
that way. However, in ISO C++ a friend function which is not declared
in an enclosing scope can only be found using argument dependent
lookup. This option causes friends to be injected as they were in
earlier releases.
This option is for compatibility, and may be removed in a future
release of G++.
-
--ffnnoo--ccoonnsstt--ssttrriinnggss
Give string constants type "char *" instead of type "const
-
char *". By default, G++ uses type "const char *" as required by
the standard. Even if you use --ffnnoo--ccoonnsstt--ssttrriinnggss, you cannot
actually modify the value of a string constant.
This option might be removed in a future release of G++. For maximum
portability, you should structure your code so that it works with
string constants that have type "const char *".
-
--ffnnoo--eelliiddee--ccoonnssttrruuccttoorrss
The C++ standard allows an implementation to omit creating a temporary
-
which is only used to initialize another object of the same type.
Specifying this option disables that optimization, and forces G++ to
call the copy constructor in all cases.
-
--ffnnoo--eennffoorrccee--eehh--ssppeeccss
Don't generate code to check for violation of exception specifications
-
at runtime. This option violates the C++ standard, but may be useful
for reducing code size in production builds, much like defining
NNDDEEBBUUGG. This does not give user code permission to throw
exceptions in violation of the exception specifications; the compiler
will still optimize based on the specifications, so throwing an
unexpected exception will result in undefined behavior.
-
--ffffoorr--ssccooppee
-
-
--ffnnoo--ffoorr--ssccooppee
If --ffffoorr--ssccooppee is specified, the scope of variables declared in
-
a _f_o_r_-_i_n_i_t_-_s_t_a_t_e_m_e_n_t is limited to the ffoorr loop itself,
as specified by the C++ standard.
If --ffnnoo--ffoorr--ssccooppee is specified, the scope of variables declared in
a _f_o_r_-_i_n_i_t_-_s_t_a_t_e_m_e_n_t extends to the end of the enclosing scope,
as was the case in old versions of G++, and other (traditional)
implementations of C++.
The default if neither flag is given to follow the standard,
but to allow and give a warning for old-style code that would
otherwise be invalid, or have different behavior.
-
--ffnnoo--ggnnuu--kkeeyywwoorrddss
Do not recognize "typeof" as a keyword, so that code can use this
-
word as an identifier. You can use the keyword "__typeof__" instead.
--aannssii implies --ffnnoo--ggnnuu--kkeeyywwoorrddss.
-
--ffnnoo--iimmpplliicciitt--tteemmppllaatteess
Never emit code for non-inline templates which are instantiated
-
implicitly (i.e. by use); only emit code for explicit instantiations.
-
--ffnnoo--iimmpplliicciitt--iinnlliinnee--tteemmppllaatteess
Don't emit code for implicit instantiations of inline templates, either.
-
The default is to handle inlines differently so that compiles with and
without optimization will need the same set of explicit instantiations.
-
--ffnnoo--iimmpplleemmeenntt--iinnlliinneess
To save space, do not emit out-of-line copies of inline functions
-
controlled by ##pprraaggmmaa iimmpplleemmeennttaattiioonn. This will cause linker
errors if these functions are not inlined everywhere they are called.
-
--ffmmss--eexxtteennssiioonnss
Disable pedantic warnings about constructs used in MFC, such as implicit
-
int and getting a pointer to member function via non-standard syntax.
-
--ffnnoo--nnoonnaannssii--bbuuiillttiinnss
Disable built-in declarations of functions that are not mandated by
-
ANSI/ISO C. These include "ffs", "alloca", "_exit",
"index", "bzero", "conjf", and other related functions.
-
--ffnnoo--ooppeerraattoorr--nnaammeess
Do not treat the operator name keywords "and", "bitand",
-
"bitor", "compl", "not", "or" and "xor" as
synonyms as keywords.
-
--ffnnoo--ooppttiioonnaall--ddiiaaggss
Disable diagnostics that the standard says a compiler does not need to
-
issue. Currently, the only such diagnostic issued by G++ is the one for
a name having multiple meanings within a class.
-
--ffppeerrmmiissssiivvee
Downgrade some diagnostics about nonconformant code from errors to
-
warnings. Thus, using --ffppeerrmmiissssiivvee will allow some
nonconforming code to compile.
-
--ffrreeppoo
Enable automatic template instantiation at link time. This option also
-
implies --ffnnoo--iimmpplliicciitt--tteemmppllaatteess.
-
--ffnnoo--rrttttii
Disable generation of information about every class with virtual
-
functions for use by the C++ runtime type identification features
(ddyynnaammiicc__ccaasstt and ttyyppeeiidd). If you don't use those parts
of the language, you can save some space by using this flag. Note that
exception handling uses the same information, but it will generate it as
needed.
-
--ffssttaattss
Emit statistics about front-end processing at the end of the compilation.
-
This information is generally only useful to the G++ development team.
-
--fftteemmppllaattee--ddeepptthh--_n
Set the maximum instantiation depth for template classes to _n.
-
A limit on the template instantiation depth is needed to detect
endless recursions during template class instantiation. ANSI/ISO C++
conforming programs must not rely on a maximum depth greater than 17.
-
--ffnnoo--tthhrreeaaddssaaffee--ssttaattiiccss
Do not emit the extra code to use the routines specified in the C++
-
ABI for thread-safe initialization of local statics. You can use this
option to reduce code size slightly in code that doesn't need to be
thread-safe.
-
--ffuussee--ccxxaa--aatteexxiitt
Register destructors for objects with static storage duration with the
-
"__cxa_atexit" function rather than the "atexit" function.
This option is required for fully standards-compliant handling of static
destructors, but will only work if your C library supports
"__cxa_atexit".
-
--ffvviissiibbiilliittyy--iinnlliinneess--hhiiddddeenn
Causes all inlined methods to be marked with
-
"__attribute__ ((visibility ("hidden")))" so that they do not
appear in the export table of a DSO and do not require a PLT indirection
when used within the DSO. Enabling this option can have a dramatic effect
on load and link times of a DSO as it massively reduces the size of the
dynamic export table when the library makes heavy use of templates. While
it can cause bloating through duplication of code within each DSO where
it is used, often the wastage is less than the considerable space occupied
by a long symbol name in the export table which is typical when using
templates and namespaces. For even more savings, combine with the
--ffvviissiibbiilliittyy==hhiiddddeenn switch.
-
--ffnnoo--wweeaakk
Do not use weak symbol support, even if it is provided by the linker.
-
By default, G++ will use weak symbols if they are available. This
option exists only for testing, and should not be used by end-users;
it will result in inferior code and has no benefits. This option may
be removed in a future release of G++.
-
--nnoossttddiinncc++++
Do not search for header files in the standard directories specific to
-
C++, but do still search the other standard directories. (This option
is used when building the C++ library.)
In addition, these optimization, warning, and code generation options
have meanings only for C++ programs:
-
--ffnnoo--ddeeffaauulltt--iinnlliinnee
Do not assume iinnlliinnee for functions defined inside a class scope.
-
Note that these
functions will have linkage like inline functions; they just won't be
inlined by default.
-
--WWaabbii (C++ only)
Warn when G++ generates code that is probably not compatible with the
-
vendor-neutral C++ ABI. Although an effort has been made to warn about
all such cases, there are probably some cases that are not warned about,
even though G++ is generating incompatible code. There may also be
cases where warnings are emitted even though the code that is generated
will be compatible.
You should rewrite your code to avoid these warnings if you are
concerned about the fact that code generated by G++ may not be binary
compatible with code generated by other compilers.
The known incompatibilities at this point include:
-
*
Incorrect handling of tail-padding for bit-fields. G++ may attempt to
-
pack data into the same byte as a base class. For example:
struct A { virtual void f(); int f1 : 1; };
struct B : public A { int f2 : 1; };
In this case, G++ will place "B::f2" into the same byte
as"A::f1"; other compilers will not. You can avoid this problem
by explicitly padding "A" so that its size is a multiple of the
byte size on your platform; that will cause G++ and other compilers to
layout "B" identically.
-
*
Incorrect handling of tail-padding for virtual bases. G++ does not use
-
tail padding when laying out virtual bases. For example:
struct A { virtual void f(); char c1; };
struct B { B(); char c2; };
struct C : public A, public virtual B {};
In this case, G++ will not place "B" into the tail-padding for
"A"; other compilers will. You can avoid this problem by
explicitly padding "A" so that its size is a multiple of its
alignment (ignoring virtual base classes); that will cause G++ and other
compilers to layout "C" identically.
-
*
Incorrect handling of bit-fields with declared widths greater than that
-
of their underlying types, when the bit-fields appear in a union. For
example:
union U { int i : 4096; };
Assuming that an "int" does not have 4096 bits, G++ will make the
union too small by the number of bits in an "int".
-
*
Empty classes can be placed at incorrect offsets. For example:
-
struct A {};
struct B {
A a;
virtual void f ();
};
struct C : public B, public A {};
G++ will place the "A" base class of "C" at a nonzero offset;
it should be placed at offset zero. G++ mistakenly believes that the
"A" data member of "B" is already at offset zero.
-
*
Names of template functions whose types involve "typename" or
-
template template parameters can be mangled incorrectly.
template
void f(typename Q::X) {}
template class Q>
void f(typename Q::X) {}
Instantiations of these templates may be mangled incorrectly.
-
--WWccttoorr--ddttoorr--pprriivvaaccyy (C++ only)
Warn when a class seems unusable because all the constructors or
-
destructors in that class are private, and it has neither friends nor
public static member functions.
-
--WWnnoonn--vviirrttuuaall--ddttoorr (C++ only)
Warn when a class appears to be polymorphic, thereby requiring a virtual
-
destructor, yet it declares a non-virtual one.
This warning is enabled by --WWaallll.
-
--WWrreeoorrddeerr (C++ only)
Warn when the order of member initializers given in the code does not
-
match the order in which they must be executed. For instance:
struct A {
int i;
int j;
A(): j (0), i (1) { }
};
The compiler will rearrange the member initializers for ii
and jj to match the declaration order of the members, emitting
a warning to that effect. This warning is enabled by --WWaallll.
The following --WW...... options are not affected by --WWaallll.
-
--WWeeffffcc++++ (C++ only)
Warn about violations of the following style guidelines from Scott Meyers'
-
_E_f_f_e_c_t_i_v_e _C_+_+ book:
-
*
Item 11: Define a copy constructor and an assignment operator for classes
-
with dynamically allocated memory.
-
*
Item 12: Prefer initialization to assignment in constructors.
-
-
*
Item 14: Make destructors virtual in base classes.
-
-
*
Item 15: Have "operator=" return a reference to *this.
-
-
*
Item 23: Don't try to return a reference when you must return an object.
-
Also warn about violations of the following style guidelines from
Scott Meyers' _M_o_r_e _E_f_f_e_c_t_i_v_e _C_+_+ book:
-
*
Item 6: Distinguish between prefix and postfix forms of increment and
-
decrement operators.
-
*
Item 7: Never overload "&&", "||", or ",".
-
When selecting this option, be aware that the standard library
headers do not obey all of these guidelines; use ggrreepp --vv
to filter out those warnings.
-
--WWnnoo--ddeepprreeccaatteedd (C++ only)
Do not warn about usage of deprecated features.
-
-
--WWssttrriicctt--nnuullll--sseennttiinneell (C++ only)
Warn also about the use of an uncasted "NULL" as sentinel. When
-
compiling only with GCC this is a valid sentinel, as "NULL" is defined
to "__null". Although it is a null pointer constant not a null pointer,
it is guaranteed to of the same size as a pointer. But this use is
not portable across different compilers.
-
--WWnnoo--nnoonn--tteemmppllaattee--ffrriieenndd (C++ only)
Disable warnings when non-templatized friend functions are declared
-
within a template. Since the advent of explicit template specification
support in G++, if the name of the friend is an unqualified-id (i.e.,
ffrriieenndd ffoooo((iinntt))), the C++ language specification demands that the
friend declare or define an ordinary, nontemplate function. (Section
14.5.3). Before G++ implemented explicit specification, unqualified-ids
could be interpreted as a particular specialization of a templatized
function. Because this non-conforming behavior is no longer the default
behavior for G++, --WWnnoonn--tteemmppllaattee--ffrriieenndd allows the compiler to
check existing code for potential trouble spots and is on by default.
This new compiler behavior can be turned off with
--WWnnoo--nnoonn--tteemmppllaattee--ffrriieenndd which keeps the conformant compiler code
but disables the helpful warning.
-
--WWoolldd--ssttyyllee--ccaasstt (C++ only)
Warn if an old-style (C-style) cast to a non-void type is used within
-
a C++ program. The new-style casts (ddyynnaammiicc__ccaasstt,
ssttaattiicc__ccaasstt, rreeiinntteerrpprreett__ccaasstt, and ccoonnsstt__ccaasstt) are
less vulnerable to unintended effects and much easier to search for.
-
--WWoovveerrllooaaddeedd--vviirrttuuaall (C++ only)
Warn when a function declaration hides virtual functions from a
-
base class. For example, in:
struct A {
virtual void f();
};
struct B: public A {
void f(int);
};
the "A" class version of "f" is hidden in "B", and code
like:
B* b;
b->f();
will fail to compile.
-
--WWnnoo--ppmmff--ccoonnvveerrssiioonnss (C++ only)
Disable the diagnostic for converting a bound pointer to member function
-
to a plain pointer.
-
--WWssiiggnn--pprroommoo (C++ only)
Warn when overload resolution chooses a promotion from unsigned or
-
enumerated type to a signed type, over a conversion to an unsigned type of
the same size. Previous versions of G++ would try to preserve
unsignedness, but the standard mandates the current behavior.
struct A {
operator int ();
A& operator = (int);
};
main ()
{
A a,b;
a = b;
}
In this example, G++ will synthesize a default AA&& ooppeerraattoorr ==
((ccoonnsstt AA&&));;, while cfront will use the user-defined ooppeerraattoorr ==.
OOppttiioonnss CCoonnttrroolllliinngg OObbjjeeccttiivvee--CC aanndd OObbjjeeccttiivvee--CC++++ DDiiaalleeccttss
(NOTE: This manual does not describe the Objective-C and Objective-C++
languages themselves. See
This section describes the command-line options that are only meaningful
for Objective-C and Objective-C++ programs, but you can also use most of
the language-independent GNU compiler options.
For example, you might compile a file "some_class.m" like this:
gcc -g -fgnu-runtime -O -c some_class.m
In this example, --ffggnnuu--rruunnttiimmee is an option meant only for
Objective-C and Objective-C++ programs; you can use the other options with
any language supported by GCC.
Note that since Objective-C is an extension of the C language, Objective-C
compilations may also use options specific to the C front-end (e.g.,
--WWttrraaddiittiioonnaall). Similarly, Objective-C++ compilations may use
C++-specific options (e.g., --WWaabbii).
Here is a list of options that are _o_n_l_y for compiling Objective-C
and Objective-C++ programs:
-
--ffccoonnssttaanntt--ssttrriinngg--ccllaassss==_c_l_a_s_s_-_n_a_m_e
Use _c_l_a_s_s_-_n_a_m_e as the name of the class to instantiate for each
-
literal string specified with the syntax "@"..."". The default
class name is "NXConstantString" if the GNU runtime is being used, and
"NSConstantString" if the NeXT runtime is being used (see below). The
--ffccoonnssttaanntt--ccffssttrriinnggss option, if also present, will override the
--ffccoonnssttaanntt--ssttrriinngg--ccllaassss setting and cause "@"..."" literals
to be laid out as constant CoreFoundation strings.
-
--ffggnnuu--rruunnttiimmee
Generate object code compatible with the standard GNU Objective-C
-
runtime. This is the default for most types of systems.
-
--ffnneexxtt--rruunnttiimmee
Generate output compatible with the NeXT runtime. This is the default
-
for NeXT-based systems, including Darwin and Mac OS X. The macro
"__NEXT_RUNTIME__" is predefined if (and only if) this option is
used.
-
--ffnnoo--nniill--rreecceeiivveerrss
Assume that all Objective-C message dispatches (e.g.,
-
"[receiver message:arg]") in this translation unit ensure that the receiver
is not "nil". This allows for more efficient entry points in the runtime
to be used. Currently, this option is only available in conjunction with
the NeXT runtime on Mac OS X 10.3 and later.
-
--ffoobbjjcc--ccaallll--ccxxxx--ccddttoorrss
For each Objective-C class, check if any of its instance variables is a
-
C++ object with a non-trivial default constructor. If so, synthesize a
special "- (id) .cxx_construct" instance method that will run
non-trivial default constructors on any such instance variables, in order,
and then return "self". Similarly, check if any instance variable
is a C++ object with a non-trivial destructor, and if so, synthesize a
special "- (void) .cxx_destruct" method that will run
all such default destructors, in reverse order.
The "- (id) .cxx_construct" and/or "- (void) .cxx_destruct" methods
thusly generated will only operate on instance variables declared in the
current Objective-C class, and not those inherited from superclasses. It
is the responsibility of the Objective-C runtime to invoke all such methods
in an object's inheritance hierarchy. The "- (id) .cxx_construct" methods
will be invoked by the runtime immediately after a new object
instance is allocated; the "- (void) .cxx_destruct" methods will
be invoked immediately before the runtime deallocates an object instance.
As of this writing, only the NeXT runtime on Mac OS X 10.4 and later has
support for invoking the "- (id) .cxx_construct" and
"- (void) .cxx_destruct" methods.
-
--ffoobbjjcc--ddiirreecctt--ddiissppaattcchh
Allow fast jumps to the message dispatcher. On Darwin this is
-
accomplished via the comm page.
-
--ffoobbjjcc--eexxcceeppttiioonnss
Enable syntactic support for structured exception handling in Objective-C,
-
similar to what is offered by C++ and Java. Currently, this option is only
available in conjunction with the NeXT runtime on Mac OS X 10.3 and later.
@try {
...
@throw expr;
...
}
@catch (AnObjCClass *exc) {
...
@throw expr;
...
@throw;
...
}
@catch (AnotherClass *exc) {
...
}
@catch (id allOthers) {
...
}
@finally {
...
@throw expr;
...
}
The @throw statement may appear anywhere in an Objective-C or
Objective-C++ program; when used inside of a @catch block, the
@throw may appear without an argument (as shown above), in which case
the object caught by the @catch will be rethrown.
Note that only (pointers to) Objective-C objects may be thrown and
caught using this scheme. When an object is thrown, it will be caught
by the nearest @catch clause capable of handling objects of that type,
analogously to how "catch" blocks work in C++ and Java. A
"@catch(id ...)" clause (as shown above) may also be provided to catch
any and all Objective-C exceptions not caught by previous @catch
clauses (if any).
The @finally clause, if present, will be executed upon exit from the
immediately preceding "@try ... @catch" section. This will happen
regardless of whether any exceptions are thrown, caught or rethrown
inside the "@try ... @catch" section, analogously to the behavior
of the "finally" clause in Java.
There are several caveats to using the new exception mechanism:
-
*
Although currently designed to be binary compatible with "NS_HANDLER"-style
-
idioms provided by the "NSException" class, the new
exceptions can only be used on Mac OS X 10.3 (Panther) and later
systems, due to additional functionality needed in the (NeXT) Objective-C
runtime.
-
*
As mentioned above, the new exceptions do not support handling
-
types other than Objective-C objects. Furthermore, when used from
Objective-C++, the Objective-C exception model does not interoperate with C++
exceptions at this time. This means you cannot @throw an exception
from Objective-C and "catch" it in C++, or vice versa
(i.e., "throw ... @catch").
The --ffoobbjjcc--eexxcceeppttiioonnss switch also enables the use of synchronization
blocks for thread-safe execution:
@synchronized (ObjCClass *guard) {
...
}
Upon entering the @synchronized block, a thread of execution shall
first check whether a lock has been placed on the corresponding "guard"
object by another thread. If it has, the current thread shall wait until
the other thread relinquishes its lock. Once "guard" becomes available,
the current thread will place its own lock on it, execute the code contained in
the @synchronized block, and finally relinquish the lock (thereby
making "guard" available to other threads).
Unlike Java, Objective-C does not allow for entire methods to be marked
@synchronized. Note that throwing exceptions out of
@synchronized blocks is allowed, and will cause the guarding object
to be unlocked properly.
-
--ffoobbjjcc--ggcc
Enable garbage collection (GC) in Objective-C and Objective-C++ programs.
-
-
--ffrreeppllaaccee--oobbjjcc--ccllaasssseess
Emit a special marker instructing _ll_dd((11)) not to statically link in
-
the resulting object file, and allow _dd_yy_ll_dd((11)) to load it in at
run time instead. This is used in conjunction with the Fix-and-Continue
debugging mode, where the object file in question may be recompiled and
dynamically reloaded in the course of program execution, without the need
to restart the program itself. Currently, Fix-and-Continue functionality
is only available in conjunction with the NeXT runtime on Mac OS X 10.3
and later.
-
--ffzzeerroo--lliinnkk
When compiling for the NeXT runtime, the compiler ordinarily replaces calls
-
to "objc_getClass("...")" (when the name of the class is known at
compile time) with static class references that get initialized at load time,
which improves run-time performance. Specifying the --ffzzeerroo--lliinnkk flag
suppresses this behavior and causes calls to "objc_getClass("...")"
to be retained. This is useful in Zero-Link debugging mode, since it allows
for individual class implementations to be modified during program execution.
-
--ggeenn--ddeeccllss
Dump interface declarations for all classes seen in the source file to a
-
file named _s_o_u_r_c_e_n_a_m_e_._d_e_c_l.
-
--WWaassssiiggnn--iinntteerrcceepptt
Warn whenever an Objective-C assignment is being intercepted by the
-
garbage collector.
-
--WWnnoo--pprroottooccooll
If a class is declared to implement a protocol, a warning is issued for
-
every method in the protocol that is not implemented by the class. The
default behavior is to issue a warning for every method not explicitly
implemented in the class, even if a method implementation is inherited
from the superclass. If you use the --WWnnoo--pprroottooccooll option, then
methods inherited from the superclass are considered to be implemented,
and no warning is issued for them.
-
--WWsseelleeccttoorr
Warn if multiple methods of different types for the same selector are
-
found during compilation. The check is performed on the list of methods
in the final stage of compilation. Additionally, a check is performed
for each selector appearing in a "@selector(...)"
expression, and a corresponding method for that selector has been found
during compilation. Because these checks scan the method table only at
the end of compilation, these warnings are not produced if the final
stage of compilation is not reached, for example because an error is
found during compilation, or because the --ffssyynnttaaxx--oonnllyy option is
being used.
-
--WWssttrriicctt--sseelleeccttoorr--mmaattcchh
Warn if multiple methods with differing argument and/or return types are
-
found for a given selector when attempting to send a message using this
selector to a receiver of type "id" or "Class". When this flag
is off (which is the default behavior), the compiler will omit such warnings
if any differences found are confined to types which share the same size
and alignment.
-
--WWuunnddeeccllaarreedd--sseelleeccttoorr
Warn if a "@selector(...)" expression referring to an
-
undeclared selector is found. A selector is considered undeclared if no
method with that name has been declared before the
"@selector(...)" expression, either explicitly in an
@interface or @protocol declaration, or implicitly in
an @implementation section. This option always performs its
checks as soon as a "@selector(...)" expression is found,
while --WWsseelleeccttoorr only performs its checks in the final stage of
compilation. This also enforces the coding style convention
that methods and selectors must be declared before being used.
-
--pprriinntt--oobbjjcc--rruunnttiimmee--iinnffoo
Generate C header describing the largest structure that is passed by
-
value, if any.
OOppttiioonnss ttoo CCoonnttrrooll DDiiaaggnnoossttiicc MMeessssaaggeess FFoorrmmaattttiinngg
Traditionally, diagnostic messages have been formatted irrespective of
the output device's aspect (e.g. its width, ...). The options described
below can be used to control the diagnostic messages formatting
algorithm, e.g. how many characters per line, how often source location
information should be reported. Right now, only the C++ front end can
honor these options. However it is expected, in the near future, that
the remaining front ends would be able to digest them correctly.
-
--ffmmeessssaaggee--lleennggtthh==_n
Try to format error messages so that they fit on lines of about _n
-
characters. The default is 72 characters for gg++++ and 0 for the rest of
the front ends supported by GCC. If _n is zero, then no
line-wrapping will be done; each error message will appear on a single
line.
-
--ffddiiaaggnnoossttiiccss--sshhooww--llooccaattiioonn==oonnccee
Only meaningful in line-wrapping mode. Instructs the diagnostic messages
-
reporter to emit _o_n_c_e source location information; that is, in
case the message is too long to fit on a single physical line and has to
be wrapped, the source location won't be emitted (as prefix) again,
over and over, in subsequent continuation lines. This is the default
behavior.
-
--ffddiiaaggnnoossttiiccss--sshhooww--llooccaattiioonn==eevveerryy--lliinnee
Only meaningful in line-wrapping mode. Instructs the diagnostic
-
messages reporter to emit the same source location information (as
prefix) for physical lines that result from the process of breaking
a message which is too long to fit on a single line.
-
--ffddiiaaggnnoossttiiccss--sshhooww--ooppttiioonnss
This option instructs the diagnostic machinery to add text to each
-
diagnostic emitted, which indicates which command line option directly
controls that diagnostic, when such an option is known to the
diagnostic machinery.
OOppttiioonnss ttoo RReeqquueesstt oorr SSuupppprreessss WWaarrnniinnggss
Warnings are diagnostic messages that report constructions which
are not inherently erroneous but which are risky or suggest there
may have been an error.
You can request many specific warnings with options beginning --WW,
for example --WWiimmpplliicciitt to request warnings on implicit
declarations. Each of these specific warning options also has a
negative form beginning --WWnnoo-- to turn off warnings;
for example, --WWnnoo--iimmpplliicciitt. This manual lists only one of the
two forms, whichever is not the default.
The following options control the amount and kinds of warnings produced
by GCC; for further, language-specific options also refer to
CC++++ DDiiaalleecctt OOppttiioonnss and OObbjjeeccttiivvee--CC aanndd OObbjjeeccttiivvee--CC++++ DDiiaalleecctt
OOppttiioonnss.
-
--ffssyynnttaaxx--oonnllyy
Check the code for syntax errors, but don't do anything beyond that.
-
-
--ppeeddaannttiicc
Issue all the warnings demanded by strict ISO C and ISO C++;
-
reject all programs that use forbidden extensions, and some other
programs that do not follow ISO C and ISO C++. For ISO C, follows the
version of the ISO C standard specified by any --ssttdd option used.
Valid ISO C and ISO C++ programs should compile properly with or without
this option (though a rare few will require --aannssii or a
--ssttdd option specifying the required version of ISO C). However,
without this option, certain GNU extensions and traditional C and C++
features are supported as well. With this option, they are rejected.
--ppeeddaannttiicc does not cause warning messages for use of the
alternate keywords whose names begin and end with ____. Pedantic
warnings are also disabled in the expression that follows
"__extension__". However, only system header files should use
these escape routes; application programs should avoid them.
Some users try to use --ppeeddaannttiicc to check programs for strict ISO
C conformance. They soon find that it does not do quite what they want:
it finds some non-ISO practices, but not all---only those for which
ISO C _r_e_q_u_i_r_e_s a diagnostic, and some others for which
diagnostics have been added.
A feature to report any failure to conform to ISO C might be useful in
some instances, but would require considerable additional work and would
be quite different from --ppeeddaannttiicc. We don't have plans to
support such a feature in the near future.
Where the standard specified with --ssttdd represents a GNU
extended dialect of C, such as ggnnuu8899 or ggnnuu9999, there is a
corresponding _b_a_s_e _s_t_a_n_d_a_r_d, the version of ISO C on which the GNU
extended dialect is based. Warnings from --ppeeddaannttiicc are given
where they are required by the base standard. (It would not make sense
for such warnings to be given only for features not in the specified GNU
C dialect, since by definition the GNU dialects of C include all
features the compiler supports with the given option, and there would be
nothing to warn about.)
-
--ppeeddaannttiicc--eerrrroorrss
Like --ppeeddaannttiicc, except that errors are produced rather than
-
warnings.
-
--ww
Inhibit all warning messages.
-
-
--WWnnoo--iimmppoorrtt
Inhibit warning messages about the use of ##iimmppoorrtt.
-
-
--WWcchhaarr--ssuubbssccrriippttss
Warn if an array subscript has type "char". This is a common cause
-
of error, as programmers often forget that this type is signed on some
machines.
This warning is enabled by --WWaallll.
-
--WWccoommmmeenntt
Warn whenever a comment-start sequence //** appears in a //**
-
comment, or whenever a Backslash-Newline appears in a //// comment.
This warning is enabled by --WWaallll.
-
--WWffaattaall--eerrrroorrss
This option causes the compiler to abort compilation on the first error
-
occurred rather than trying to keep going and printing further error
messages.
-
--WWffoorrmmaatt
Check calls to "printf" and "scanf", etc., to make sure that
-
the arguments supplied have types appropriate to the format string
specified, and that the conversions specified in the format string make
sense. This includes standard functions, and others specified by format
attributes, in the "printf",
"scanf", "strftime" and "strfmon" (an X/Open extension,
not in the C standard) families (or other target-specific families).
Which functions are checked without format attributes having been
specified depends on the standard version selected, and such checks of
functions without the attribute specified are disabled by
--ffffrreeeessttaannddiinngg or --ffnnoo--bbuuiillttiinn.
The formats are checked against the format features supported by GNU
libc version 2.2. These include all ISO C90 and C99 features, as well
as features from the Single Unix Specification and some BSD and GNU
extensions. Other library implementations may not support all these
features; GCC does not support warning about features that go beyond a
particular library's limitations. However, if --ppeeddaannttiicc is used
with --WWffoorrmmaatt, warnings will be given about format features not
in the selected standard version (but not for "strfmon" formats,
since those are not in any version of the C standard).
Since --WWffoorrmmaatt also checks for null format arguments for
several functions, --WWffoorrmmaatt also implies --WWnnoonnnnuullll.
--WWffoorrmmaatt is included in --WWaallll. For more control over some
aspects of format checking, the options --WWffoorrmmaatt--yy22kk,
--WWnnoo--ffoorrmmaatt--eexxttrraa--aarrggss, --WWnnoo--ffoorrmmaatt--zzeerroo--lleennggtthh,
--WWffoorrmmaatt--nnoonnlliitteerraall, --WWffoorrmmaatt--sseeccuurriittyy, and
--WWffoorrmmaatt==22 are available, but are not included in --WWaallll.
-
--WWffoorrmmaatt--yy22kk
If --WWffoorrmmaatt is specified, also warn about "strftime"
-
formats which may yield only a two-digit year.
-
--WWnnoo--ffoorrmmaatt--eexxttrraa--aarrggss
If --WWffoorrmmaatt is specified, do not warn about excess arguments to a
-
"printf" or "scanf" format function. The C standard specifies
that such arguments are ignored.
Where the unused arguments lie between used arguments that are
specified with $$ operand number specifications, normally
warnings are still given, since the implementation could not know what
type to pass to "va_arg" to skip the unused arguments. However,
in the case of "scanf" formats, this option will suppress the
warning if the unused arguments are all pointers, since the Single
Unix Specification says that such unused arguments are allowed.
-
--WWnnoo--ffoorrmmaatt--zzeerroo--lleennggtthh
If --WWffoorrmmaatt is specified, do not warn about zero-length formats.
-
The C standard specifies that zero-length formats are allowed.
-
--WWffoorrmmaatt--nnoonnlliitteerraall
If --WWffoorrmmaatt is specified, also warn if the format string is not a
-
string literal and so cannot be checked, unless the format function
takes its format arguments as a "va_list".
-
--WWffoorrmmaatt--sseeccuurriittyy
If --WWffoorrmmaatt is specified, also warn about uses of format
-
functions that represent possible security problems. At present, this
warns about calls to "printf" and "scanf" functions where the
format string is not a string literal and there are no format arguments,
as in "printf (foo);". This may be a security hole if the format
string came from untrusted input and contains %%nn. (This is
currently a subset of what --WWffoorrmmaatt--nnoonnlliitteerraall warns about, but
in future warnings may be added to --WWffoorrmmaatt--sseeccuurriittyy that are not
included in --WWffoorrmmaatt--nnoonnlliitteerraall.)
-
--WWffoorrmmaatt==22
Enable --WWffoorrmmaatt plus format checks not included in
-
--WWffoorrmmaatt. Currently equivalent to --WWffoorrmmaatt
--WWffoorrmmaatt--nnoonnlliitteerraall --WWffoorrmmaatt--sseeccuurriittyy --WWffoorrmmaatt--yy22kk.
-
--WWnnoonnnnuullll
Warn about passing a null pointer for arguments marked as
-
requiring a non-null value by the "nonnull" function attribute.
--WWnnoonnnnuullll is included in --WWaallll and --WWffoorrmmaatt. It
can be disabled with the --WWnnoo--nnoonnnnuullll option.
-
--WWiinniitt--sseellff (C, C++, Objective-C and Objective-C++ only)
Warn about uninitialized variables which are initialized with themselves.
-
Note this option can only be used with the --WWuunniinniittiiaalliizzeedd option,
which in turn only works with --OO11 and above.
For example, GCC will warn about "i" being uninitialized in the
following snippet only when --WWiinniitt--sseellff has been specified:
int f()
{
int i = i;
return i;
}
-
--WWiimmpplliicciitt--iinntt
Warn when a declaration does not specify a type.
-
This warning is enabled by --WWaallll.
-
--WWiimmpplliicciitt--ffuunnccttiioonn--ddeeccllaarraattiioonn
-
-
--WWeerrrroorr--iimmpplliicciitt--ffuunnccttiioonn--ddeeccllaarraattiioonn
Give a warning (or error) whenever a function is used before being
-
declared. The form --WWnnoo--eerrrroorr--iimmpplliicciitt--ffuunnccttiioonn--ddeeccllaarraattiioonn
is not supported.
This warning is enabled by --WWaallll (as a warning, not an error).
-
--WWiimmpplliicciitt
Same as --WWiimmpplliicciitt--iinntt and --WWiimmpplliicciitt--ffuunnccttiioonn--ddeeccllaarraattiioonn.
-
This warning is enabled by --WWaallll.
-
--WWmmaaiinn
Warn if the type of mmaaiinn is suspicious. mmaaiinn should be a
-
function with external linkage, returning int, taking either zero
arguments, two, or three arguments of appropriate types.
This warning is enabled by --WWaallll.
-
--WWmmiissssiinngg--bbrraacceess
Warn if an aggregate or union initializer is not fully bracketed. In
-
the following example, the initializer for aa is not fully
bracketed, but that for bb is fully bracketed.
int a[2][2] = { 0, 1, 2, 3 };
int b[2][2] = { { 0, 1 }, { 2, 3 } };
This warning is enabled by --WWaallll.
-
--WWmmiissssiinngg--iinncclluuddee--ddiirrss (C, C++, Objective-C and Objective-C++ only)
Warn if a user-supplied include directory does not exist.
-
-
--WWppaarreenntthheesseess
Warn if parentheses are omitted in certain contexts, such
-
as when there is an assignment in a context where a truth value
is expected, or when operators are nested whose precedence people
often get confused about. Only the warning for an assignment used as
a truth value is supported when compiling C++; the other warnings are
only supported when compiling C.
Also warn if a comparison like xx<<==yy<<==zz appears; this is
equivalent to ((xx<<==yy ?? 11 :: 00)) <<== zz, which is a different
interpretation from that of ordinary mathematical notation.
Also warn about constructions where there may be confusion to which
"if" statement an "else" branch belongs. Here is an example of
such a case:
{
if (a)
if (b)
foo ();
else
bar ();
}
In C, every "else" branch belongs to the innermost possible "if"
statement, which in this example is "if (b)". This is often not
what the programmer expected, as illustrated in the above example by
indentation the programmer chose. When there is the potential for this
confusion, GCC will issue a warning when this flag is specified.
To eliminate the warning, add explicit braces around the innermost
"if" statement so there is no way the "else" could belong to
the enclosing "if". The resulting code would look like this:
{
if (a)
{
if (b)
foo ();
else
bar ();
}
}
This warning is enabled by --WWaallll.
-
--WWsseeqquueennccee--ppooiinntt
Warn about code that may have undefined semantics because of violations
-
of sequence point rules in the C standard.
The C standard defines the order in which expressions in a C program are
evaluated in terms of _s_e_q_u_e_n_c_e _p_o_i_n_t_s, which represent a partial
ordering between the execution of parts of the program: those executed
before the sequence point, and those executed after it. These occur
after the evaluation of a full expression (one which is not part of a
larger expression), after the evaluation of the first operand of a
"&&", "||", "? :" or "," (comma) operator, before a
function is called (but after the evaluation of its arguments and the
expression denoting the called function), and in certain other places.
Other than as expressed by the sequence point rules, the order of
evaluation of subexpressions of an expression is not specified. All
these rules describe only a partial order rather than a total order,
since, for example, if two functions are called within one expression
with no sequence point between them, the order in which the functions
are called is not specified. However, the standards committee have
ruled that function calls do not overlap.
It is not specified when between sequence points modifications to the
values of objects take effect. Programs whose behavior depends on this
have undefined behavior; the C standard specifies that "Between the
previous and next sequence point an object shall have its stored value
modified at most once by the evaluation of an expression. Furthermore,
the prior value shall be read only to determine the value to be
stored.". If a program breaks these rules, the results on any
particular implementation are entirely unpredictable.
Examples of code with undefined behavior are "a = a++;", "a[n]
= b[n++]" and "a[i++] = i;". Some more complicated cases are not
diagnosed by this option, and it may give an occasional false positive
result, but in general it has been found fairly effective at detecting
this sort of problem in programs.
The present implementation of this option only works for C programs. A
future implementation may also work for C++ programs.
The C standard is worded confusingly, therefore there is some debate
over the precise meaning of the sequence point rules in subtle cases.
Links to discussions of the problem, including proposed formal
definitions, may be found on the GCC readings page, at
.
This warning is enabled by --WWaallll.
-
--WWrreettuurrnn--ttyyppee
Warn whenever a function is defined with a return-type that defaults to
-
"int". Also warn about any "return" statement with no
return-value in a function whose return-type is not "void".
For C, also warn if the return type of a function has a type qualifier
such as "const". Such a type qualifier has no effect, since the
value returned by a function is not an lvalue. ISO C prohibits
qualified "void" return types on function definitions, so such
return types always receive a warning even without this option.
For C++, a function without return type always produces a diagnostic
message, even when --WWnnoo--rreettuurrnn--ttyyppee is specified. The only
exceptions are mmaaiinn and functions defined in system headers.
This warning is enabled by --WWaallll.
-
--WWsswwiittcchh
Warn whenever a "switch" statement has an index of enumerated type
-
and lacks a "case" for one or more of the named codes of that
enumeration. (The presence of a "default" label prevents this
warning.) "case" labels outside the enumeration range also
provoke warnings when this option is used.
This warning is enabled by --WWaallll.
-
--WWsswwiittcchh--ddeeffaauulltt
Warn whenever a "switch" statement does not have a "default"
-
case.
-
--WWsswwiittcchh--eennuumm
Warn whenever a "switch" statement has an index of enumerated type
-
and lacks a "case" for one or more of the named codes of that
enumeration. "case" labels outside the enumeration range also
provoke warnings when this option is used.
-
--WWttrriiggrraapphhss
Warn if any trigraphs are encountered that might change the meaning of
-
the program (trigraphs within comments are not warned about).
This warning is enabled by --WWaallll.
-
--WWuunnuusseedd--ffuunnccttiioonn
Warn whenever a static function is declared but not defined or a
-
non-inline static function is unused.
This warning is enabled by --WWaallll.
-
--WWuunnuusseedd--llaabbeell
Warn whenever a label is declared but not used.
-
This warning is enabled by --WWaallll.
To suppress this warning use the uunnuusseedd attribute.
-
--WWuunnuusseedd--ppaarraammeetteerr
Warn whenever a function parameter is unused aside from its declaration.
-
To suppress this warning use the uunnuusseedd attribute.
-
--WWuunnuusseedd--vvaarriiaabbllee
Warn whenever a local variable or non-constant static variable is unused
-
aside from its declaration
This warning is enabled by --WWaallll.
To suppress this warning use the uunnuusseedd attribute.
-
--WWuunnuusseedd--vvaalluuee
Warn whenever a statement computes a result that is explicitly not used.
-
This warning is enabled by --WWaallll.
To suppress this warning cast the expression to vvooiidd.
-
--WWuunnuusseedd
All the above --WWuunnuusseedd options combined.
-
In order to get a warning about an unused function parameter, you must
either specify --WWeexxttrraa --WWuunnuusseedd (note that --WWaallll implies
--WWuunnuusseedd), or separately specify --WWuunnuusseedd--ppaarraammeetteerr.
-
--WWuunniinniittiiaalliizzeedd
Warn if an automatic variable is used without first being initialized or
-
if a variable may be clobbered by a "setjmp" call.
These warnings are possible only in optimizing compilation,
because they require data flow information that is computed only
when optimizing. If you don't specify --OO, you simply won't
get these warnings.
If you want to warn about code which uses the uninitialized value of the
variable in its own initializer, use the --WWiinniitt--sseellff option.
These warnings occur for individual uninitialized or clobbered
elements of structure, union or array variables as well as for
variables which are uninitialized or clobbered as a whole. They do
not occur for variables or elements declared "volatile". Because
these warnings depend on optimization, the exact variables or elements
for which there are warnings will depend on the precise optimization
options and version of GCC used.
Note that there may be no warning about a variable that is used only
to compute a value that itself is never used, because such
computations may be deleted by data flow analysis before the warnings
are printed.
These warnings are made optional because GCC is not smart
enough to see all the reasons why the code might be correct
despite appearing to have an error. Here is one example of how
this can happen:
{
int x;
switch (y)
{
case 1: x = 1;
break;
case 2: x = 4;
break;
case 3: x = 5;
}
foo (x);
}
If the value of "y" is always 1, 2 or 3, then "x" is
always initialized, but GCC doesn't know this. Here is
another common case:
{
int save_y;
if (change_y) save_y = y, y = new_y;
...
if (change_y) y = save_y;
}
This has no bug because "save_y" is used only if it is set.
This option also warns when a non-volatile automatic variable might be
changed by a call to "longjmp". These warnings as well are possible
only in optimizing compilation.
The compiler sees only the calls to "setjmp". It cannot know
where "longjmp" will be called; in fact, a signal handler could
call it at any point in the code. As a result, you may get a warning
even when there is in fact no problem because "longjmp" cannot
in fact be called at the place which would cause a problem.
Some spurious warnings can be avoided if you declare all the functions
you use that never return as "noreturn".
This warning is enabled by --WWaallll.
-
--WWuunnkknnoowwnn--pprraaggmmaass
Warn when a #pragma directive is encountered which is not understood by
-
GCC. If this command line option is used, warnings will even be issued
for unknown pragmas in system header files. This is not the case if
the warnings were only enabled by the --WWaallll command line option.
-
--WWnnoo--pprraaggmmaass
Do not warn about misuses of pragmas, such as incorrect parameters,
-
invalid syntax, or conflicts between pragmas. See also
--WWuunnkknnoowwnn--pprraaggmmaass.
-
--WWssttrriicctt--aalliiaassiinngg
This option is only active when --ffssttrriicctt--aalliiaassiinngg is active.
-
It warns about code which might break the strict aliasing rules that the
compiler is using for optimization. The warning does not catch all
cases, but does attempt to catch the more common pitfalls. It is
included in --WWaallll.
-
--WWssttrriicctt--aalliiaassiinngg==22
This option is only active when --ffssttrriicctt--aalliiaassiinngg is active.
-
It warns about code which might break the strict aliasing rules that the
compiler is using for optimization. This warning catches more cases than
--WWssttrriicctt--aalliiaassiinngg, but it will also give a warning for some ambiguous
cases that are safe.
-
--WWaallll
All of the above --WW options combined. This enables all the
-
warnings about constructions that some users consider questionable, and
that are easy to avoid (or modify to prevent the warning), even in
conjunction with macros. This also enables some language-specific
warnings described in CC++++ DDiiaalleecctt OOppttiioonnss and
OObbjjeeccttiivvee--CC aanndd OObbjjeeccttiivvee--CC++++ DDiiaalleecctt OOppttiioonnss.
The following --WW...... options are not implied by --WWaallll.
Some of them warn about constructions that users generally do not
consider questionable, but which occasionally you might wish to check
for; others warn about constructions that are necessary or hard to avoid
in some cases, and there is no simple way to modify the code to suppress
the warning.
-
--WWeexxttrraa
(This option used to be called --WW. The older name is still
-
supported, but the newer name is more descriptive.) Print extra warning
messages for these events:
-
*
A function can return either with or without a value. (Falling
-
off the end of the function body is considered returning without
a value.) For example, this function would evoke such a
warning:
foo (a)
{
if (a > 0)
return a;
}
-
*
An expression-statement or the left-hand side of a comma expression
-
contains no side effects.
To suppress the warning, cast the unused expression to void.
For example, an expression such as xx[[ii,,jj]] will cause a warning,
but xx[[((vvooiidd))ii,,jj]] will not.
-
*
An unsigned value is compared against zero with << or >>==.
-
-
*
Storage-class specifiers like "static" are not the first things in
-
a declaration. According to the C Standard, this usage is obsolescent.
-
*
If --WWaallll or --WWuunnuusseedd is also specified, warn about unused
-
arguments.
-
*
A comparison between signed and unsigned values could produce an
-
incorrect result when the signed value is converted to unsigned.
(But don't warn if --WWnnoo--ssiiggnn--ccoommppaarree is also specified.)
-
*
An aggregate has an initializer which does not initialize all members.
-
This warning can be independently controlled by
--WWmmiissssiinngg--ffiieelldd--iinniittiiaalliizzeerrss.
-
*
A function parameter is declared without a type specifier in K&R-style
-
functions:
void foo(bar) { }
-
*
An empty body occurs in an iiff or eellssee statement.
-
-
*
A pointer is compared against integer zero with <<, <<==,
-
>>, or >>==.
-
*
A variable might be changed by lloonnggjjmmpp or vvffoorrkk.
-
-
*
Any of several floating-point events that often indicate errors, such as
-
overflow, underflow, loss of precision, etc.
-
*<(C++ only)>
An enumerator and a non-enumerator both appear in a conditional expression.
-
-
*<(C++ only)>
A non-static reference or non-static ccoonnsstt member appears in a
-
class without constructors.
-
*<(C++ only)>
Ambiguous virtual bases.
-
-
*<(C++ only)>
Subscripting an array which has been declared rreeggiisstteerr.
-
-
*<(C++ only)>
Taking the address of a variable which has been declared rreeggiisstteerr.
-
-
*<(C++ only)>
A base class is not initialized in a derived class' copy constructor.
-
-
--WWnnoo--ddiivv--bbyy--zzeerroo
Do not warn about compile-time integer division by zero. Floating point
-
division by zero is not warned about, as it can be a legitimate way of
obtaining infinities and NaNs.
-
--WWssyysstteemm--hheeaaddeerrss
Print warning messages for constructs found in system header files.
-
Warnings from system headers are normally suppressed, on the assumption
that they usually do not indicate real problems and would only make the
compiler output harder to read. Using this command line option tells
GCC to emit warnings from system headers as if they occurred in user
code. However, note that using --WWaallll in conjunction with this
option will _n_o_t warn about unknown pragmas in system
headers---for that, --WWuunnkknnoowwnn--pprraaggmmaass must also be used.
-
--WWffllooaatt--eeqquuaall
Warn if floating point values are used in equality comparisons.
-
The idea behind this is that sometimes it is convenient (for the
programmer) to consider floating-point values as approximations to
infinitely precise real numbers. If you are doing this, then you need
to compute (by analyzing the code, or in some other way) the maximum or
likely maximum error that the computation introduces, and allow for it
when performing comparisons (and when producing output, but that's a
different problem). In particular, instead of testing for equality, you
would check to see whether the two values have ranges that overlap; and
this is done with the relational operators, so equality comparisons are
probably mistaken.
-
--WWttrraaddiittiioonnaall (C only)
Warn about certain constructs that behave differently in traditional and
-
ISO C. Also warn about ISO C constructs that have no traditional C
equivalent, and/or problematic constructs which should be avoided.
-
*
Macro parameters that appear within string literals in the macro body.
-
In traditional C macro replacement takes place within string literals,
but does not in ISO C.
-
*
In traditional C, some preprocessor directives did not exist.
-
Traditional preprocessors would only consider a line to be a directive
if the ## appeared in column 1 on the line. Therefore
--WWttrraaddiittiioonnaall warns about directives that traditional C
understands but would ignore because the ## does not appear as the
first character on the line. It also suggests you hide directives like
##pprraaggmmaa not understood by traditional C by indenting them. Some
traditional implementations would not recognize ##eelliiff, so it
suggests avoiding it altogether.
-
*
A function-like macro that appears without arguments.
-
-
*
The unary plus operator.
-
-
*
The UU integer constant suffix, or the FF or LL floating point
-
constant suffixes. (Traditional C does support the LL suffix on integer
constants.) Note, these suffixes appear in macros defined in the system
headers of most modern systems, e.g. the __MMIINN/__MMAAXX macros in "".
Use of these macros in user code might normally lead to spurious
warnings, however GCC's integrated preprocessor has enough context to
avoid warning in these cases.
-
*
A function declared external in one block and then used after the end of
-
the block.
-
*
A "switch" statement has an operand of type "long".
-
-
*
A non-"static" function declaration follows a "static" one.
-
This construct is not accepted by some traditional C compilers.
-
*
The ISO type of an integer constant has a different width or
-
signedness from its traditional type. This warning is only issued if
the base of the constant is ten. I.e. hexadecimal or octal values, which
typically represent bit patterns, are not warned about.
-
*
Usage of ISO string concatenation is detected.
-
-
*
Initialization of automatic aggregates.
-
-
*
Identifier conflicts with labels. Traditional C lacks a separate
-
namespace for labels.
-
*
Initialization of unions. If the initializer is zero, the warning is
-
omitted. This is done under the assumption that the zero initializer in
user code appears conditioned on e.g. "__STDC__" to avoid missing
initializer warnings and relies on default initialization to zero in the
traditional C case.
-
*
Conversions by prototypes between fixed/floating point values and vice
-
versa. The absence of these prototypes when compiling with traditional
C would cause serious problems. This is a subset of the possible
conversion warnings, for the full set use --WWccoonnvveerrssiioonn.
-
*
Use of ISO C style function definitions. This warning intentionally is
-
_n_o_t issued for prototype declarations or variadic functions
because these ISO C features will appear in your code when using
libiberty's traditional C compatibility macros, "PARAMS" and
"VPARAMS". This warning is also bypassed for nested functions
because that feature is already a GCC extension and thus not relevant to
traditional C compatibility.
-
--WWddeeccllaarraattiioonn--aafftteerr--ssttaatteemmeenntt (C only)
Warn when a declaration is found after a statement in a block. This
-
construct, known from C++, was introduced with ISO C99 and is by default
allowed in GCC. It is not supported by ISO C90 and was not supported by
GCC versions before GCC 3.0.
-
--WWuunnddeeff
Warn if an undefined identifier is evaluated in an ##iiff directive.
-
-
--WWnnoo--eennddiiff--llaabbeellss
Do not warn whenever an ##eellssee or an ##eennddiiff are followed by text.
-
-
--WWsshhaaddooww
Warn whenever a local variable shadows another local variable, parameter or
-
global variable or whenever a built-in function is shadowed.
-
--WWllaarrggeerr--tthhaann--_l_e_n
Warn whenever an object of larger than _l_e_n bytes is defined.
-
-
--WWuunnssaaffee--lloooopp--ooppttiimmiizzaattiioonnss
Warn if the loop cannot be optimized because the compiler could not
-
assume anything on the bounds of the loop indices. With
--ffuunnssaaffee--lloooopp--ooppttiimmiizzaattiioonnss warn if the compiler made
such assumptions.
-
--WWppooiinntteerr--aarriitthh
Warn about anything that depends on the "size of" a function type or
-
of "void". GNU C assigns these types a size of 1, for
convenience in calculations with "void *" pointers and pointers
to functions.
-
--WWbbaadd--ffuunnccttiioonn--ccaasstt (C only)
Warn whenever a function call is cast to a non-matching type.
-
For example, warn if "int malloc()" is cast to "anything *".
-
--WWcc++++--ccoommppaatt
Warn about ISO C constructs that are outside of the common subset of
-
ISO C and ISO C++, e.g. request for implicit conversion from
"void *" to a pointer to non-"void" type.
-
--WWccaasstt--qquuaall
Warn whenever a pointer is cast so as to remove a type qualifier from
-
the target type. For example, warn if a "const char *" is cast
to an ordinary "char *".
-
--WWccaasstt--aalliiggnn
Warn whenever a pointer is cast such that the required alignment of the
-
target is increased. For example, warn if a "char *" is cast to
an "int *" on machines where integers can only be accessed at
two- or four-byte boundaries.
-
--WWwwrriittee--ssttrriinnggss
When compiling C, give string constants the type "const
-
char[length]" so that
copying the address of one into a non-"const" "char *"
pointer will get a warning; when compiling C++, warn about the
deprecated conversion from string constants to "char *".
These warnings will help you find at
compile time code that can try to write into a string constant, but
only if you have been very careful about using "const" in
declarations and prototypes. Otherwise, it will just be a nuisance;
this is why we did not make --WWaallll request these warnings.
-
--WWccoonnvveerrssiioonn
Warn if a prototype causes a type conversion that is different from what
-
would happen to the same argument in the absence of a prototype. This
includes conversions of fixed point to floating and vice versa, and
conversions changing the width or signedness of a fixed point argument
except when the same as the default promotion.
Also, warn if a negative integer constant expression is implicitly
converted to an unsigned type. For example, warn about the assignment
"x = -1" if "x" is unsigned. But do not warn about explicit
casts like "(unsigned) -1".
-
--WWssiiggnn--ccoommppaarree
Warn when a comparison between signed and unsigned values could produce
-
an incorrect result when the signed value is converted to unsigned.
This warning is also enabled by --WWeexxttrraa; to get the other warnings
of --WWeexxttrraa without this warning, use --WWeexxttrraa --WWnnoo--ssiiggnn--ccoommppaarree.
-
--WWaaggggrreeggaattee--rreettuurrnn
Warn if any functions that return structures or unions are defined or
-
called. (In languages where you can return an array, this also elicits
a warning.)
-
--WWnnoo--aattttrriibbuutteess
Do not warn if an unexpected "__attribute__" is used, such as
-
unrecognized attributes, function attributes applied to variables,
etc. This will not stop errors for incorrect use of supported
attributes.
-
--WWssttrriicctt--pprroottoottyyppeess (C only)
Warn if a function is declared or defined without specifying the
-
argument types. (An old-style function definition is permitted without
a warning if preceded by a declaration which specifies the argument
types.)
-
--WWoolldd--ssttyyllee--ddeeffiinniittiioonn (C only)
Warn if an old-style function definition is used. A warning is given
-
even if there is a previous prototype.
-
--WWmmiissssiinngg--pprroottoottyyppeess (C only)
Warn if a global function is defined without a previous prototype
-
declaration. This warning is issued even if the definition itself
provides a prototype. The aim is to detect global functions that fail
to be declared in header files.
-
--WWmmiissssiinngg--ddeeccllaarraattiioonnss (C only)
Warn if a global function is defined without a previous declaration.
-
Do so even if the definition itself provides a prototype.
Use this option to detect global functions that are not declared in
header files.
-
--WWmmiissssiinngg--ffiieelldd--iinniittiiaalliizzeerrss
Warn if a structure's initializer has some fields missing. For
-
example, the following code would cause such a warning, because
"x.h" is implicitly zero:
struct s { int f, g, h; };
struct s x = { 3, 4 };
This option does not warn about designated initializers, so the following
modification would not trigger a warning:
struct s { int f, g, h; };
struct s x = { .f = 3, .g = 4 };
This warning is included in --WWeexxttrraa. To get other --WWeexxttrraa
warnings without this one, use --WWeexxttrraa --WWnnoo--mmiissssiinngg--ffiieelldd--iinniittiiaalliizzeerrss.
-
--WWmmiissssiinngg--nnoorreettuurrnn
Warn about functions which might be candidates for attribute "noreturn".
-
Note these are only possible candidates, not absolute ones. Care should
be taken to manually verify functions actually do not ever return before
adding the "noreturn" attribute, otherwise subtle code generation
bugs could be introduced. You will not get a warning for "main" in
hosted C environments.
-
--WWmmiissssiinngg--ffoorrmmaatt--aattttrriibbuuttee
Warn about function pointers which might be candidates for "format"
-
attributes. Note these are only possible candidates, not absolute ones.
GCC will guess that function pointers with "format" attributes that
are used in assignment, initialization, parameter passing or return
statements should have a corresponding "format" attribute in the
resulting type. I.e. the left-hand side of the assignment or
initialization, the type of the parameter variable, or the return type
of the containing function respectively should also have a "format"
attribute to avoid the warning.
GCC will also warn about function definitions which might be
candidates for "format" attributes. Again, these are only
possible candidates. GCC will guess that "format" attributes
might be appropriate for any function that calls a function like
"vprintf" or "vscanf", but this might not always be the
case, and some functions for which "format" attributes are
appropriate may not be detected.
-
--WWnnoo--mmuullttiicchhaarr
Do not warn if a multicharacter constant (''FFOOOOFF'') is used.
-
Usually they indicate a typo in the user's code, as they have
implementation-defined values, and should not be used in portable code.
-
--WWnnoorrmmaalliizzeedd==<>
In ISO C and ISO C++, two identifiers are different if they are
-
different sequences of characters. However, sometimes when characters
outside the basic ASCII character set are used, you can have two
different character sequences that look the same. To avoid confusion,
the ISO 10646 standard sets out some _n_o_r_m_a_l_i_z_a_t_i_o_n _r_u_l_e_s which
when applied ensure that two sequences that look the same are turned into
the same sequence. GCC can warn you if you are using identifiers which
have not been normalized; this option controls that warning.
There are four levels of warning that GCC supports. The default is
--WWnnoorrmmaalliizzeedd==nnffcc, which warns about any identifier which is
not in the ISO 10646 "C" normalized form, _N_F_C. NFC is the
recommended form for most uses.
Unfortunately, there are some characters which ISO C and ISO C++ allow
in identifiers that when turned into NFC aren't allowable as
identifiers. That is, there's no way to use these symbols in portable
ISO C or C++ and have all your identifiers in NFC.
--WWnnoorrmmaalliizzeedd==iidd suppresses the warning for these characters.
It is hoped that future versions of the standards involved will correct
this, which is why this option is not the default.
You can switch the warning off for all characters by writing
--WWnnoorrmmaalliizzeedd==nnoonnee. You would only want to do this if you
were using some other normalization scheme (like "D"), because
otherwise you can easily create bugs that are literally impossible to see.
Some characters in ISO 10646 have distinct meanings but look identical
in some fonts or display methodologies, especially once formatting has
been applied. For instance "\u207F", "SUPERSCRIPT LATIN SMALL
LETTER N", will display just like a regular "n" which has been
placed in a superscript. ISO 10646 defines the _N_F_K_C
normalisation scheme to convert all these into a standard form as
well, and GCC will warn if your code is not in NFKC if you use
--WWnnoorrmmaalliizzeedd==nnffkkcc. This warning is comparable to warning
about every identifier that contains the letter O because it might be
confused with the digit 0, and so is not the default, but may be
useful as a local coding convention if the programming environment is
unable to be fixed to display these characters distinctly.
-
--WWnnoo--ddeepprreeccaatteedd--ddeeccllaarraattiioonnss
Do not warn about uses of functions, variables, and types marked as
-
deprecated by using the "deprecated" attribute.
(@pxref{Function Attributes}, @pxref{Variable Attributes},
@pxref{Type Attributes}.)
-
--WWppaacckkeedd
Warn if a structure is given the packed attribute, but the packed
-
attribute has no effect on the layout or size of the structure.
Such structures may be mis-aligned for little benefit. For
instance, in this code, the variable "f.x" in "struct bar"
will be misaligned even though "struct bar" does not itself
have the packed attribute:
struct foo {
int x;
char a, b, c, d;
} __attribute__((packed));
struct bar {
char z;
struct foo f;
};
-
--WWppaaddddeedd
Warn if padding is included in a structure, either to align an element
-
of the structure or to align the whole structure. Sometimes when this
happens it is possible to rearrange the fields of the structure to
reduce the padding and so make the structure smaller.
-
--WWrreedduunnddaanntt--ddeeccllss
Warn if anything is declared more than once in the same scope, even in
-
cases where multiple declaration is valid and changes nothing.
-
--WWnneesstteedd--eexxtteerrnnss (C only)
Warn if an "extern" declaration is encountered within a function.
-
-
--WWuunnrreeaacchhaabbllee--ccooddee
Warn if the compiler detects that code will never be executed.
-
This option is intended to warn when the compiler detects that at
least a whole line of source code will never be executed, because
some condition is never satisfied or because it is after a
procedure that never returns.
It is possible for this option to produce a warning even though there
are circumstances under which part of the affected line can be executed,
so care should be taken when removing apparently-unreachable code.
For instance, when a function is inlined, a warning may mean that the
line is unreachable in only one inlined copy of the function.
This option is not made part of --WWaallll because in a debugging
version of a program there is often substantial code which checks
correct functioning of the program and is, hopefully, unreachable
because the program does work. Another common use of unreachable
code is to provide behavior which is selectable at compile-time.
-
--WWiinnlliinnee
Warn if a function can not be inlined and it was declared as inline.
-
Even with this option, the compiler will not warn about failures to
inline functions declared in system headers.
The compiler uses a variety of heuristics to determine whether or not
to inline a function. For example, the compiler takes into account
the size of the function being inlined and the amount of inlining
that has already been done in the current function. Therefore,
seemingly insignificant changes in the source program can cause the
warnings produced by --WWiinnlliinnee to appear or disappear.
-
--WWnnoo--iinnvvaalliidd--ooffffsseettooff (C++ only)
Suppress warnings from applying the ooffffsseettooff macro to a non-POD
-
type. According to the 1998 ISO C++ standard, applying ooffffsseettooff
to a non-POD type is undefined. In existing C++ implementations,
however, ooffffsseettooff typically gives meaningful results even when
applied to certain kinds of non-POD types. (Such as a simple
ssttrruucctt that fails to be a POD type only by virtue of having a
constructor.) This flag is for users who are aware that they are
writing nonportable code and who have deliberately chosen to ignore the
warning about it.
The restrictions on ooffffsseettooff may be relaxed in a future version
of the C++ standard.
-
--WWnnoo--iinntt--ttoo--ppooiinntteerr--ccaasstt (C only)
Suppress warnings from casts to pointer type of an integer of a
-
different size.
-
--WWnnoo--ppooiinntteerr--ttoo--iinntt--ccaasstt (C only)
Suppress warnings from casts from a pointer to an integer type of a
-
different size.
-
--WWiinnvvaalliidd--ppcchh
Warn if a precompiled header is found in
-
the search path but can't be used.
-
--WWlloonngg--lloonngg
Warn if lloonngg lloonngg type is used. This is default. To inhibit
-
the warning messages, use --WWnnoo--lloonngg--lloonngg. Flags
--WWlloonngg--lloonngg and --WWnnoo--lloonngg--lloonngg are taken into account
only when --ppeeddaannttiicc flag is used.
-
--WWvvaarriiaaddiicc--mmaaccrrooss
Warn if variadic macros are used in pedantic ISO C90 mode, or the GNU
-
alternate syntax when in pedantic ISO C99 mode. This is default.
To inhibit the warning messages, use --WWnnoo--vvaarriiaaddiicc--mmaaccrrooss.
-
--WWvvoollaattiillee--rreeggiisstteerr--vvaarr
Warn if a register variable is declared volatile. The volatile
-
modifier does not inhibit all optimizations that may eliminate reads
and/or writes to register variables.
-
--WWddiissaabblleedd--ooppttiimmiizzaattiioonn
Warn if a requested optimization pass is disabled. This warning does
-
not generally indicate that there is anything wrong with your code; it
merely indicates that GCC's optimizers were unable to handle the code
effectively. Often, the problem is that your code is too big or too
complex; GCC will refuse to optimize programs when the optimization
itself is likely to take inordinate amounts of time.
-
--WWppooiinntteerr--ssiiggnn
Warn for pointer argument passing or assignment with different signedness.
-
This option is only supported for C and Objective-C. It is implied by
--WWaallll and by --ppeeddaannttiicc, which can be disabled with
--WWnnoo--ppooiinntteerr--ssiiggnn.
-
--WWeerrrroorr
Make all warnings into errors.
-
-
--WWssttaacckk--pprrootteeccttoorr
This option is only active when --ffssttaacckk--pprrootteeccttoorr is active. It
-
warns about functions that will not be protected against stack smashing.
OOppttiioonnss ffoorr DDeebbuuggggiinngg YYoouurr PPrrooggrraamm oorr GGCCCC
GCC has various special options that are used for debugging
either your program or GCC:
-
--gg
Produce debugging information in the operating system's native format
-
(stabs, COFF, XCOFF, or DWARF 2). GDB can work with this debugging
information.
On most systems that use stabs format, --gg enables use of extra
debugging information that only GDB can use; this extra information
makes debugging work better in GDB but will probably make other debuggers
crash or
refuse to read the program. If you want to control for certain whether
to generate the extra information, use --ggssttaabbss++, --ggssttaabbss,
--ggxxccooffff++, --ggxxccooffff, or --ggvvmmss (see below).
GCC allows you to use --gg with
--OO. The shortcuts taken by optimized code may occasionally
produce surprising results: some variables you declared may not exist
at all; flow of control may briefly move where you did not expect it;
some statements may not be executed because they compute constant
results or their values were already at hand; some statements may
execute in different places because they were moved out of loops.
Nevertheless it proves possible to debug optimized output. This makes
it reasonable to use the optimizer for programs that might have bugs.
The following options are useful when GCC is generated with the
capability for more than one debugging format.
-
--ggggddbb
Produce debugging information for use by GDB. This means to use the
-
most expressive format available (DWARF 2, stabs, or the native format
if neither of those are supported), including GDB extensions if at all
possible.
-
--ggssttaabbss
Produce debugging information in stabs format (if that is supported),
-
without GDB extensions. This is the format used by DBX on most BSD
systems. On MIPS, Alpha and System V Release 4 systems this option
produces stabs debugging output which is not understood by DBX or SDB.
On System V Release 4 systems this option requires the GNU assembler.
-
--ffeelliimmiinnaattee--uunnuusseedd--ddeebbuugg--ssyymmbboollss
Produce debugging information in stabs format (if that is supported),
-
for only symbols that are actually used.
-
--ggssttaabbss++
Produce debugging information in stabs format (if that is supported),
-
using GNU extensions understood only by the GNU debugger (GDB). The
use of these extensions is likely to make other debuggers crash or
refuse to read the program.
-
--ggccooffff
Produce debugging information in COFF format (if that is supported).
-
This is the format used by SDB on most System V systems prior to
System V Release 4.
-
--ggxxccooffff
Produce debugging information in XCOFF format (if that is supported).
-
This is the format used by the DBX debugger on IBM RS/6000 systems.
-
--ggxxccooffff++
Produce debugging information in XCOFF format (if that is supported),
-
using GNU extensions understood only by the GNU debugger (GDB). The
use of these extensions is likely to make other debuggers crash or
refuse to read the program, and may cause assemblers other than the GNU
assembler (GAS) to fail with an error.
-
--ggddwwaarrff--22
Produce debugging information in DWARF version 2 format (if that is
-
supported). This is the format used by DBX on IRIX 6. With this
option, GCC uses features of DWARF version 3 when they are useful;
version 3 is upward compatible with version 2, but may still cause
problems for older debuggers.
-
--ggvvmmss
Produce debugging information in VMS debug format (if that is
-
supported). This is the format used by DEBUG on VMS systems.
-
--gg_l_e_v_e_l
-
-
--ggggddbb_l_e_v_e_l
-
-
--ggssttaabbss_l_e_v_e_l
-
-
--ggccooffff_l_e_v_e_l
-
-
--ggxxccooffff_l_e_v_e_l
-
-
--ggvvmmss_l_e_v_e_l
Request debugging information and also use _l_e_v_e_l to specify how
-
much information. The default level is 2.
Level 1 produces minimal information, enough for making backtraces in
parts of the program that you don't plan to debug. This includes
descriptions of functions and external variables, but no information
about local variables and no line numbers.
Level 3 includes extra information, such as all the macro definitions
present in the program. Some debuggers support macro expansion when
you use --gg33.
--ggddwwaarrff--22 does not accept a concatenated debug level, because
GCC used to support an option --ggddwwaarrff that meant to generate
debug information in version 1 of the DWARF format (which is very
different from version 2), and it would have been too confusing. That
debug format is long obsolete, but the option cannot be changed now.
Instead use an additional --gg_l_e_v_e_l option to change the
debug level for DWARF2.
-
--ffeelliimmiinnaattee--ddwwaarrff22--dduuppss
Compress DWARF2 debugging information by eliminating duplicated
-
information about each symbol. This option only makes sense when
generating DWARF2 debugging information with --ggddwwaarrff--22.
-
--pp
Generate extra code to write profile information suitable for the
-
analysis program pprrooff. You must use this option when compiling
the source files you want data about, and you must also use it when
linking.
-
--ppgg
Generate extra code to write profile information suitable for the
-
analysis program ggpprrooff. You must use this option when compiling
the source files you want data about, and you must also use it when
linking.
-
--QQ
Makes the compiler print out each function name as it is compiled, and
-
print some statistics about each pass when it finishes.
-
--ffttiimmee--rreeppoorrtt
Makes the compiler print some statistics about the time consumed by each
-
pass when it finishes.
-
--ffmmeemm--rreeppoorrtt
Makes the compiler print some statistics about permanent memory
-
allocation when it finishes.
-
--ffpprrooffiillee--aarrccss
Add code so that program flow _a_r_c_s are instrumented. During
-
execution the program records how many times each branch and call is
executed and how many times it is taken or returns. When the compiled
program exits it saves this data to a file called
_a_u_x_n_a_m_e_._g_c_d_a for each source file. The data may be used for
profile-directed optimizations (--ffbbrraanncchh--pprroobbaabbiilliittiieess), or for
test coverage analysis (--fftteesstt--ccoovveerraaggee). Each object file's
_a_u_x_n_a_m_e is generated from the name of the output file, if
explicitly specified and it is not the final executable, otherwise it is
the basename of the source file. In both cases any suffix is removed
(e.g. _f_o_o_._g_c_d_a for input file _d_i_r_/_f_o_o_._c, or
_d_i_r_/_f_o_o_._g_c_d_a for output file specified as --oo ddiirr//ffoooo..oo).
-
----ccoovveerraaggee
This option is used to compile and link code instrumented for coverage
-
analysis. The option is a synonym for --ffpprrooffiillee--aarrccss
--fftteesstt--ccoovveerraaggee (when compiling) and --llggccoovv (when
linking). See the documentation for those options for more details.
-
@bullet
Compile the source files with --ffpprrooffiillee--aarrccss plus optimization
-
and code generation options. For test coverage analysis, use the
additional --fftteesstt--ccoovveerraaggee option. You do not need to profile
every source file in a program.
-
@cvmmfu
Link your object files with --llggccoovv or --ffpprrooffiillee--aarrccss
-
(the latter implies the former).
-
@dwnngv
Run the program on a representative workload to generate the arc profile
-
information. This may be repeated any number of times. You can run
concurrent instances of your program, and provided that the file system
supports locking, the data files will be correctly updated. Also
"fork" calls are detected and correctly handled (double counting
will not happen).
-
@exoohw
For profile-directed optimizations, compile the source files again with
-
the same optimization and code generation options plus
--ffbbrraanncchh--pprroobbaabbiilliittiieess.
-
@fyppix
For test coverage analysis, use ggccoovv to produce human readable
-
information from the _._g_c_n_o and _._g_c_d_a files. Refer to the
ggccoovv documentation for further information.
With --ffpprrooffiillee--aarrccss, for each function of your program GCC
creates a program flow graph, then finds a spanning tree for the graph.
Only arcs that are not on the spanning tree have to be instrumented: the
compiler adds code to count the number of times that these arcs are
executed. When an arc is the only exit or only entrance to a block, the
instrumentation code can be added to the block; otherwise, a new basic
block must be created to hold the instrumentation code.
-
--fftteesstt--ccoovveerraaggee
Produce a notes file that the ggccoovv code-coverage utility can use to
-
show program coverage. Each source file's note file is called
_a_u_x_n_a_m_e_._g_c_n_o. Refer to the --ffpprrooffiillee--aarrccss option
above for a description of _a_u_x_n_a_m_e and instructions on how to
generate test coverage data. Coverage data will match the source files
more closely, if you do not optimize.
-
--dd_l_e_t_t_e_r_s
-
-
--ffdduummpp--rrttll--_p_a_s_s
Says to make debugging dumps during compilation at times specified by
-
_l_e_t_t_e_r_s. This is used for debugging the RTL-based passes of the
compiler. The file names for most of the dumps are made by appending a
pass number and a word to the _d_u_m_p_n_a_m_e. _d_u_m_p_n_a_m_e is generated
from the name of the output file, if explicitly specified and it is not
an executable, otherwise it is the basename of the source file.
Most debug dumps can be enabled either passing a letter to the --dd
option, or with a long --ffdduummpp--rrttll switch; here are the possible
letters for use in _l_e_t_t_e_r_s and _p_a_s_s, and their meanings:
-
--ddAA
Annotate the assembler output with miscellaneous debugging information.
-
-
--ddbb
-
-
--ffdduummpp--rrttll--bbpp
Dump after computing branch probabilities, to _f_i_l_e_._0_9_._b_p.
-
-
--ddBB
-
-
--ffdduummpp--rrttll--bbbbrroo
Dump after block reordering, to _f_i_l_e_._3_0_._b_b_r_o.
-
-
--ddcc
-
-
--ffdduummpp--rrttll--ccoommbbiinnee
Dump after instruction combination, to the file _f_i_l_e_._1_7_._c_o_m_b_i_n_e.
-
-
--ddCC
-
-
--ffdduummpp--rrttll--ccee11
-
-
--ffdduummpp--rrttll--ccee22
--ddCC and --ffdduummpp--rrttll--ccee11 enable dumping after the
-
first if conversion, to the file _f_i_l_e_._1_1_._c_e_1. --ddCC
and --ffdduummpp--rrttll--ccee22 enable dumping after the second if
conversion, to the file _f_i_l_e_._1_8_._c_e_2.
-
--dddd
-
-
--ffdduummpp--rrttll--bbttll
-
-
--ffdduummpp--rrttll--ddbbrr
--dddd and --ffdduummpp--rrttll--bbttll enable dumping after branch
-
target load optimization, to _f_i_l_e_._3_1_._b_t_l. --dddd
and --ffdduummpp--rrttll--ddbbrr enable dumping after delayed branch
scheduling, to _f_i_l_e_._3_6_._d_b_r.
-
--ddDD
Dump all macro definitions, at the end of preprocessing, in addition to
-
normal output.
-
--ddEE
-
-
--ffdduummpp--rrttll--ccee33
Dump after the third if conversion, to _f_i_l_e_._2_8_._c_e_3.
-
-
--ddff
-
-
--ffdduummpp--rrttll--ccffgg
-
-
--ffdduummpp--rrttll--lliiffee
--ddff and --ffdduummpp--rrttll--ccffgg enable dumping after control
-
and data flow analysis, to _f_i_l_e_._0_8_._c_f_g. --ddff
and --ffdduummpp--rrttll--ccffgg enable dumping dump after life analysis,
to _f_i_l_e_._1_6_._l_i_f_e.
-
--ddgg
-
-
--ffdduummpp--rrttll--ggrreegg
Dump after global register allocation, to _f_i_l_e_._2_3_._g_r_e_g.
-
-
--ddGG
-
-
--ffdduummpp--rrttll--ggccssee
-
-
--ffdduummpp--rrttll--bbyyppaassss
--ddGG and --ffdduummpp--rrttll--ggccssee enable dumping after GCSE, to
-
_f_i_l_e_._0_5_._g_c_s_e. --ddGG and --ffdduummpp--rrttll--bbyyppaassss
enable dumping after jump bypassing and control flow optimizations, to
_f_i_l_e_._0_7_._b_y_p_a_s_s.
-
--ddhh
-
-
--ffdduummpp--rrttll--eehh
Dump after finalization of EH handling code, to _f_i_l_e_._0_2_._e_h.
-
-
--ddii
-
-
--ffdduummpp--rrttll--ssiibblliinngg
Dump after sibling call optimizations, to _f_i_l_e_._0_1_._s_i_b_l_i_n_g.
-
-
--ddjj
-
-
--ffdduummpp--rrttll--jjuummpp
Dump after the first jump optimization, to _f_i_l_e_._0_3_._j_u_m_p.
-
-
--ddkk
-
-
--ffdduummpp--rrttll--ssttaacckk
Dump after conversion from registers to stack, to _f_i_l_e_._3_3_._s_t_a_c_k.
-
-
--ddll
-
-
--ffdduummpp--rrttll--llrreegg
Dump after local register allocation, to _f_i_l_e_._2_2_._l_r_e_g.
-
-
--ddLL
-
-
--ffdduummpp--rrttll--lloooopp
-
-
--ffdduummpp--rrttll--lloooopp22
--ddLL and --ffdduummpp--rrttll--lloooopp enable dumping after the first
-
loop optimization pass, to _f_i_l_e_._0_6_._l_o_o_p. --ddLL and
--ffdduummpp--rrttll--lloooopp22 enable dumping after the second pass, to
_f_i_l_e_._1_3_._l_o_o_p_2.
-
--ddmm
-
-
--ffdduummpp--rrttll--ssmmss
Dump after modulo scheduling, to _f_i_l_e_._2_0_._s_m_s.
-
-
--ddMM
-
-
--ffdduummpp--rrttll--mmaacchh
Dump after performing the machine dependent reorganization pass, to
-
_f_i_l_e_._3_5_._m_a_c_h.
-
--ddnn
-
-
--ffdduummpp--rrttll--rrnnrreegg
Dump after register renumbering, to _f_i_l_e_._2_9_._r_n_r_e_g.
-
-
--ddNN
-
-
--ffdduummpp--rrttll--rreeggmmoovvee
Dump after the register move pass, to _f_i_l_e_._1_9_._r_e_g_m_o_v_e.
-
-
--ddoo
-
-
--ffdduummpp--rrttll--ppoossttrreellooaadd
Dump after post-reload optimizations, to _f_i_l_e_._2_4_._p_o_s_t_r_e_l_o_a_d.
-
-
--ddrr
-
-
--ffdduummpp--rrttll--eexxppaanndd
Dump after RTL generation, to _f_i_l_e_._0_0_._e_x_p_a_n_d.
-
-
--ddRR
-
-
--ffdduummpp--rrttll--sscchheedd22
Dump after the second scheduling pass, to _f_i_l_e_._3_2_._s_c_h_e_d_2.
-
-
--ddss
-
-
--ffdduummpp--rrttll--ccssee
Dump after CSE (including the jump optimization that sometimes follows
-
CSE), to _f_i_l_e_._0_4_._c_s_e.
-
--ddSS
-
-
--ffdduummpp--rrttll--sscchheedd
Dump after the first scheduling pass, to _f_i_l_e_._2_1_._s_c_h_e_d.
-
-
--ddtt
-
-
--ffdduummpp--rrttll--ccssee22
Dump after the second CSE pass (including the jump optimization that
-
sometimes follows CSE), to _f_i_l_e_._1_5_._c_s_e_2.
-
--ddTT
-
-
--ffdduummpp--rrttll--ttrraacceerr
Dump after running tracer, to _f_i_l_e_._1_2_._t_r_a_c_e_r.
-
-
--ddVV
-
-
--ffdduummpp--rrttll--vvpptt
-
-
--ffdduummpp--rrttll--vvaarrttrraacckk
--ddVV and --ffdduummpp--rrttll--vvpptt enable dumping after the value
-
profile transformations, to _f_i_l_e_._1_0_._v_p_t. --ddVV
and --ffdduummpp--rrttll--vvaarrttrraacckk enable dumping after variable tracking,
to _f_i_l_e_._3_4_._v_a_r_t_r_a_c_k.
-
--ddww
-
-
--ffdduummpp--rrttll--ffllooww22
Dump after the second flow pass, to _f_i_l_e_._2_6_._f_l_o_w_2.
-
-
--ddzz
-
-
--ffdduummpp--rrttll--ppeeeepphhoollee22
Dump after the peephole pass, to _f_i_l_e_._2_7_._p_e_e_p_h_o_l_e_2.
-
-
--ddZZ
-
-
--ffdduummpp--rrttll--wweebb
Dump after live range splitting, to _f_i_l_e_._1_4_._w_e_b.
-
-
--ddaa
-
-
--ffdduummpp--rrttll--aallll
Produce all the dumps listed above.
-
-
--ddHH
Produce a core dump whenever an error occurs.
-
-
--ddmm
Print statistics on memory usage, at the end of the run, to
-
standard error.
-
--ddpp
Annotate the assembler output with a comment indicating which
-
pattern and alternative was used. The length of each instruction is
also printed.
-
--ddPP
Dump the RTL in the assembler output as a comment before each instruction.
-
Also turns on --ddpp annotation.
-
--ddvv
For each of the other indicated dump files (either with --dd or
-
--ffdduummpp--rrttll--_p_a_s_s), dump a representation of the control flow
graph suitable for viewing with VCG to _f_i_l_e_._p_a_s_s_._v_c_g.
-
--ddxx
Just generate RTL for a function instead of compiling it. Usually used
-
with rr (--ffdduummpp--rrttll--eexxppaanndd).
-
--ddyy
Dump debugging information during parsing, to standard error.
-
-
--ffdduummpp--uunnnnuummbbeerreedd
When doing debugging dumps (see --dd option above), suppress instruction
-
numbers and line number note output. This makes it more feasible to
use diff on debugging dumps for compiler invocations with different
options, in particular with and without --gg.
-
--ffdduummpp--ttrraannssllaattiioonn--uunniitt (C++ only)
-
-
--ffdduummpp--ttrraannssllaattiioonn--uunniitt--_o_p_t_i_o_n_s (C++ only)
Dump a representation of the tree structure for the entire translation
-
unit to a file. The file name is made by appending _._t_u to the
source file name. If the --_o_p_t_i_o_n_s form is used, _o_p_t_i_o_n_s
controls the details of the dump as described for the
--ffdduummpp--ttrreeee options.
-
--ffdduummpp--ccllaassss--hhiieerraarrcchhyy (C++ only)
-
-
--ffdduummpp--ccllaassss--hhiieerraarrcchhyy--_o_p_t_i_o_n_s (C++ only)
Dump a representation of each class's hierarchy and virtual function
-
table layout to a file. The file name is made by appending _._c_l_a_s_s
to the source file name. If the --_o_p_t_i_o_n_s form is used,
_o_p_t_i_o_n_s controls the details of the dump as described for the
--ffdduummpp--ttrreeee options.
-
--ffdduummpp--iippaa--_s_w_i_t_c_h
Control the dumping at various stages of inter-procedural analysis
-
language tree to a file. The file name is generated by appending a switch
specific suffix to the source file name. The following dumps are possible:
-
aallll
Enables all inter-procedural analysis dumps; currently the only produced
-
dump is the ccggrraapphh dump.
-
ccggrraapphh
Dumps information about call-graph optimization, unused function removal,
-
and inlining decisions.
-
--ffdduummpp--ttrreeee--_s_w_i_t_c_h
-
-
--ffdduummpp--ttrreeee--_s_w_i_t_c_h--_o_p_t_i_o_n_s
Control the dumping at various stages of processing the intermediate
-
language tree to a file. The file name is generated by appending a switch
specific suffix to the source file name. If the --_o_p_t_i_o_n_s
form is used, _o_p_t_i_o_n_s is a list of -- separated options that
control the details of the dump. Not all options are applicable to all
dumps, those which are not meaningful will be ignored. The following
options are available
-
aaddddrreessss
Print the address of each node. Usually this is not meaningful as it
-
changes according to the environment and source file. Its primary use
is for tying up a dump file with a debug environment.
-
sslliimm
Inhibit dumping of members of a scope or body of a function merely
-
because that scope has been reached. Only dump such items when they
are directly reachable by some other path. When dumping pretty-printed
trees, this option inhibits dumping the bodies of control structures.
-
rraaww
Print a raw representation of the tree. By default, trees are
-
pretty-printed into a C-like representation.
-
ddeettaaiillss
Enable more detailed dumps (not honored by every dump option).
-
-
ssttaattss
Enable dumping various statistics about the pass (not honored by every dump
-
option).
-
bblloocckkss
Enable showing basic block boundaries (disabled in raw dumps).
-
-
vvooppss
Enable showing virtual operands for every statement.
-
-
lliinneennoo
Enable showing line numbers for statements.
-
-
uuiidd
Enable showing the unique ID ("DECL_UID") for each variable.
-
-
aallll
Turn on all options, except rraaww, sslliimm and lliinneennoo.
-
The following tree dumps are possible:
-
oorriiggiinnaall
Dump before any tree based optimization, to _f_i_l_e_._o_r_i_g_i_n_a_l.
-
-
ooppttiimmiizzeedd
Dump after all tree based optimization, to _f_i_l_e_._o_p_t_i_m_i_z_e_d.
-
-
iinnlliinneedd
Dump after function inlining, to _f_i_l_e_._i_n_l_i_n_e_d.
-
-
ggiimmppllee
Dump each function before and after the gimplification pass to a file. The
-
file name is made by appending _._g_i_m_p_l_e to the source file name.
-
ccffgg
Dump the control flow graph of each function to a file. The file name is
-
made by appending _._c_f_g to the source file name.
-
vvccgg
Dump the control flow graph of each function to a file in VCG format. The
-
file name is made by appending _._v_c_g to the source file name. Note
that if the file contains more than one function, the generated file cannot
be used directly by VCG. You will need to cut and paste each function's
graph into its own separate file first.
-
cchh
Dump each function after copying loop headers. The file name is made by
-
appending _._c_h to the source file name.
-
ssssaa
Dump SSA related information to a file. The file name is made by appending
-
_._s_s_a to the source file name.
-
ssaalliiaass
Dump structure aliasing variable information to a file. This file name
-
is made by appending _._s_a_l_i_a_s to the source file name.
-
aalliiaass
Dump aliasing information for each function. The file name is made by
-
appending _._a_l_i_a_s to the source file name.
-
ccccpp
Dump each function after CCP. The file name is made by appending
-
_._c_c_p to the source file name.
-
ssttoorreeccccpp
Dump each function after STORE-CCP. The file name is made by appending
-
_._s_t_o_r_e_c_c_p to the source file name.
-
pprree
Dump trees after partial redundancy elimination. The file name is made
-
by appending _._p_r_e to the source file name.
-
ffrree
Dump trees after full redundancy elimination. The file name is made
-
by appending _._f_r_e to the source file name.
-
ccooppyypprroopp
Dump trees after copy propagation. The file name is made
-
by appending _._c_o_p_y_p_r_o_p to the source file name.
-
ssttoorree__ccooppyypprroopp
Dump trees after store copy-propagation. The file name is made
-
by appending _._s_t_o_r_e___c_o_p_y_p_r_o_p to the source file name.
-
ddccee
Dump each function after dead code elimination. The file name is made by
-
appending _._d_c_e to the source file name.
-
mmuuddffllaapp
Dump each function after adding mudflap instrumentation. The file name is
-
made by appending _._m_u_d_f_l_a_p to the source file name.
-
ssrraa
Dump each function after performing scalar replacement of aggregates. The
-
file name is made by appending _._s_r_a to the source file name.
-
ssiinnkk
Dump each function after performing code sinking. The file name is made
-
by appending _._s_i_n_k to the source file name.
-
ddoomm
Dump each function after applying dominator tree optimizations. The file
-
name is made by appending _._d_o_m to the source file name.
-
ddssee
Dump each function after applying dead store elimination. The file
-
name is made by appending _._d_s_e to the source file name.
-
pphhiioopptt
Dump each function after optimizing PHI nodes into straightline code. The file
-
name is made by appending _._p_h_i_o_p_t to the source file name.
-
ffoorrwwpprroopp
Dump each function after forward propagating single use variables. The file
-
name is made by appending _._f_o_r_w_p_r_o_p to the source file name.
-
ccooppyyrreennaammee
Dump each function after applying the copy rename optimization. The file
-
name is made by appending _._c_o_p_y_r_e_n_a_m_e to the source file name.
-
nnrrvv
Dump each function after applying the named return value optimization on
-
generic trees. The file name is made by appending _._n_r_v to the source
file name.
-
vveecctt
Dump each function after applying vectorization of loops. The file name is
-
made by appending _._v_e_c_t to the source file name.
-
vvrrpp
Dump each function after Value Range Propagation (VRP). The file name
-
is made by appending _._v_r_p to the source file name.
-
aallll
Enable all the available tree dumps with the flags provided in this option.
-
-
--ffttrreeee--vveeccttoorriizzeerr--vveerrbboossee==_n
This option controls the amount of debugging output the vectorizer prints.
-
This information is written to standard error, unless --ffdduummpp--ttrreeee--aallll
or --ffdduummpp--ttrreeee--vveecctt is specified, in which case it is output to the
usual dump listing file, _._v_e_c_t.
-
--ffrraannddoomm--sseeeedd==_s_t_r_i_n_g
This option provides a seed that GCC uses when it would otherwise use
-
random numbers. It is used to generate certain symbol names
that have to be different in every compiled file. It is also used to
place unique stamps in coverage data files and the object files that
produce them. You can use the --ffrraannddoomm--sseeeedd option to produce
reproducibly identical object files.
The _s_t_r_i_n_g should be different for every file you compile.
-
--ffsscchheedd--vveerrbboossee==_n
On targets that use instruction scheduling, this option controls the
-
amount of debugging output the scheduler prints. This information is
written to standard error, unless --ddSS or --ddRR is
specified, in which case it is output to the usual dump
listing file, _._s_c_h_e_d or _._s_c_h_e_d_2 respectively. However
for _n greater than nine, the output is always printed to standard
error.
For _n greater than zero, --ffsscchheedd--vveerrbboossee outputs the
same information as --ddRRSS. For _n greater than one, it
also output basic block probabilities, detailed ready list information
and unit/insn info. For _n greater than two, it includes RTL
at abort point, control-flow and regions info. And for _n over
four, --ffsscchheedd--vveerrbboossee also includes dependence info.
-
--ssaavvee--tteemmppss
Store the usual "temporary" intermediate files permanently; place them
-
in the current directory and name them based on the source file. Thus,
compiling _f_o_o_._c with --cc --ssaavvee--tteemmppss would produce files
_f_o_o_._i and _f_o_o_._s, as well as _f_o_o_._o. This creates a
preprocessed _f_o_o_._i output file even though the compiler now
normally uses an integrated preprocessor.
When used in combination with the --xx command line option,
--ssaavvee--tteemmppss is sensible enough to avoid over writing an
input source file with the same extension as an intermediate file.
The corresponding intermediate file may be obtained by renaming the
source file before using --ssaavvee--tteemmppss.
-
--ttiimmee
Report the CPU time taken by each subprocess in the compilation
-
sequence. For C source files, this is the compiler proper and assembler
(plus the linker if linking is done). The output looks like this:
# cc1 0.12 0.01
# as 0.00 0.01
The first number on each line is the "user time", that is time spent
executing the program itself. The second number is "system time",
time spent executing operating system routines on behalf of the program.
Both numbers are in seconds.
-
--ffvvaarr--ttrraacckkiinngg
Run variable tracking pass. It computes where variables are stored at each
-
position in code. Better debugging information is then generated
(if the debugging information format supports this information).
It is enabled by default when compiling with optimization (--OOss,
--OO, --OO22, ...), debugging information (--gg) and
the debug info format supports it.
-
--pprriinntt--ffiillee--nnaammee==_l_i_b_r_a_r_y
Print the full absolute name of the library file _l_i_b_r_a_r_y that
-
would be used when linking---and don't do anything else. With this
option, GCC does not compile or link anything; it just prints the
file name.
-
--pprriinntt--mmuullttii--ddiirreeccttoorryy
Print the directory name corresponding to the multilib selected by any
-
other switches present in the command line. This directory is supposed
to exist in GGCCCC__EEXXEECC__PPRREEFFIIXX.
-
--pprriinntt--mmuullttii--lliibb
Print the mapping from multilib directory names to compiler switches
-
that enable them. The directory name is separated from the switches by
;;, and each switch starts with an @@}} iinnsstteeaadd ooff tthhee
@@ssaammpp{{--, without spaces between multiple switches. This is supposed to
ease shell-processing.
-
--pprriinntt--pprroogg--nnaammee==_p_r_o_g_r_a_m
Like --pprriinntt--ffiillee--nnaammee, but searches for a program such as ccpppp.
-
-
--pprriinntt--lliibbggcccc--ffiillee--nnaammee
Same as --pprriinntt--ffiillee--nnaammee==lliibbggcccc..aa.
-
This is useful when you use --nnoossttddlliibb or --nnooddeeffaauullttlliibbss
but you do want to link with _l_i_b_g_c_c_._a. You can do
gcc -nostdlib ... `gcc -print-libgcc-file-name`
-
--pprriinntt--sseeaarrcchh--ddiirrss
Print the name of the configured installation directory and a list of
-
program and library directories ggcccc will search---and don't do anything else.
This is useful when ggcccc prints the error message
iinnssttaallllaattiioonn pprroobblleemm,, ccaannnnoott eexxeecc ccpppp00:: NNoo ssuucchh ffiillee oorr ddiirreeccttoorryy.
To resolve this you either need to put _c_p_p_0 and the other compiler
components where ggcccc expects to find them, or you can set the environment
variable GGCCCC__EEXXEECC__PPRREEFFIIXX to the directory where you installed them.
Don't forget the trailing //.
-
--dduummppmmaacchhiinnee
Print the compiler's target machine (for example,
-
ii668866--ppcc--lliinnuuxx--ggnnuu)---and don't do anything else.
-
--dduummppvveerrssiioonn
Print the compiler version (for example, 33..00)---and don't do
-
anything else.
-
--dduummppssppeeccss
Print the compiler's built-in specs---and don't do anything else. (This
-
is used when GCC itself is being built.)
-
--ffeelliimmiinnaattee--uunnuusseedd--ddeebbuugg--ttyyppeess
Normally, when producing DWARF2 output, GCC will emit debugging
-
information for all types declared in a compilation
unit, regardless of whether or not they are actually used
in that compilation unit. Sometimes this is useful, such as
if, in the debugger, you want to cast a value to a type that is
not actually used in your program (but is declared). More often,
however, this results in a significant amount of wasted space.
With this option, GCC will avoid producing debug symbol output
for types that are nowhere used in the source file being compiled.
OOppttiioonnss TThhaatt CCoonnttrrooll OOppttiimmiizzaattiioonn
These options control various sorts of optimizations.
Without any optimization option, the compiler's goal is to reduce the
cost of compilation and to make debugging produce the expected
results. Statements are independent: if you stop the program with a
breakpoint between statements, you can then assign a new value to any
variable or change the program counter to any other statement in the
function and get exactly the results you would expect from the source
code.
Turning on optimization flags makes the compiler attempt to improve
the performance and/or code size at the expense of compilation time
and possibly the ability to debug the program.
The compiler performs optimization based on the knowledge it has of
the program. Optimization levels --OO22 and above, in
particular, enable _u_n_i_t_-_a_t_-_a_-_t_i_m_e mode, which allows the
compiler to consider information gained from later functions in
the file when compiling a function. Compiling multiple files at
once to a single output file in _u_n_i_t_-_a_t_-_a_-_t_i_m_e mode allows
the compiler to use information gained from all of the files when
compiling each of them.
Not all optimizations are controlled directly by a flag. Only
optimizations that have a flag are listed.
-
--OO
-
-
--OO11
Optimize. Optimizing compilation takes somewhat more time, and a lot
-
more memory for a large function.
With --OO, the compiler tries to reduce code size and execution
time, without performing any optimizations that take a great deal of
compilation time.
--OO turns on the following optimization flags:
--ffddeeffeerr--ppoopp
--ffddeellaayyeedd--bbrraanncchh
--ffgguueessss--bbrraanncchh--pprroobbaabbiilliittyy
--ffccpprroopp--rreeggiisstteerrss
--fflloooopp--ooppttiimmiizzee
--ffiiff--ccoonnvveerrssiioonn
--ffiiff--ccoonnvveerrssiioonn22
--ffttrreeee--ccccpp
--ffttrreeee--ddccee
--ffttrreeee--ddoommiinnaattoorr--ooppttss
--ffttrreeee--ddssee
--ffttrreeee--tteerr
--ffttrreeee--llrrss
--ffttrreeee--ssrraa
--ffttrreeee--ccooppyyrreennaammee
--ffttrreeee--ffrree
--ffttrreeee--cchh
--ffmmeerrggee--ccoonnssttaannttss
--OO also turns on --ffoommiitt--ffrraammee--ppooiinntteerr on machines
where doing so does not interfere with debugging.
--OO doesn't turn on --ffttrreeee--ssrraa for the Ada compiler.
This option must be explicitly specified on the command line to be
enabled for the Ada compiler.
-
--OO22
Optimize even more. GCC performs nearly all supported optimizations
-
that do not involve a space-speed tradeoff. The compiler does not
perform loop unrolling or function inlining when you specify --OO22.
As compared to --OO, this option increases both compilation time
and the performance of the generated code.
--OO22 turns on all optimization flags specified by --OO. It
also turns on the following optimization flags:
--fftthhrreeaadd--jjuummppss
--ffccrroossssjjuummppiinngg
--ffooppttiimmiizzee--ssiibblliinngg--ccaallllss
--ffccssee--ffoollllooww--jjuummppss --ffccssee--sskkiipp--bblloocckkss
--ffggccssee --ffggccssee--llmm
--ffeexxppeennssiivvee--ooppttiimmiizzaattiioonnss
--ffssttrreennggtthh--rreedduuccee
--ffrreerruunn--ccssee--aafftteerr--lloooopp --ffrreerruunn--lloooopp--oopptt
--ffccaalllleerr--ssaavveess
--ffppeeeepphhoollee22
--ffsscchheedduullee--iinnssnnss --ffsscchheedduullee--iinnssnnss22
--ffsscchheedd--iinntteerrbblloocckk --ffsscchheedd--ssppeecc
--ffrreeggmmoovvee
--ffssttrriicctt--aalliiaassiinngg
--ffddeelleettee--nnuullll--ppooiinntteerr--cchheecckkss
--ffrreeoorrddeerr--bblloocckkss --ffrreeoorrddeerr--ffuunnccttiioonnss
--ffuunniitt--aatt--aa--ttiimmee
--ffaalliiggnn--ffuunnccttiioonnss --ffaalliiggnn--jjuummppss
--ffaalliiggnn--llooooppss --ffaalliiggnn--llaabbeellss
--ffttrreeee--vvrrpp
--ffttrreeee--pprree
Please note the warning under --ffggccssee about
invoking --OO22 on programs that use computed gotos.
-
--OO33
Optimize yet more. --OO33 turns on all optimizations specified by
-
--OO22 and also turns on the --ffiinnlliinnee--ffuunnccttiioonnss,
--ffuunnsswwiittcchh--llooooppss and --ffggccssee--aafftteerr--rreellooaadd options.
-
--OO00
Do not optimize. This is the default.
-
-
--OOss
Optimize for size. --OOss enables all --OO22 optimizations that
-
do not typically increase code size. It also performs further
optimizations designed to reduce code size.
--OOss disables the following optimization flags:
--ffaalliiggnn--ffuunnccttiioonnss --ffaalliiggnn--jjuummppss --ffaalliiggnn--llooooppss
--ffaalliiggnn--llaabbeellss --ffrreeoorrddeerr--bblloocckkss --ffrreeoorrddeerr--bblloocckkss--aanndd--ppaarrttiittiioonn
--ffpprreeffeettcchh--lloooopp--aarrrraayyss --ffttrreeee--vveecctt--lloooopp--vveerrssiioonn
If you use multiple --OO options, with or without level numbers,
the last such option is the one that is effective.
Options of the form --ff_f_l_a_g specify machine-independent
flags. Most flags have both positive and negative forms; the negative
form of --ffffoooo would be --ffnnoo--ffoooo. In the table
below, only one of the forms is listed---the one you typically will
use. You can figure out the other form by either removing nnoo--
or adding it.
The following options control specific optimizations. They are either
activated by --OO options or are related to ones that are. You
can use the following flags in the rare cases when "fine-tuning" of
optimizations to be performed is desired.
-
--ffnnoo--ddeeffaauulltt--iinnlliinnee
Do not make member functions inline by default merely because they are
-
defined inside the class scope (C++ only). Otherwise, when you specify
--OO, member functions defined inside class scope are compiled
inline by default; i.e., you don't need to add iinnlliinnee in front of
the member function name.
-
--ffnnoo--ddeeffeerr--ppoopp
Always pop the arguments to each function call as soon as that function
-
returns. For machines which must pop arguments after a function call,
the compiler normally lets arguments accumulate on the stack for several
function calls and pops them all at once.
Disabled at levels --OO, --OO22, --OO33, --OOss.
-
--ffffoorrccee--mmeemm
Force memory operands to be copied into registers before doing
-
arithmetic on them. This produces better code by making all memory
references potential common subexpressions. When they are not common
subexpressions, instruction combination should eliminate the separate
register-load. This option is now a nop and will be removed in 4.2.
-
--ffffoorrccee--aaddddrr
Force memory address constants to be copied into registers before
-
doing arithmetic on them.
-
--ffoommiitt--ffrraammee--ppooiinntteerr
Don't keep the frame pointer in a register for functions that
-
don't need one. This avoids the instructions to save, set up and
restore frame pointers; it also makes an extra register available
in many functions. IItt aallssoo mmaakkeess ddeebbuuggggiinngg iimmppoossssiibbllee oonn
ssoommee mmaacchhiinneess..
On some machines, such as the VAX, this flag has no effect, because
the standard calling sequence automatically handles the frame pointer
and nothing is saved by pretending it doesn't exist. The
machine-description macro "FRAME_POINTER_REQUIRED" controls
whether a target machine supports this flag.
Enabled at levels --OO, --OO22, --OO33, --OOss.
-
--ffooppttiimmiizzee--ssiibblliinngg--ccaallllss
Optimize sibling and tail recursive calls.
-
Enabled at levels --OO22, --OO33, --OOss.
-
--ffnnoo--iinnlliinnee
Don't pay attention to the "inline" keyword. Normally this option
-
is used to keep the compiler from expanding any functions inline.
Note that if you are not optimizing, no functions can be expanded inline.
-
--ffiinnlliinnee--ffuunnccttiioonnss
Integrate all simple functions into their callers. The compiler
-
heuristically decides which functions are simple enough to be worth
integrating in this way.
If all calls to a given function are integrated, and the function is
declared "static", then the function is normally not output as
assembler code in its own right.
Enabled at level --OO33.
-
--ffiinnlliinnee--ffuunnccttiioonnss--ccaalllleedd--oonnccee
Consider all "static" functions called once for inlining into their
-
caller even if they are not marked "inline". If a call to a given
function is integrated, then the function is not output as assembler code
in its own right.
Enabled if --ffuunniitt--aatt--aa--ttiimmee is enabled.
-
--ffeeaarrllyy--iinnlliinniinngg
Inline functions marked by "always_inline" and functions whose body seems
-
smaller than the function call overhead early before doing
--ffpprrooffiillee--ggeenneerraattee instrumentation and real inlining pass. Doing so
makes profiling significantly cheaper and usually inlining faster on programs
having large chains of nested wrapper functions.
Enabled by default.
-
--ffiinnlliinnee--lliimmiitt==_n
By default, GCC limits the size of functions that can be inlined. This flag
-
allows the control of this limit for functions that are explicitly marked as
inline (i.e., marked with the inline keyword or defined within the class
definition in c++). _n is the size of functions that can be inlined in
number of pseudo instructions (not counting parameter handling). The default
value of _n is 600.
Increasing this value can result in more inlined code at
the cost of compilation time and memory consumption. Decreasing usually makes
the compilation faster and less code will be inlined (which presumably
means slower programs). This option is particularly useful for programs that
use inlining heavily such as those based on recursive templates with C++.
Inlining is actually controlled by a number of parameters, which may be
specified individually by using ----ppaarraamm _n_a_m_e==_v_a_l_u_e.
The --ffiinnlliinnee--lliimmiitt==_n option sets some of these parameters
as follows:
@item max-inline-insns-single
is set to I/2.
@item max-inline-insns-auto
is set to I/2.
@item min-inline-insns
is set to 130 or I/4, whichever is smaller.
@item max-inline-insns-rtl
is set to I.
See below for a documentation of the individual
parameters controlling inlining.
_N_o_t_e_: pseudo instruction represents, in this particular context, an
abstract measurement of function's size. In no way does it represent a count
of assembly instructions and as such its exact meaning might change from one
release to an another.
-
--ffkkeeeepp--iinnlliinnee--ffuunnccttiioonnss
In C, emit "static" functions that are declared "inline"
-
into the object file, even if the function has been inlined into all
of its callers. This switch does not affect functions using the
"extern inline" extension in GNU C. In C++, emit any and all
inline functions into the object file.
-
--ffkkeeeepp--ssttaattiicc--ccoonnssttss
Emit variables declared "static const" when optimization isn't turned
-
on, even if the variables aren't referenced.
GCC enables this option by default. If you want to force the compiler to
check if the variable was referenced, regardless of whether or not
optimization is turned on, use the --ffnnoo--kkeeeepp--ssttaattiicc--ccoonnssttss option.
-
--ffmmeerrggee--ccoonnssttaannttss
Attempt to merge identical constants (string constants and floating point
-
constants) across compilation units.
This option is the default for optimized compilation if the assembler and
linker support it. Use --ffnnoo--mmeerrggee--ccoonnssttaannttss to inhibit this
behavior.
Enabled at levels --OO, --OO22, --OO33, --OOss.
-
--ffmmeerrggee--aallll--ccoonnssttaannttss
Attempt to merge identical constants and identical variables.
-
This option implies --ffmmeerrggee--ccoonnssttaannttss. In addition to
--ffmmeerrggee--ccoonnssttaannttss this considers e.g. even constant initialized
arrays or initialized constant variables with integral or floating point
types. Languages like C or C++ require each non-automatic variable to
have distinct location, so using this option will result in non-conforming
behavior.
-
--ffmmoodduulloo--sscchheedd
Perform swing modulo scheduling immediately before the first scheduling
-
pass. This pass looks at innermost loops and reorders their
instructions by overlapping different iterations.
-
--ffnnoo--bbrraanncchh--ccoouunntt--rreegg
Do not use "decrement and branch" instructions on a count register,
-
but instead generate a sequence of instructions that decrement a
register, compare it against zero, then branch based upon the result.
This option is only meaningful on architectures that support such
instructions, which include x86, PowerPC, IA-64 and S/390.
The default is --ffbbrraanncchh--ccoouunntt--rreegg, enabled when
--ffssttrreennggtthh--rreedduuccee is enabled.
-
--ffnnoo--ffuunnccttiioonn--ccssee
Do not put function addresses in registers; make each instruction that
-
calls a constant function contain the function's address explicitly.
This option results in less efficient code, but some strange hacks
that alter the assembler output may be confused by the optimizations
performed when this option is not used.
The default is --ffffuunnccttiioonn--ccssee
-
--ffnnoo--zzeerroo--iinniittiiaalliizzeedd--iinn--bbssss
If the target supports a BSS section, GCC by default puts variables that
-
are initialized to zero into BSS. This can save space in the resulting
code.
This option turns off this behavior because some programs explicitly
rely on variables going to the data section. E.g., so that the
resulting executable can find the beginning of that section and/or make
assumptions based on that.
The default is --ffzzeerroo--iinniittiiaalliizzeedd--iinn--bbssss.
-
--ffbboouunnddss--cchheecckk
For front-ends that support it, generate additional code to check that
-
indices used to access arrays are within the declared range. This is
currently only supported by the Java and Fortran front-ends, where
this option defaults to true and false respectively.
-
--ffmmuuddffllaapp --ffmmuuddffllaapptthh --ffmmuuddffllaappiirr
For front-ends that support it (C and C++), instrument all risky
-
pointer/array dereferencing operations, some standard library
string/heap functions, and some other associated constructs with
range/validity tests. Modules so instrumented should be immune to
buffer overflows, invalid heap use, and some other classes of C/C++
programming errors. The instrumentation relies on a separate runtime
library (_l_i_b_m_u_d_f_l_a_p), which will be linked into a program if
--ffmmuuddffllaapp is given at link time. Run-time behavior of the
instrumented program is controlled by the MMUUDDFFLLAAPP__OOPPTTIIOONNSS
environment variable. See "env MUDFLAP_OPTIONS=-help a.out"
for its options.
Use --ffmmuuddffllaapptthh instead of --ffmmuuddffllaapp to compile and to
link if your program is multi-threaded. Use --ffmmuuddffllaappiirr, in
addition to --ffmmuuddffllaapp or --ffmmuuddffllaapptthh, if
instrumentation should ignore pointer reads. This produces less
instrumentation (and therefore faster execution) and still provides
some protection against outright memory corrupting writes, but allows
erroneously read data to propagate within a program.
-
--ffssttrreennggtthh--rreedduuccee
Perform the optimizations of loop strength reduction and
-
elimination of iteration variables.
Enabled at levels --OO22, --OO33, --OOss.
-
--fftthhrreeaadd--jjuummppss
Perform optimizations where we check to see if a jump branches to a
-
location where another comparison subsumed by the first is found. If
so, the first branch is redirected to either the destination of the
second branch or a point immediately following it, depending on whether
the condition is known to be true or false.
Enabled at levels --OO22, --OO33, --OOss.
-
--ffccssee--ffoollllooww--jjuummppss
In common subexpression elimination, scan through jump instructions
-
when the target of the jump is not reached by any other path. For
example, when CSE encounters an "if" statement with an
"else" clause, CSE will follow the jump when the condition
tested is false.
Enabled at levels --OO22, --OO33, --OOss.
-
--ffccssee--sskkiipp--bblloocckkss
This is similar to --ffccssee--ffoollllooww--jjuummppss, but causes CSE to
-
follow jumps which conditionally skip over blocks. When CSE
encounters a simple "if" statement with no else clause,
--ffccssee--sskkiipp--bblloocckkss causes CSE to follow the jump around the
body of the "if".
Enabled at levels --OO22, --OO33, --OOss.
-
--ffrreerruunn--ccssee--aafftteerr--lloooopp
Re-run common subexpression elimination after loop optimizations has been
-
performed.
Enabled at levels --OO22, --OO33, --OOss.
-
--ffrreerruunn--lloooopp--oopptt
Run the loop optimizer twice.
-
Enabled at levels --OO22, --OO33, --OOss.
-
--ffggccssee
Perform a global common subexpression elimination pass.
-
This pass also performs global constant and copy propagation.
_N_o_t_e_: When compiling a program using computed gotos, a GCC
extension, you may get better runtime performance if you disable
the global common subexpression elimination pass by adding
--ffnnoo--ggccssee to the command line.
Enabled at levels --OO22, --OO33, --OOss.
-
--ffggccssee--llmm
When --ffggccssee--llmm is enabled, global common subexpression elimination will
-
attempt to move loads which are only killed by stores into themselves. This
allows a loop containing a load/store sequence to be changed to a load outside
the loop, and a copy/store within the loop.
Enabled by default when gcse is enabled.
-
--ffggccssee--ssmm
When --ffggccssee--ssmm is enabled, a store motion pass is run after
-
global common subexpression elimination. This pass will attempt to move
stores out of loops. When used in conjunction with --ffggccssee--llmm,
loops containing a load/store sequence can be changed to a load before
the loop and a store after the loop.
Not enabled at any optimization level.
-
--ffggccssee--llaass
When --ffggccssee--llaass is enabled, the global common subexpression
-
elimination pass eliminates redundant loads that come after stores to the
same memory location (both partial and full redundancies).
Not enabled at any optimization level.
-
--ffggccssee--aafftteerr--rreellooaadd
When --ffggccssee--aafftteerr--rreellooaadd is enabled, a redundant load elimination
-
pass is performed after reload. The purpose of this pass is to cleanup
redundant spilling.
-
--fflloooopp--ooppttiimmiizzee
Perform loop optimizations: move constant expressions out of loops, simplify
-
exit test conditions and optionally do strength-reduction as well.
Enabled at levels --OO, --OO22, --OO33, --OOss.
-
--fflloooopp--ooppttiimmiizzee22
Perform loop optimizations using the new loop optimizer. The optimizations
-
(loop unrolling, peeling and unswitching, loop invariant motion) are enabled
by separate flags.
-
--ffuunnssaaffee--lloooopp--ooppttiimmiizzaattiioonnss
If given, the loop optimizer will assume that loop indices do not
-
overflow, and that the loops with nontrivial exit condition are not
infinite. This enables a wider range of loop optimizations even if
the loop optimizer itself cannot prove that these assumptions are valid.
Using --WWuunnssaaffee--lloooopp--ooppttiimmiizzaattiioonnss, the compiler will warn you
if it finds this kind of loop.
-
--ffccrroossssjjuummppiinngg
Perform cross-jumping transformation. This transformation unifies equivalent code and save code size. The
-
resulting code may or may not perform better than without cross-jumping.
Enabled at levels --OO22, --OO33, --OOss.
-
--ffiiff--ccoonnvveerrssiioonn
Attempt to transform conditional jumps into branch-less equivalents. This
-
include use of conditional moves, min, max, set flags and abs instructions, and
some tricks doable by standard arithmetics. The use of conditional execution
on chips where it is available is controlled by "if-conversion2".
Enabled at levels --OO, --OO22, --OO33, --OOss.
-
--ffiiff--ccoonnvveerrssiioonn22
Use conditional execution (where available) to transform conditional jumps into
-
branch-less equivalents.
Enabled at levels --OO, --OO22, --OO33, --OOss.
-
--ffddeelleettee--nnuullll--ppooiinntteerr--cchheecckkss
Use global dataflow analysis to identify and eliminate useless checks
-
for null pointers. The compiler assumes that dereferencing a null
pointer would have halted the program. If a pointer is checked after
it has already been dereferenced, it cannot be null.
In some environments, this assumption is not true, and programs can
safely dereference null pointers. Use
--ffnnoo--ddeelleettee--nnuullll--ppooiinntteerr--cchheecckkss to disable this optimization
for programs which depend on that behavior.
Enabled at levels --OO22, --OO33, --OOss.
-
--ffeexxppeennssiivvee--ooppttiimmiizzaattiioonnss
Perform a number of minor optimizations that are relatively expensive.
-
Enabled at levels --OO22, --OO33, --OOss.
-
--ffooppttiimmiizzee--rreeggiisstteerr--mmoovvee
-
-
--ffrreeggmmoovvee
Attempt to reassign register numbers in move instructions and as
-
operands of other simple instructions in order to maximize the amount of
register tying. This is especially helpful on machines with two-operand
instructions.
Note --ffrreeggmmoovvee and --ffooppttiimmiizzee--rreeggiisstteerr--mmoovvee are the same
optimization.
Enabled at levels --OO22, --OO33, --OOss.
-
--ffddeellaayyeedd--bbrraanncchh
If supported for the target machine, attempt to reorder instructions
-
to exploit instruction slots available after delayed branch
instructions.
Enabled at levels --OO, --OO22, --OO33, --OOss.
-
--ffsscchheedduullee--iinnssnnss
If supported for the target machine, attempt to reorder instructions to
-
eliminate execution stalls due to required data being unavailable. This
helps machines that have slow floating point or memory load instructions
by allowing other instructions to be issued until the result of the load
or floating point instruction is required.
Enabled at levels --OO22, --OO33, --OOss.
-
--ffsscchheedduullee--iinnssnnss22
Similar to --ffsscchheedduullee--iinnssnnss, but requests an additional pass of
-
instruction scheduling after register allocation has been done. This is
especially useful on machines with a relatively small number of
registers and where memory load instructions take more than one cycle.
Enabled at levels --OO22, --OO33, --OOss.
-
--ffnnoo--sscchheedd--iinntteerrbblloocckk
Don't schedule instructions across basic blocks. This is normally
-
enabled by default when scheduling before register allocation, i.e.
with --ffsscchheedduullee--iinnssnnss or at --OO22 or higher.
-
--ffnnoo--sscchheedd--ssppeecc
Don't allow speculative motion of non-load instructions. This is normally
-
enabled by default when scheduling before register allocation, i.e.
with --ffsscchheedduullee--iinnssnnss or at --OO22 or higher.
-
--ffsscchheedd--ssppeecc--llooaadd
Allow speculative motion of some load instructions. This only makes
-
sense when scheduling before register allocation, i.e. with
--ffsscchheedduullee--iinnssnnss or at --OO22 or higher.
-
--ffsscchheedd--ssppeecc--llooaadd--ddaannggeerroouuss
Allow speculative motion of more load instructions. This only makes
-
sense when scheduling before register allocation, i.e. with
--ffsscchheedduullee--iinnssnnss or at --OO22 or higher.
-
--ffsscchheedd--ssttaalllleedd--iinnssnnss==_n
Define how many insns (if any) can be moved prematurely from the queue
-
of stalled insns into the ready list, during the second scheduling pass.
-
--ffsscchheedd--ssttaalllleedd--iinnssnnss--ddeepp==_n
Define how many insn groups (cycles) will be examined for a dependency
-
on a stalled insn that is candidate for premature removal from the queue
of stalled insns. Has an effect only during the second scheduling pass,
and only if --ffsscchheedd--ssttaalllleedd--iinnssnnss is used and its value is not zero.
-
--ffsscchheedd22--uussee--ssuuppeerrbblloocckkss
When scheduling after register allocation, do use superblock scheduling
-
algorithm. Superblock scheduling allows motion across basic block boundaries
resulting on faster schedules. This option is experimental, as not all machine
descriptions used by GCC model the CPU closely enough to avoid unreliable
results from the algorithm.
This only makes sense when scheduling after register allocation, i.e. with
--ffsscchheedduullee--iinnssnnss22 or at --OO22 or higher.
-
--ffsscchheedd22--uussee--ttrraacceess
Use --ffsscchheedd22--uussee--ssuuppeerrbblloocckkss algorithm when scheduling after register
-
allocation and additionally perform code duplication in order to increase the
size of superblocks using tracer pass. See --ffttrraacceerr for details on
trace formation.
This mode should produce faster but significantly longer programs. Also
without --ffbbrraanncchh--pprroobbaabbiilliittiieess the traces constructed may not
match the reality and hurt the performance. This only makes
sense when scheduling after register allocation, i.e. with
--ffsscchheedduullee--iinnssnnss22 or at --OO22 or higher.
-
--ffrreesscchheedduullee--mmoodduulloo--sscchheedduulleedd--llooooppss
The modulo scheduling comes before the traditional scheduling, if a loop was modulo scheduled
-
we may want to prevent the later scheduling passes from changing its schedule, we use this
option to control that.
-
--ffccaalllleerr--ssaavveess
Enable values to be allocated in registers that will be clobbered by
-
function calls, by emitting extra instructions to save and restore the
registers around such calls. Such allocation is done only when it
seems to result in better code than would otherwise be produced.
This option is always enabled by default on certain machines, usually
those which have no call-preserved registers to use instead.
Enabled at levels --OO22, --OO33, --OOss.
-
--ffttrreeee--pprree
Perform Partial Redundancy Elimination (PRE) on trees. This flag is
-
enabled by default at --OO22 and --OO33.
-
--ffttrreeee--ffrree
Perform Full Redundancy Elimination (FRE) on trees. The difference
-
between FRE and PRE is that FRE only considers expressions
that are computed on all paths leading to the redundant computation.
This analysis faster than PRE, though it exposes fewer redundancies.
This flag is enabled by default at --OO and higher.
-
--ffttrreeee--ccooppyy--pprroopp
Perform copy propagation on trees. This pass eliminates unnecessary
-
copy operations. This flag is enabled by default at --OO and
higher.
-
--ffttrreeee--ssttoorree--ccooppyy--pprroopp
Perform copy propagation of memory loads and stores. This pass
-
eliminates unnecessary copy operations in memory references
(structures, global variables, arrays, etc). This flag is enabled by
default at --OO22 and higher.
-
--ffttrreeee--ssaalliiaass
Perform structural alias analysis on trees. This flag
-
is enabled by default at --OO and higher.
-
--ffttrreeee--ssiinnkk
Perform forward store motion on trees. This flag is
-
enabled by default at --OO and higher.
-
--ffttrreeee--ccccpp
Perform sparse conditional constant propagation (CCP) on trees. This
-
pass only operates on local scalar variables and is enabled by default
at --OO and higher.
-
--ffttrreeee--ssttoorree--ccccpp
Perform sparse conditional constant propagation (CCP) on trees. This
-
pass operates on both local scalar variables and memory stores and
loads (global variables, structures, arrays, etc). This flag is
enabled by default at --OO22 and higher.
-
--ffttrreeee--ddccee
Perform dead code elimination (DCE) on trees. This flag is enabled by
-
default at --OO and higher.
-
--ffttrreeee--ddoommiinnaattoorr--ooppttss
Perform a variety of simple scalar cleanups (constant/copy
-
propagation, redundancy elimination, range propagation and expression
simplification) based on a dominator tree traversal. This also
performs jump threading (to reduce jumps to jumps). This flag is
enabled by default at --OO and higher.
-
--ffttrreeee--cchh
Perform loop header copying on trees. This is beneficial since it increases
-
effectiveness of code motion optimizations. It also saves one jump. This flag
is enabled by default at --OO and higher. It is not enabled
for --OOss, since it usually increases code size.
-
--ffttrreeee--lloooopp--ooppttiimmiizzee
Perform loop optimizations on trees. This flag is enabled by default
-
at --OO and higher.
-
--ffttrreeee--lloooopp--lliinneeaarr
Perform linear loop transformations on tree. This flag can improve cache
-
performance and allow further loop optimizations to take place.
-
--ffttrreeee--lloooopp--iimm
Perform loop invariant motion on trees. This pass moves only invariants that
-
would be hard to handle at RTL level (function calls, operations that expand to
nontrivial sequences of insns). With --ffuunnsswwiittcchh--llooooppss it also moves
operands of conditions that are invariant out of the loop, so that we can use
just trivial invariantness analysis in loop unswitching. The pass also includes
store motion.
-
--ffttrreeee--lloooopp--iivvccaannoonn
Create a canonical counter for number of iterations in the loop for that
-
determining number of iterations requires complicated analysis. Later
optimizations then may determine the number easily. Useful especially
in connection with unrolling.
-
--ffiivvooppttss
Perform induction variable optimizations (strength reduction, induction
-
variable merging and induction variable elimination) on trees.
-
--ffttrreeee--ssrraa
Perform scalar replacement of aggregates. This pass replaces structure
-
references with scalars to prevent committing structures to memory too
early. This flag is enabled by default at --OO and higher.
-
--ffttrreeee--ccooppyyrreennaammee
Perform copy renaming on trees. This pass attempts to rename compiler
-
temporaries to other variables at copy locations, usually resulting in
variable names which more closely resemble the original variables. This flag
is enabled by default at --OO and higher.
-
--ffttrreeee--tteerr
Perform temporary expression replacement during the SSA->normal phase. Single
-
use/single def temporaries are replaced at their use location with their
defining expression. This results in non-GIMPLE code, but gives the expanders
much more complex trees to work on resulting in better RTL generation. This is
enabled by default at --OO and higher.
-
--ffttrreeee--llrrss
Perform live range splitting during the SSA->normal phase. Distinct live
-
ranges of a variable are split into unique variables, allowing for better
optimization later. This is enabled by default at --OO and higher.
-
--ffttrreeee--vveeccttoorriizzee
Perform loop vectorization on trees.
-
-
--ffttrreeee--vveecctt--lloooopp--vveerrssiioonn
Perform loop versioning when doing loop vectorization on trees. When a loop
-
appears to be vectorizable except that data alignment or data dependence cannot
be determined at compile time then vectorized and non-vectorized versions of
the loop are generated along with runtime checks for alignment or dependence
to control which version is executed. This option is enabled by default
except at level --OOss where it is disabled.
-
--ffttrreeee--vvrrpp
Perform Value Range Propagation on trees. This is similar to the
-
constant propagation pass, but instead of values, ranges of values are
propagated. This allows the optimizers to remove unnecessary range
checks like array bound checks and null pointer checks. This is
enabled by default at --OO22 and higher. Null pointer check
elimination is only done if --ffddeelleettee--nnuullll--ppooiinntteerr--cchheecckkss is
enabled.
-
--ffttrraacceerr
Perform tail duplication to enlarge superblock size. This transformation
-
simplifies the control flow of the function allowing other optimizations to do
better job.
-
--ffuunnrroollll--llooooppss
Unroll loops whose number of iterations can be determined at compile
-
time or upon entry to the loop. --ffuunnrroollll--llooooppss implies both
--ffssttrreennggtthh--rreedduuccee and --ffrreerruunn--ccssee--aafftteerr--lloooopp. This
option makes code larger, and may or may not make it run faster.
-
--ffuunnrroollll--aallll--llooooppss
Unroll all loops, even if their number of iterations is uncertain when
-
the loop is entered. This usually makes programs run more slowly.
--ffuunnrroollll--aallll--llooooppss implies the same options as
--ffuunnrroollll--llooooppss,
-
--ffsspplliitt--iivvss--iinn--uunnrroolllleerr
Enables expressing of values of induction variables in later iterations
-
of the unrolled loop using the value in the first iteration. This breaks
long dependency chains, thus improving efficiency of the scheduling passes.
Combination of --ffwweebb and CSE is often sufficient to obtain the
same effect. However in cases the loop body is more complicated than
a single basic block, this is not reliable. It also does not work at all
on some of the architectures due to restrictions in the CSE pass.
This optimization is enabled by default.
-
--ffvvaarriiaabbllee--eexxppaannssiioonn--iinn--uunnrroolllleerr
With this option, the compiler will create multiple copies of some
-
local variables when unrolling a loop which can result in superior code.
-
--ffpprreeffeettcchh--lloooopp--aarrrraayyss
If supported by the target machine, generate instructions to prefetch
-
memory to improve the performance of loops that access large arrays.
These options may generate better or worse code; results are highly
dependent on the structure of loops within the source code.
-
--ffnnoo--ppeeeepphhoollee
-
-
--ffnnoo--ppeeeepphhoollee22
Disable any machine-specific peephole optimizations. The difference
-
between --ffnnoo--ppeeeepphhoollee and --ffnnoo--ppeeeepphhoollee22 is in how they
are implemented in the compiler; some targets use one, some use the
other, a few use both.
--ffppeeeepphhoollee is enabled by default.
--ffppeeeepphhoollee22 enabled at levels --OO22, --OO33, --OOss.
-
--ffnnoo--gguueessss--bbrraanncchh--pprroobbaabbiilliittyy
Do not guess branch probabilities using heuristics.
-
GCC will use heuristics to guess branch probabilities if they are
not provided by profiling feedback (--ffpprrooffiillee--aarrccss). These
heuristics are based on the control flow graph. If some branch probabilities
are specified by ____bbuuiillttiinn__eexxppeecctt, then the heuristics will be
used to guess branch probabilities for the rest of the control flow graph,
taking the ____bbuuiillttiinn__eexxppeecctt info into account. The interactions
between the heuristics and ____bbuuiillttiinn__eexxppeecctt can be complex, and in
some cases, it may be useful to disable the heuristics so that the effects
of ____bbuuiillttiinn__eexxppeecctt are easier to understand.
The default is --ffgguueessss--bbrraanncchh--pprroobbaabbiilliittyy at levels
--OO, --OO22, --OO33, --OOss.
-
--ffrreeoorrddeerr--bblloocckkss
Reorder basic blocks in the compiled function in order to reduce number of
-
taken branches and improve code locality.
Enabled at levels --OO22, --OO33.
-
--ffrreeoorrddeerr--bblloocckkss--aanndd--ppaarrttiittiioonn
In addition to reordering basic blocks in the compiled function, in order
-
to reduce number of taken branches, partitions hot and cold basic blocks
into separate sections of the assembly and .o files, to improve
paging and cache locality performance.
This optimization is automatically turned off in the presence of
exception handling, for linkonce sections, for functions with a user-defined
section attribute and on any architecture that does not support named
sections.
-
--ffrreeoorrddeerr--ffuunnccttiioonnss
Reorder functions in the object file in order to
-
improve code locality. This is implemented by using special
subsections ".text.hot" for most frequently executed functions and
".text.unlikely" for unlikely executed functions. Reordering is done by
the linker so object file format must support named sections and linker must
place them in a reasonable way.
Also profile feedback must be available in to make this option effective. See
--ffpprrooffiillee--aarrccss for details.
Enabled at levels --OO22, --OO33, --OOss.
-
--ffssttrriicctt--aalliiaassiinngg
Allows the compiler to assume the strictest aliasing rules applicable to
-
the language being compiled. For C (and C++), this activates
optimizations based on the type of expressions. In particular, an
object of one type is assumed never to reside at the same address as an
object of a different type, unless the types are almost the same. For
example, an "unsigned int" can alias an "int", but not a
"void*" or a "double". A character type may alias any other
type.
Pay special attention to code like this:
union a_union {
int i;
double d;
};
int f() {
a_union t;
t.d = 3.0;
return t.i;
}
The practice of reading from a different union member than the one most
recently written to (called "type-punning") is common. Even with
--ffssttrriicctt--aalliiaassiinngg, type-punning is allowed, provided the memory
is accessed through the union type. So, the code above will work as
expected. However, this code might not:
int f() {
a_union t;
int* ip;
t.d = 3.0;
ip = &t.i;
return *ip;
}
Every language that wishes to perform language-specific alias analysis
should define a function that computes, given an "tree"
node, an alias set for the node. Nodes in different alias sets are not
allowed to alias. For an example, see the C front-end function
"c_get_alias_set".
Enabled at levels --OO22, --OO33, --OOss.
-
--ffaalliiggnn--ffuunnccttiioonnss
-
-
--ffaalliiggnn--ffuunnccttiioonnss==_n
Align the start of functions to the next power-of-two greater than
-
_n, skipping up to _n bytes. For instance,
--ffaalliiggnn--ffuunnccttiioonnss==3322 aligns functions to the next 32-byte
boundary, but --ffaalliiggnn--ffuunnccttiioonnss==2244 would align to the next
32-byte boundary only if this can be done by skipping 23 bytes or less.
--ffnnoo--aalliiggnn--ffuunnccttiioonnss and --ffaalliiggnn--ffuunnccttiioonnss==11 are
equivalent and mean that functions will not be aligned.
Some assemblers only support this flag when _n is a power of two;
in that case, it is rounded up.
If _n is not specified or is zero, use a machine-dependent default.
Enabled at levels --OO22, --OO33.
-
--ffaalliiggnn--llaabbeellss
-
-
--ffaalliiggnn--llaabbeellss==_n
Align all branch targets to a power-of-two boundary, skipping up to
-
_n bytes like --ffaalliiggnn--ffuunnccttiioonnss. This option can easily
make code slower, because it must insert dummy operations for when the
branch target is reached in the usual flow of the code.
--ffnnoo--aalliiggnn--llaabbeellss and --ffaalliiggnn--llaabbeellss==11 are
equivalent and mean that labels will not be aligned.
If --ffaalliiggnn--llooooppss or --ffaalliiggnn--jjuummppss are applicable and
are greater than this value, then their values are used instead.
If _n is not specified or is zero, use a machine-dependent default
which is very likely to be 11, meaning no alignment.
Enabled at levels --OO22, --OO33.
-
--ffaalliiggnn--llooooppss
-
-
--ffaalliiggnn--llooooppss==_n
Align loops to a power-of-two boundary, skipping up to _n bytes
-
like --ffaalliiggnn--ffuunnccttiioonnss. The hope is that the loop will be
executed many times, which will make up for any execution of the dummy
operations.
--ffnnoo--aalliiggnn--llooooppss and --ffaalliiggnn--llooooppss==11 are
equivalent and mean that loops will not be aligned.
If _n is not specified or is zero, use a machine-dependent default.
Enabled at levels --OO22, --OO33.
-
--ffaalliiggnn--jjuummppss
-
-
--ffaalliiggnn--jjuummppss==_n
Align branch targets to a power-of-two boundary, for branch targets
-
where the targets can only be reached by jumping, skipping up to _n
bytes like --ffaalliiggnn--ffuunnccttiioonnss. In this case, no dummy operations
need be executed.
--ffnnoo--aalliiggnn--jjuummppss and --ffaalliiggnn--jjuummppss==11 are
equivalent and mean that loops will not be aligned.
If _n is not specified or is zero, use a machine-dependent default.
Enabled at levels --OO22, --OO33.
-
--ffuunniitt--aatt--aa--ttiimmee
Parse the whole compilation unit before starting to produce code.
-
This allows some extra optimizations to take place but consumes
more memory (in general). There are some compatibility issues
with _u_n_i_t_-_a_t_-_a_t_-_t_i_m_e mode:
-
*
enabling _u_n_i_t_-_a_t_-_a_-_t_i_m_e mode may change the order
-
in which functions, variables, and top-level "asm" statements
are emitted, and will likely break code relying on some particular
ordering. The majority of such top-level "asm" statements,
though, can be replaced by "section" attributes.
-
*
_u_n_i_t_-_a_t_-_a_-_t_i_m_e mode removes unreferenced static variables
-
and functions. This may result in undefined references
when an "asm" statement refers directly to variables or functions
that are otherwise unused. In that case either the variable/function
shall be listed as an operand of the "asm" statement operand or,
in the case of top-level "asm" statements the attribute "used"
shall be used on the declaration.
-
*
Static functions now can use non-standard passing conventions that
-
may break "asm" statements calling functions directly. Again,
attribute "used" will prevent this behavior.
As a temporary workaround, --ffnnoo--uunniitt--aatt--aa--ttiimmee can be used,
but this scheme may not be supported by future releases of GCC.
Enabled at levels --OO22, --OO33.
-
--ffwweebb
Constructs webs as commonly used for register allocation purposes and assign
-
each web individual pseudo register. This allows the register allocation pass
to operate on pseudos directly, but also strengthens several other optimization
passes, such as CSE, loop optimizer and trivial dead code remover. It can,
however, make debugging impossible, since variables will no longer stay in a
"home register".
Enabled by default with --ffuunnrroollll--llooooppss.
-
--ffwwhhoollee--pprrooggrraamm
Assume that the current compilation unit represents whole program being
-
compiled. All public functions and variables with the exception of "main"
and those merged by attribute "externally_visible" become static functions
and in a affect gets more aggressively optimized by interprocedural optimizers.
While this option is equivalent to proper use of "static" keyword for
programs consisting of single file, in combination with option
----ccoommbbiinnee this flag can be used to compile most of smaller scale C
programs since the functions and variables become local for the whole combined
compilation unit, not for the single source file itself.
-
--ffnnoo--ccpprroopp--rreeggiisstteerrss
After register allocation and post-register allocation instruction splitting,
-
we perform a copy-propagation pass to try to reduce scheduling dependencies
and occasionally eliminate the copy.
Disabled at levels --OO, --OO22, --OO33, --OOss.
-
--ffpprrooffiillee--ggeenneerraattee
Enable options usually used for instrumenting application to produce
-
profile useful for later recompilation with profile feedback based
optimization. You must use --ffpprrooffiillee--ggeenneerraattee both when
compiling and when linking your program.
The following options are enabled: "-fprofile-arcs", "-fprofile-values", "-fvpt".
-
--ffpprrooffiillee--uussee
Enable profile feedback directed optimizations, and optimizations
-
generally profitable only with profile feedback available.
The following options are enabled: "-fbranch-probabilities", "-fvpt",
"-funroll-loops", "-fpeel-loops", "-ftracer",
"-fno-loop-optimize".
The following options control compiler behavior regarding floating
point arithmetic. These options trade off between speed and
correctness. All must be specifically enabled.
-
--ffffllooaatt--ssttoorree
Do not store floating point variables in registers, and inhibit other
-
options that might change whether a floating point value is taken from a
register or memory.
This option prevents undesirable excess precision on machines such as
the 68000 where the floating registers (of the 68881) keep more
precision than a "double" is supposed to have. Similarly for the
x86 architecture. For most programs, the excess precision does only
good, but a few programs rely on the precise definition of IEEE floating
point. Use --ffffllooaatt--ssttoorree for such programs, after modifying
them to store all pertinent intermediate computations into variables.
-
--ffffaasstt--mmaatthh
Sets --ffnnoo--mmaatthh--eerrrrnnoo, --ffuunnssaaffee--mmaatthh--ooppttiimmiizzaattiioonnss, --ffnnoo--ttrraappppiinngg--mmaatthh, --ffffiinniittee--mmaatthh--oonnllyy,
-
--ffnnoo--rroouunnddiinngg--mmaatthh, --ffnnoo--ssiiggnnaalliinngg--nnaannss
and ffccxx--lliimmiitteedd--rraannggee.
This option causes the preprocessor macro "__FAST_MATH__" to be defined.
This option should never be turned on by any --OO option since
it can result in incorrect output for programs which depend on
an exact implementation of IEEE or ISO rules/specifications for
math functions.
-
--ffnnoo--mmaatthh--eerrrrnnoo
Do not set ERRNO after calling math functions that are executed
-
with a single instruction, e.g., sqrt. A program that relies on
IEEE exceptions for math error handling may want to use this flag
for speed while maintaining IEEE arithmetic compatibility.
This option should never be turned on by any --OO option since
it can result in incorrect output for programs which depend on
an exact implementation of IEEE or ISO rules/specifications for
math functions.
The default is --ffmmaatthh--eerrrrnnoo.
On Darwin systems, the math library never sets "errno". There is therefore
no reason for the compiler to consider the possibility that it might,
and --ffnnoo--mmaatthh--eerrrrnnoo is the default.
-
--ffuunnssaaffee--mmaatthh--ooppttiimmiizzaattiioonnss
Allow optimizations for floating-point arithmetic that (a) assume
-
that arguments and results are valid and (b) may violate IEEE or
ANSI standards. When used at link-time, it may include libraries
or startup files that change the default FPU control word or other
similar optimizations.
This option should never be turned on by any --OO option since
it can result in incorrect output for programs which depend on
an exact implementation of IEEE or ISO rules/specifications for
math functions.
The default is --ffnnoo--uunnssaaffee--mmaatthh--ooppttiimmiizzaattiioonnss.
-
--ffffiinniittee--mmaatthh--oonnllyy
Allow optimizations for floating-point arithmetic that assume
-
that arguments and results are not NaNs or +-Infs.
This option should never be turned on by any --OO option since
it can result in incorrect output for programs which depend on
an exact implementation of IEEE or ISO rules/specifications.
The default is --ffnnoo--ffiinniittee--mmaatthh--oonnllyy.
-
--ffnnoo--ttrraappppiinngg--mmaatthh
Compile code assuming that floating-point operations cannot generate
-
user-visible traps. These traps include division by zero, overflow,
underflow, inexact result and invalid operation. This option implies
--ffnnoo--ssiiggnnaalliinngg--nnaannss. Setting this option may allow faster
code if one relies on "non-stop" IEEE arithmetic, for example.
This option should never be turned on by any --OO option since
it can result in incorrect output for programs which depend on
an exact implementation of IEEE or ISO rules/specifications for
math functions.
The default is --ffttrraappppiinngg--mmaatthh.
-
--ffrroouunnddiinngg--mmaatthh
Disable transformations and optimizations that assume default floating
-
point rounding behavior. This is round-to-zero for all floating point
to integer conversions, and round-to-nearest for all other arithmetic
truncations. This option should be specified for programs that change
the FP rounding mode dynamically, or that may be executed with a
non-default rounding mode. This option disables constant folding of
floating point expressions at compile-time (which may be affected by
rounding mode) and arithmetic transformations that are unsafe in the
presence of sign-dependent rounding modes.
The default is --ffnnoo--rroouunnddiinngg--mmaatthh.
This option is experimental and does not currently guarantee to
disable all GCC optimizations that are affected by rounding mode.
Future versions of GCC may provide finer control of this setting
using C99's "FENV_ACCESS" pragma. This command line option
will be used to specify the default state for "FENV_ACCESS".
-
--ffssiiggnnaalliinngg--nnaannss
Compile code assuming that IEEE signaling NaNs may generate user-visible
-
traps during floating-point operations. Setting this option disables
optimizations that may change the number of exceptions visible with
signaling NaNs. This option implies --ffttrraappppiinngg--mmaatthh.
This option causes the preprocessor macro "__SUPPORT_SNAN__" to
be defined.
The default is --ffnnoo--ssiiggnnaalliinngg--nnaannss.
This option is experimental and does not currently guarantee to
disable all GCC optimizations that affect signaling NaN behavior.
-
--ffssiinnggllee--pprreecciissiioonn--ccoonnssttaanntt
Treat floating point constant as single precision constant instead of
-
implicitly converting it to double precision constant.
-
--ffccxx--lliimmiitteedd--rraannggee
-
-
--ffnnoo--ccxx--lliimmiitteedd--rraannggee
When enabled, this option states that a range reduction step is not
-
needed when performing complex division. The default is
--ffnnoo--ccxx--lliimmiitteedd--rraannggee, but is enabled by --ffffaasstt--mmaatthh.
This option controls the default setting of the ISO C99
"CX_LIMITED_RANGE" pragma. Nevertheless, the option applies to
all languages.
The following options control optimizations that may improve
performance, but are not enabled by any --OO options. This
section includes experimental options that may produce broken code.
-
--ffbbrraanncchh--pprroobbaabbiilliittiieess
After running a program compiled with --ffpprrooffiillee--aarrccss, you can compile it a second time using
-
--ffbbrraanncchh--pprroobbaabbiilliittiieess, to improve optimizations based on
the number of times each branch was taken. When the program
compiled with --ffpprrooffiillee--aarrccss exits it saves arc execution
counts to a file called _s_o_u_r_c_e_n_a_m_e_._g_c_d_a for each source
file The information in this data file is very dependent on the
structure of the generated code, so you must use the same source code
and the same optimization options for both compilations.
With --ffbbrraanncchh--pprroobbaabbiilliittiieess, GCC puts a
RREEGG__BBRR__PPRROOBB note on each JJUUMMPP__IINNSSNN and CCAALLLL__IINNSSNN.
These can be used to improve optimization. Currently, they are only
used in one place: in _r_e_o_r_g_._c, instead of guessing which path a
branch is mostly to take, the RREEGG__BBRR__PPRROOBB values are used to
exactly determine which path is taken more often.
-
--ffpprrooffiillee--vvaalluueess
If combined with --ffpprrooffiillee--aarrccss, it adds code so that some
-
data about values of expressions in the program is gathered.
With --ffbbrraanncchh--pprroobbaabbiilliittiieess, it reads back the data gathered
from profiling values of expressions and adds RREEGG__VVAALLUUEE__PPRROOFFIILLEE
notes to instructions for their later usage in optimizations.
Enabled with --ffpprrooffiillee--ggeenneerraattee and --ffpprrooffiillee--uussee.
-
--ffvvpptt
If combined with --ffpprrooffiillee--aarrccss, it instructs the compiler to add
-
a code to gather information about values of expressions.
With --ffbbrraanncchh--pprroobbaabbiilliittiieess, it reads back the data gathered
and actually performs the optimizations based on them.
Currently the optimizations include specialization of division operation
using the knowledge about the value of the denominator.
-
--ffrreennaammee--rreeggiisstteerrss
Attempt to avoid false dependencies in scheduled code by making use
-
of registers left over after register allocation. This optimization
will most benefit processors with lots of registers. Depending on the
debug information format adopted by the target, however, it can
make debugging impossible, since variables will no longer stay in
a "home register".
Enabled by default with --ffuunnrroollll--llooooppss.
-
--ffttrraacceerr
Perform tail duplication to enlarge superblock size. This transformation
-
simplifies the control flow of the function allowing other optimizations to do
better job.
Enabled with --ffpprrooffiillee--uussee.
-
--ffuunnrroollll--llooooppss
Unroll loops whose number of iterations can be determined at compile time or
-
upon entry to the loop. --ffuunnrroollll--llooooppss implies
--ffrreerruunn--ccssee--aafftteerr--lloooopp, --ffwweebb and --ffrreennaammee--rreeggiisstteerrss.
It also turns on complete loop peeling (i.e. complete removal of loops with
small constant number of iterations). This option makes code larger, and may
or may not make it run faster.
Enabled with --ffpprrooffiillee--uussee.
-
--ffuunnrroollll--aallll--llooooppss
Unroll all loops, even if their number of iterations is uncertain when
-
the loop is entered. This usually makes programs run more slowly.
--ffuunnrroollll--aallll--llooooppss implies the same options as
--ffuunnrroollll--llooooppss.
-
--ffppeeeell--llooooppss
Peels the loops for that there is enough information that they do not
-
roll much (from profile feedback). It also turns on complete loop peeling
(i.e. complete removal of loops with small constant number of iterations).
Enabled with --ffpprrooffiillee--uussee.
-
--ffmmoovvee--lloooopp--iinnvvaarriiaannttss
Enables the loop invariant motion pass in the new loop optimizer. Enabled
-
at level --OO11
-
--ffuunnsswwiittcchh--llooooppss
Move branches with loop invariant conditions out of the loop, with duplicates
-
of the loop on both branches (modified according to result of the condition).
-
--ffpprreeffeettcchh--lloooopp--aarrrraayyss
If supported by the target machine, generate instructions to prefetch
-
memory to improve the performance of loops that access large arrays.
Disabled at level --OOss.
-
--ffffuunnccttiioonn--sseeccttiioonnss
-
-
--ffddaattaa--sseeccttiioonnss
Place each function or data item into its own section in the output
-
file if the target supports arbitrary sections. The name of the
function or the name of the data item determines the section's name
in the output file.
Use these options on systems where the linker can perform optimizations
to improve locality of reference in the instruction space. Most systems
using the ELF object format and SPARC processors running Solaris 2 have
linkers with such optimizations. AIX may have these optimizations in
the future.
Only use these options when there are significant benefits from doing
so. When you specify these options, the assembler and linker will
create larger object and executable files and will also be slower.
You will not be able to use "gprof" on all systems if you
specify this option and you may have problems with debugging if
you specify both this option and --gg.
-
--ffbbrraanncchh--ttaarrggeett--llooaadd--ooppttiimmiizzee
Perform branch target register load optimization before prologue / epilogue
-
threading.
The use of target registers can typically be exposed only during reload,
thus hoisting loads out of loops and doing inter-block scheduling needs
a separate optimization pass.
-
--ffbbrraanncchh--ttaarrggeett--llooaadd--ooppttiimmiizzee22
Perform branch target register load optimization after prologue / epilogue
-
threading.
-
--ffbbttrr--bbbb--eexxcclluussiivvee
When performing branch target register load optimization, don't reuse
-
branch target registers in within any basic block.
-
--ffssttaacckk--pprrootteeccttoorr
Emit extra code to check for buffer overflows, such as stack smashing
-
attacks. This is done by adding a guard variable to functions with
vulnerable objects. This includes functions that call alloca, and
functions with buffers larger than 8 bytes. The guards are initialized
when a function is entered and then checked when the function exits.
If a guard check fails, an error message is printed and the program exits.
-
--ffssttaacckk--pprrootteeccttoorr--aallll
Like --ffssttaacckk--pprrootteeccttoorr except that all functions are protected.
-
-
----ppaarraamm _n_a_m_e==_v_a_l_u_e
In some places, GCC uses various constants to control the amount of
-
optimization that is done. For example, GCC will not inline functions
that contain more that a certain number of instructions. You can
control some of these constants on the command-line using the
----ppaarraamm option.
The names of specific parameters, and the meaning of the values, are
tied to the internals of the compiler, and are subject to change
without notice in future releases.
In each case, the _v_a_l_u_e is an integer. The allowable choices for
_n_a_m_e are given in the following table:
-
ssaalliiaass--mmaaxx--iimmpplliicciitt--ffiieellddss
The maximum number of fields in a variable without direct
-
structure accesses for which structure aliasing will consider trying
to track each field. The default is 5
-
ssrraa--mmaaxx--ssttrruuccttuurree--ssiizzee
The maximum structure size, in bytes, at which the scalar replacement
-
of aggregates (SRA) optimization will perform block copies. The
default value, 0, implies that GCC will select the most appropriate
size itself.
-
ssrraa--ffiieelldd--ssttrruuccttuurree--rraattiioo
The threshold ratio (as a percentage) between instantiated fields and
-
the complete structure size. We say that if the ratio of the number
of bytes in instantiated fields to the number of bytes in the complete
structure exceeds this parameter, then block copies are not used. The
default is 75.
-
mmaaxx--ccrroossssjjuummpp--eeddggeess
The maximum number of incoming edges to consider for crossjumping.
-
The algorithm used by --ffccrroossssjjuummppiinngg is O(N^2) in
the number of edges incoming to each block. Increasing values mean
more aggressive optimization, making the compile time increase with
probably small improvement in executable size.
-
mmiinn--ccrroossssjjuummpp--iinnssnnss
The minimum number of instructions which must be matched at the end
-
of two blocks before crossjumping will be performed on them. This
value is ignored in the case where all instructions in the block being
crossjumped from are matched. The default value is 5.
-
mmaaxx--ggrrooww--ccooppyy--bbbb--iinnssnnss
The maximum code size expansion factor when copying basic blocks
-
instead of jumping. The expansion is relative to a jump instruction.
The default value is 8.
-
mmaaxx--ggoottoo--dduupplliiccaattiioonn--iinnssnnss
The maximum number of instructions to duplicate to a block that jumps
-
to a computed goto. To avoid O(N^2) behavior in a number of
passes, GCC factors computed gotos early in the compilation process,
and unfactors them as late as possible. Only computed jumps at the
end of a basic blocks with no more than max-goto-duplication-insns are
unfactored. The default value is 8.
-
mmaaxx--ddeellaayy--sslloott--iinnssnn--sseeaarrcchh
The maximum number of instructions to consider when looking for an
-
instruction to fill a delay slot. If more than this arbitrary number of
instructions is searched, the time savings from filling the delay slot
will be minimal so stop searching. Increasing values mean more
aggressive optimization, making the compile time increase with probably
small improvement in executable run time.
-
mmaaxx--ddeellaayy--sslloott--lliivvee--sseeaarrcchh
When trying to fill delay slots, the maximum number of instructions to
-
consider when searching for a block with valid live register
information. Increasing this arbitrarily chosen value means more
aggressive optimization, increasing the compile time. This parameter
should be removed when the delay slot code is rewritten to maintain the
control-flow graph.
-
mmaaxx--ggccssee--mmeemmoorryy
The approximate maximum amount of memory that will be allocated in
-
order to perform the global common subexpression elimination
optimization. If more memory than specified is required, the
optimization will not be done.
-
mmaaxx--ggccssee--ppaasssseess
The maximum number of passes of GCSE to run. The default is 1.
-
-
mmaaxx--ppeennddiinngg--lliisstt--lleennggtthh
The maximum number of pending dependencies scheduling will allow
-
before flushing the current state and starting over. Large functions
with few branches or calls can create excessively large lists which
needlessly consume memory and resources.
-
mmaaxx--iinnlliinnee--iinnssnnss--ssiinnggllee
Several parameters control the tree inliner used in gcc.
-
This number sets the maximum number of instructions (counted in GCC's
internal representation) in a single function that the tree inliner
will consider for inlining. This only affects functions declared
inline and methods implemented in a class declaration (C++).
The default value is 450.
-
mmaaxx--iinnlliinnee--iinnssnnss--aauuttoo
When you use --ffiinnlliinnee--ffuunnccttiioonnss (included in --OO33),
-
a lot of functions that would otherwise not be considered for inlining
by the compiler will be investigated. To those functions, a different
(more restrictive) limit compared to functions declared inline can
be applied.
The default value is 90.
-
llaarrggee--ffuunnccttiioonn--iinnssnnss
The limit specifying really large functions. For functions larger than this
-
limit after inlining inlining is constrained by
----ppaarraamm llaarrggee--ffuunnccttiioonn--ggrroowwtthh. This parameter is useful primarily
to avoid extreme compilation time caused by non-linear algorithms used by the
backend.
This parameter is ignored when --ffuunniitt--aatt--aa--ttiimmee is not used.
The default value is 2700.
-
llaarrggee--ffuunnccttiioonn--ggrroowwtthh
Specifies maximal growth of large function caused by inlining in percents.
-
This parameter is ignored when --ffuunniitt--aatt--aa--ttiimmee is not used.
The default value is 100 which limits large function growth to 2.0 times
the original size.
-
llaarrggee--uunniitt--iinnssnnss
The limit specifying large translation unit. Growth caused by inlining of
-
units larger than this limit is limited by ----ppaarraamm iinnlliinnee--uunniitt--ggrroowwtthh.
For small units this might be too tight (consider unit consisting of function A
that is inline and B that just calls A three time. If B is small relative to
A, the growth of unit is 300\% and yet such inlining is very sane. For very
large units consisting of small inlininable functions however the overall unit
growth limit is needed to avoid exponential explosion of code size. Thus for
smaller units, the size is increased to ----ppaarraamm llaarrggee--uunniitt--iinnssnnss
before aplying ----ppaarraamm iinnlliinnee--uunniitt--ggrroowwtthh. The default is 10000
-
iinnlliinnee--uunniitt--ggrroowwtthh
Specifies maximal overall growth of the compilation unit caused by inlining.
-
This parameter is ignored when --ffuunniitt--aatt--aa--ttiimmee is not used.
The default value is 50 which limits unit growth to 1.5 times the original
size.
-
mmaaxx--iinnlliinnee--iinnssnnss--rreeccuurrssiivvee
-
-
mmaaxx--iinnlliinnee--iinnssnnss--rreeccuurrssiivvee--aauuttoo
Specifies maximum number of instructions out-of-line copy of self recursive inline
-
function can grow into by performing recursive inlining.
For functions declared inline ----ppaarraamm mmaaxx--iinnlliinnee--iinnssnnss--rreeccuurrssiivvee is
taken into acount. For function not declared inline, recursive inlining
happens only when --ffiinnlliinnee--ffuunnccttiioonnss (included in --OO33) is
enabled and ----ppaarraamm mmaaxx--iinnlliinnee--iinnssnnss--rreeccuurrssiivvee--aauuttoo is used. The
default value is 450.
-
mmaaxx--iinnlliinnee--rreeccuurrssiivvee--ddeepptthh
-
-
mmaaxx--iinnlliinnee--rreeccuurrssiivvee--ddeepptthh--aauuttoo
Specifies maximum recursion depth used by the recursive inlining.
-
For functions declared inline ----ppaarraamm mmaaxx--iinnlliinnee--rreeccuurrssiivvee--ddeepptthh is
taken into acount. For function not declared inline, recursive inlining
happens only when --ffiinnlliinnee--ffuunnccttiioonnss (included in --OO33) is
enabled and ----ppaarraamm mmaaxx--iinnlliinnee--rreeccuurrssiivvee--ddeepptthh--aauuttoo is used. The
default value is 450.
-
mmiinn--iinnlliinnee--rreeccuurrssiivvee--pprroobbaabbiilliittyy
Recursive inlining is profitable only for function having deep recursion
-
in average and can hurt for function having little recursion depth by
increasing the prologue size or complexity of function body to other
optimizers.
When profile feedback is available (see --ffpprrooffiillee--ggeenneerraattee) the actual
recursion depth can be guessed from probability that function will recurse via
given call expression. This parameter limits inlining only to call expression
whose probability exceeds given threshold (in percents). The default value is
10.
-
iinnlliinnee--ccaallll--ccoosstt
Specify cost of call instruction relative to simple arithmetics operations
-
(having cost of 1). Increasing this cost disqualifies inlining of non-leaf
functions and at the same time increases size of leaf function that is believed to
reduce function size by being inlined. In effect it increases amount of
inlining for code having large abstraction penalty (many functions that just
pass the arguments to other functions) and decrease inlining for code with low
abstraction penalty. The default value is 16.
-
mmaaxx--uunnrroolllleedd--iinnssnnss
The maximum number of instructions that a loop should have if that loop
-
is unrolled, and if the loop is unrolled, it determines how many times
the loop code is unrolled.
-
mmaaxx--aavveerraaggee--uunnrroolllleedd--iinnssnnss
The maximum number of instructions biased by probabilities of their execution
-
that a loop should have if that loop is unrolled, and if the loop is unrolled,
it determines how many times the loop code is unrolled.
-
mmaaxx--uunnrroollll--ttiimmeess
The maximum number of unrollings of a single loop.
-
-
mmaaxx--ppeeeelleedd--iinnssnnss
The maximum number of instructions that a loop should have if that loop
-
is peeled, and if the loop is peeled, it determines how many times
the loop code is peeled.
-
mmaaxx--ppeeeell--ttiimmeess
The maximum number of peelings of a single loop.
-
-
mmaaxx--ccoommpplleetteellyy--ppeeeelleedd--iinnssnnss
The maximum number of insns of a completely peeled loop.
-
-
mmaaxx--ccoommpplleetteellyy--ppeeeell--ttiimmeess
The maximum number of iterations of a loop to be suitable for complete peeling.
-
-
mmaaxx--uunnsswwiittcchh--iinnssnnss
The maximum number of insns of an unswitched loop.
-
-
mmaaxx--uunnsswwiittcchh--lleevveell
The maximum number of branches unswitched in a single loop.
-
-
lliimm--eexxppeennssiivvee
The minimum cost of an expensive expression in the loop invariant motion.
-
-
iivv--ccoonnssiiddeerr--aallll--ccaannddiiddaatteess--bboouunndd
Bound on number of candidates for induction variables below that
-
all candidates are considered for each use in induction variable
optimizations. Only the most relevant candidates are considered
if there are more candidates, to avoid quadratic time complexity.
-
iivv--mmaaxx--ccoonnssiiddeerreedd--uusseess
The induction variable optimizations give up on loops that contain more
-
induction variable uses.
-
iivv--aallwwaayyss--pprruunnee--ccaanndd--sseett--bboouunndd
If number of candidates in the set is smaller than this value,
-
we always try to remove unnecessary ivs from the set during its
optimization when a new iv is added to the set.
-
sscceevv--mmaaxx--eexxpprr--ssiizzee
Bound on size of expressions used in the scalar evolutions analyzer.
-
Large expressions slow the analyzer.
-
vveecctt--mmaaxx--vveerrssiioonn--cchheecckkss
The maximum number of runtime checks that can be performed when doing
-
loop versioning in the vectorizer. See option ftree-vect-loop-version
for more information.
-
mmaaxx--iitteerraattiioonnss--ttoo--ttrraacckk
The maximum number of iterations of a loop the brute force algorithm
-
for analysis of # of iterations of the loop tries to evaluate.
-
hhoott--bbbb--ccoouunntt--ffrraaccttiioonn
Select fraction of the maximal count of repetitions of basic block in program
-
given basic block needs to have to be considered hot.
-
hhoott--bbbb--ffrreeqquueennccyy--ffrraaccttiioonn
Select fraction of the maximal frequency of executions of basic block in
-
function given basic block needs to have to be considered hot
-
mmaaxx--pprreeddiicctteedd--iitteerraattiioonnss
The maximum number of loop iterations we predict statically. This is useful
-
in cases where function contain single loop with known bound and other loop
with unknown. We predict the known number of iterations correctly, while
the unknown number of iterations average to roughly 10. This means that the
loop without bounds would appear artificially cold relative to the other one.
-
ttrraacceerr--ddyynnaammiicc--ccoovveerraaggee
-
-
ttrraacceerr--ddyynnaammiicc--ccoovveerraaggee--ffeeeeddbbaacckk
This value is used to limit superblock formation once the given percentage of
-
executed instructions is covered. This limits unnecessary code size
expansion.
The ttrraacceerr--ddyynnaammiicc--ccoovveerraaggee--ffeeeeddbbaacckk is used only when profile
feedback is available. The real profiles (as opposed to statically estimated
ones) are much less balanced allowing the threshold to be larger value.
-
ttrraacceerr--mmaaxx--ccooddee--ggrroowwtthh
Stop tail duplication once code growth has reached given percentage. This is
-
rather hokey argument, as most of the duplicates will be eliminated later in
cross jumping, so it may be set to much higher values than is the desired code
growth.
-
ttrraacceerr--mmiinn--bbrraanncchh--rraattiioo
Stop reverse growth when the reverse probability of best edge is less than this
-
threshold (in percent).
-
ttrraacceerr--mmiinn--bbrraanncchh--rraattiioo
-
-
ttrraacceerr--mmiinn--bbrraanncchh--rraattiioo--ffeeeeddbbaacckk
Stop forward growth if the best edge do have probability lower than this
-
threshold.
Similarly to ttrraacceerr--ddyynnaammiicc--ccoovveerraaggee two values are present, one for
compilation for profile feedback and one for compilation without. The value
for compilation with profile feedback needs to be more conservative (higher) in
order to make tracer effective.
-
mmaaxx--ccssee--ppaatthh--lleennggtthh
Maximum number of basic blocks on path that cse considers. The default is 10.
-
-
mmaaxx--ccssee--iinnssnnss
The maximum instructions CSE process before flushing. The default is 1000.
-
-
gglloobbaall--vvaarr--tthhrreesshhoolldd
Counts the number of function calls (_n) and the number of
-
call-clobbered variables (_v). If _nx_v is larger than this limit, a
single artificial variable will be created to represent all the
call-clobbered variables at function call sites. This artificial
variable will then be made to alias every call-clobbered variable.
(done as "int * size_t" on the host machine; beware overflow).
-
mmaaxx--aalliiaasseedd--vvooppss
Maximum number of virtual operands allowed to represent aliases
-
before triggering the alias grouping heuristic. Alias grouping
reduces compile times and memory consumption needed for aliasing at
the expense of precision loss in alias information.
-
ggggcc--mmiinn--eexxppaanndd
GCC uses a garbage collector to manage its own memory allocation. This
-
parameter specifies the minimum percentage by which the garbage
collector's heap should be allowed to expand between collections.
Tuning this may improve compilation speed; it has no effect on code
generation.
The default is 30% + 70% * (RAM/1GB) with an upper bound of 100% when
RAM >= 1GB. If "getrlimit" is available, the notion of "RAM" is
the smallest of actual RAM and "RLIMIT_DATA" or "RLIMIT_AS". If
GCC is not able to calculate RAM on a particular platform, the lower
bound of 30% is used. Setting this parameter and
ggggcc--mmiinn--hheeaappssiizzee to zero causes a full collection to occur at
every opportunity. This is extremely slow, but can be useful for
debugging.
-
ggggcc--mmiinn--hheeaappssiizzee
Minimum size of the garbage collector's heap before it begins bothering
-
to collect garbage. The first collection occurs after the heap expands
by ggggcc--mmiinn--eexxppaanndd% beyond ggggcc--mmiinn--hheeaappssiizzee. Again,
tuning this may improve compilation speed, and has no effect on code
generation.
The default is the smaller of RAM/8, RLIMIT_RSS, or a limit which
tries to ensure that RLIMIT_DATA or RLIMIT_AS are not exceeded, but
with a lower bound of 4096 (four megabytes) and an upper bound of
131072 (128 megabytes). If GCC is not able to calculate RAM on a
particular platform, the lower bound is used. Setting this parameter
very large effectively disables garbage collection. Setting this
parameter and ggggcc--mmiinn--eexxppaanndd to zero causes a full collection
to occur at every opportunity.
-
mmaaxx--rreellooaadd--sseeaarrcchh--iinnssnnss
The maximum number of instruction reload should look backward for equivalent
-
register. Increasing values mean more aggressive optimization, making the
compile time increase with probably slightly better performance. The default
value is 100.
-
mmaaxx--ccsseelliibb--mmeemmoorryy--llooccaattiioonn
The maximum number of memory locations cselib should take into acount.
-
Increasing values mean more aggressive optimization, making the compile time
increase with probably slightly better performance. The default value is 500.
-
mmaaxx--ffllooww--mmeemmoorryy--llooccaattiioonn
Similar as mmaaxx--ccsseelliibb--mmeemmoorryy--llooccaattiioonn but for dataflow liveness.
-
The default value is 100.
-
rreeoorrddeerr--bblloocckkss--dduupplliiccaattee
-
-
rreeoorrddeerr--bblloocckkss--dduupplliiccaattee--ffeeeeddbbaacckk
Used by basic block reordering pass to decide whether to use unconditional
-
branch or duplicate the code on its destination. Code is duplicated when its
estimated size is smaller than this value multiplied by the estimated size of
unconditional jump in the hot spots of the program.
The rreeoorrddeerr--bblloocckk--dduupplliiccaattee--ffeeeeddbbaacckk is used only when profile
feedback is available and may be set to higher values than
rreeoorrddeerr--bblloocckk--dduupplliiccaattee since information about the hot spots is more
accurate.
-
mmaaxx--sscchheedd--rreeggiioonn--bblloocckkss
The maximum number of blocks in a region to be considered for
-
interblock scheduling. The default value is 10.
-
mmaaxx--sscchheedd--rreeggiioonn--iinnssnnss
The maximum number of insns in a region to be considered for
-
interblock scheduling. The default value is 100.
-
mmiinn--sscchheedd--pprroobb
The minimum probability of reaching a source block for interblock
-
speculative scheduling. The default value is 40.
-
mmaaxx--llaasstt--vvaalluuee--rrttll
The maximum size measured as number of RTLs that can be recorded in an expression
-
in combiner for a pseudo register as last known value of that register. The default
is 10000.
-
iinntteeggeerr--sshhaarree--lliimmiitt
Small integer constants can use a shared data structure, reducing the
-
compiler's memory usage and increasing its speed. This sets the maximum
value of a shared integer constant's. The default value is 256.
-
mmiinn--vviirrttuuaall--mmaappppiinnggss
Specifies the minimum number of virtual mappings in the incremental
-
SSA updater that should be registered to trigger the virtual mappings
heuristic defined by virtual-mappings-ratio. The default value is
100.
-
vviirrttuuaall--mmaappppiinnggss--rraattiioo
If the number of virtual mappings is virtual-mappings-ratio bigger
-
than the number of virtual symbols to be updated, then the incremental
SSA updater switches to a full update for those symbols. The default
ratio is 3.
-
sssspp--bbuuffffeerr--ssiizzee
The minimum size of buffers (i.e. arrays) that will receive stack smashing
-
protection when --ffssttaacckk--pprrootteeccttiioonn is used.
-
mmaaxx--jjuummpp--tthhrreeaadd--dduupplliiccaattiioonn--ssttmmttss
Maximum number of statements allowed in a block that needs to be
-
duplicated when threading jumps.
-
mmaaxx--ffiieellddss--ffoorr--ffiieelldd--sseennssiittiivvee
Maximum number of fields in a structure we will treat in
-
a field sensitive manner during pointer analysis.
OOppttiioonnss CCoonnttrroolllliinngg tthhee PPrreepprroocceessssoorr
These options control the C preprocessor, which is run on each C source
file before actual compilation.
If you use the --EE option, nothing is done except preprocessing.
Some of these options make sense only together with --EE because
they cause the preprocessor output to be unsuitable for actual
compilation.
You can use --WWpp,,_o_p_t_i_o_n to bypass the compiler driver
and pass _o_p_t_i_o_n directly through to the preprocessor. If
_o_p_t_i_o_n contains commas, it is split into multiple options at the
commas. However, many options are modified, translated or interpreted
by the compiler driver before being passed to the preprocessor, and
--WWpp forcibly bypasses this phase. The preprocessor's direct
interface is undocumented and subject to change, so whenever possible
you should avoid using --WWpp and let the driver handle the
options instead.
-
--XXpprreepprroocceessssoorr _o_p_t_i_o_n
Pass _o_p_t_i_o_n as an option to the preprocessor. You can use this to
-
supply system-specific preprocessor options which GCC does not know how to
recognize.
If you want to pass an option that takes an argument, you must use
--XXpprreepprroocceessssoorr twice, once for the option and once for the argument.
-
--DD _n_a_m_e
Predefine _n_a_m_e as a macro, with definition 1.
-
-
--DD _n_a_m_e==_d_e_f_i_n_i_t_i_o_n
The contents of _d_e_f_i_n_i_t_i_o_n are tokenized and processed as if
-
they appeared during translation phase three in a ##ddeeffiinnee
directive. In particular, the definition will be truncated by
embedded newline characters.
If you are invoking the preprocessor from a shell or shell-like
program you may need to use the shell's quoting syntax to protect
characters such as spaces that have a meaning in the shell syntax.
If you wish to define a function-like macro on the command line, write
its argument list with surrounding parentheses before the equals sign
(if any). Parentheses are meaningful to most shells, so you will need
to quote the option. With sshh and ccsshh,
--DD''_n_a_m_e((_a_r_g_s_._._.))==_d_e_f_i_n_i_t_i_o_n'' works.
--DD and --UU options are processed in the order they
are given on the command line. All --iimmaaccrrooss _f_i_l_e and
--iinncclluuddee _f_i_l_e options are processed after all
--DD and --UU options.
-
--UU _n_a_m_e
Cancel any previous definition of _n_a_m_e, either built in or
-
provided with a --DD option.
-
--uunnddeeff
Do not predefine any system-specific or GCC-specific macros. The
-
standard predefined macros remain defined.
-
--II _d_i_r
Add the directory _d_i_r to the list of directories to be searched
-
for header files.
Directories named by --II are searched before the standard
system include directories. If the directory _d_i_r is a standard
system include directory, the option is ignored to ensure that the
default search order for system directories and the special treatment
of system headers are not defeated
.
-
--oo _f_i_l_e
Write output to _f_i_l_e. This is the same as specifying _f_i_l_e
-
as the second non-option argument to ccpppp. ggcccc has a
different interpretation of a second non-option argument, so you must
use --oo to specify the output file.
-
--WWaallll
Turns on all optional warnings which are desirable for normal code.
-
At present this is --WWccoommmmeenntt, --WWttrriiggrraapphhss,
--WWmmuullttiicchhaarr and a warning about integer promotion causing a
change of sign in "#if" expressions. Note that many of the
preprocessor's warnings are on by default and have no options to
control them.
-
--WWccoommmmeenntt
-
-
--WWccoommmmeennttss
Warn whenever a comment-start sequence //** appears in a //**
-
comment, or whenever a backslash-newline appears in a //// comment.
(Both forms have the same effect.)
-
--WWttrriiggrraapphhss
@anchor{Wtrigraphs}
-
Most trigraphs in comments cannot affect the meaning of the program.
However, a trigraph that would form an escaped newline (????// at
the end of a line) can, by changing where the comment begins or ends.
Therefore, only trigraphs that would form escaped newlines produce
warnings inside a comment.
This option is implied by --WWaallll. If --WWaallll is not
given, this option is still enabled unless trigraphs are enabled. To
get trigraph conversion without warnings, but get the other
--WWaallll warnings, use --ttrriiggrraapphhss --WWaallll --WWnnoo--ttrriiggrraapphhss.
-
--WWttrraaddiittiioonnaall
Warn about certain constructs that behave differently in traditional and
-
ISO C. Also warn about ISO C constructs that have no traditional C
equivalent, and problematic constructs which should be avoided.
-
--WWiimmppoorrtt
Warn the first time ##iimmppoorrtt is used.
-
-
--WWuunnddeeff
Warn whenever an identifier which is not a macro is encountered in an
-
##iiff directive, outside of ddeeffiinneedd. Such identifiers are
replaced with zero.
-
--WWuunnuusseedd--mmaaccrrooss
Warn about macros defined in the main file that are unused. A macro
-
is _u_s_e_d if it is expanded or tested for existence at least once.
The preprocessor will also warn if the macro has not been used at the
time it is redefined or undefined.
Built-in macros, macros defined on the command line, and macros
defined in include files are not warned about.
_N_o_t_e_: If a macro is actually used, but only used in skipped
conditional blocks, then CPP will report it as unused. To avoid the
warning in such a case, you might improve the scope of the macro's
definition by, for example, moving it into the first skipped block.
Alternatively, you could provide a dummy use with something like:
#if defined the_macro_causing_the_warning
#endif
-
--WWeennddiiff--llaabbeellss
Warn whenever an ##eellssee or an ##eennddiiff are followed by text.
-
This usually happens in code of the form
#if FOO
...
#else FOO
...
#endif FOO
The second and third "FOO" should be in comments, but often are not
in older programs. This warning is on by default.
-
--WWeerrrroorr
Make all warnings into hard errors. Source code which triggers warnings
-
will be rejected.
-
--WWssyysstteemm--hheeaaddeerrss
Issue warnings for code in system headers. These are normally unhelpful
-
in finding bugs in your own code, therefore suppressed. If you are
responsible for the system library, you may want to see them.
-
--ww
Suppress all warnings, including those which GNU CPP issues by default.
-
-
--ppeeddaannttiicc
Issue all the mandatory diagnostics listed in the C standard. Some of
-
them are left out by default, since they trigger frequently on harmless
code.
-
--ppeeddaannttiicc--eerrrroorrss
Issue all the mandatory diagnostics, and make all mandatory diagnostics
-
into errors. This includes mandatory diagnostics that GCC issues
without --ppeeddaannttiicc but treats as warnings.
-
--MM
Instead of outputting the result of preprocessing, output a rule
-
suitable for mmaakkee describing the dependencies of the main
source file. The preprocessor outputs one mmaakkee rule containing
the object file name for that source file, a colon, and the names of all
the included files, including those coming from --iinncclluuddee or
--iimmaaccrrooss command line options.
Unless specified explicitly (with --MMTT or --MMQQ), the
object file name consists of the basename of the source file with any
suffix replaced with object file suffix. If there are many included
files then the rule is split into several lines using \\-newline.
The rule has no commands.
This option does not suppress the preprocessor's debug output, such as
--ddMM. To avoid mixing such debug output with the dependency
rules you should explicitly specify the dependency output file with
--MMFF, or use an environment variable like
DDEEPPEENNDDEENNCCIIEESS__OOUUTTPPUUTT. Debug output
will still be sent to the regular output stream as normal.
Passing --MM to the driver implies --EE, and suppresses
warnings with an implicit --ww.
-
--MMMM
Like --MM but do not mention header files that are found in
-
system header directories, nor header files that are included,
directly or indirectly, from such a header.
This implies that the choice of angle brackets or double quotes in an
##iinncclluuddee directive does not in itself determine whether that
header will appear in --MMMM dependency output. This is a
slight change in semantics from GCC versions 3.0 and earlier.
@anchor{dashMF}
-
--MMFF _f_i_l_e
When used with --MM or --MMMM, specifies a
-
file to write the dependencies to. If no --MMFF switch is given
the preprocessor sends the rules to the same place it would have sent
preprocessed output.
When used with the driver options --MMDD or --MMMMDD,
--MMFF overrides the default dependency output file.
-
--MMGG
In conjunction with an option such as --MM requesting
-
dependency generation, --MMGG assumes missing header files are
generated files and adds them to the dependency list without raising
an error. The dependency filename is taken directly from the
"#include" directive without prepending any path. --MMGG
also suppresses preprocessed output, as a missing header file renders
this useless.
This feature is used in automatic updating of makefiles.
-
--MMPP
This option instructs CPP to add a phony target for each dependency
-
other than the main file, causing each to depend on nothing. These
dummy rules work around errors mmaakkee gives if you remove header
files without updating the _M_a_k_e_f_i_l_e to match.
This is typical output:
test.o: test.c test.h
test.h:
-
--MMTT _t_a_r_g_e_t
Change the target of the rule emitted by dependency generation. By
-
default CPP takes the name of the main input file, including any path,
deletes any file suffix such as ..cc, and appends the platform's
usual object suffix. The result is the target.
An --MMTT option will set the target to be exactly the string you
specify. If you want multiple targets, you can specify them as a single
argument to --MMTT, or use multiple --MMTT options.
For example, --MMTT ''$$((oobbjjppffxx))ffoooo..oo'' might give
$(objpfx)foo.o: foo.c
-
--MMQQ _t_a_r_g_e_t
Same as --MMTT, but it quotes any characters which are special to
-
Make. --MMQQ ''$$((oobbjjppffxx))ffoooo..oo'' gives
$$(objpfx)foo.o: foo.c
The default target is automatically quoted, as if it were given with
--MMQQ.
-
--MMDD
--MMDD is equivalent to --MM --MMFF _f_i_l_e, except that
-
--EE is not implied. The driver determines _f_i_l_e based on
whether an --oo option is given. If it is, the driver uses its
argument but with a suffix of _._d, otherwise it take the
basename of the input file and applies a _._d suffix.
If --MMDD is used in conjunction with --EE, any
--oo switch is understood to specify the dependency output file
(but @pxref{dashMF,,-MF}), but if used without --EE, each --oo
is understood to specify a target object file.
Since --EE is not implied, --MMDD can be used to generate
a dependency output file as a side-effect of the compilation process.
-
--MMMMDD
Like --MMDD except mention only user header files, not system
-
header files.
-
--ffppcchh--ddeeppss
When using precompiled headers, this flag
-
will cause the dependency-output flags to also list the files from the
precompiled header's dependencies. If not specified only the
precompiled header would be listed and not the files that were used to
create it because those files are not consulted when a precompiled
header is used.
-
--ffppcchh--pprreepprroocceessss
This option allows use of a precompiled header together with --EE. It inserts a special "#pragma",
-
"#pragma GCC pch_preprocess """ in the output to mark
the place where the precompiled header was found, and its filename. When
--ffpprreepprroocceesssseedd is in use, GCC recognizes this "#pragma" and
loads the PCH.
This option is off by default, because the resulting preprocessed output
is only really suitable as input to GCC. It is switched on by
--ssaavvee--tteemmppss.
You should not write this "#pragma" in your own code, but it is
safe to edit the filename if the PCH file is available in a different
location. The filename may be absolute or it may be relative to GCC's
current directory.
-
--xx cc
-
-
--xx cc++++
-
-
--xx oobbjjeeccttiivvee--cc
-
-
--xx aasssseemmbblleerr--wwiitthh--ccpppp
Specify the source language: C, C++, Objective-C, or assembly. This has
-
nothing to do with standards conformance or extensions; it merely
selects which base syntax to expect. If you give none of these options,
cpp will deduce the language from the extension of the source file:
..cc, ..cccc, ..mm, or ..SS. Some other common
extensions for C++ and assembly are also recognized. If cpp does not
recognize the extension, it will treat the file as C; this is the most
generic mode.
_N_o_t_e_: Previous versions of cpp accepted a --llaanngg option
which selected both the language and the standards conformance level.
This option has been removed, because it conflicts with the --ll
option.
-
--ssttdd==_s_t_a_n_d_a_r_d
-
-
--aannssii
Specify the standard to which the code should conform. Currently CPP
-
knows about C and C++ standards; others may be added in the future.
_s_t_a_n_d_a_r_d
may be one of:
-
"iso9899:1990"
-
-
"c89"
The ISO C standard from 1990. cc8899 is the customary shorthand for
-
this version of the standard.
The --aannssii option is equivalent to --ssttdd==cc8899.
-
"iso9899:199409"
The 1990 C standard, as amended in 1994.
-
-
"iso9899:1999"
-
-
"c99"
-
-
"iso9899:199x"
-
-
"c9x"
The revised ISO C standard, published in December 1999. Before
-
publication, this was known as C9X.
-
"gnu89"
The 1990 C standard plus GNU extensions. This is the default.
-
-
"gnu99"
-
-
"gnu9x"
The 1999 C standard plus GNU extensions.
-
-
"c++98"
The 1998 ISO C++ standard plus amendments.
-
-
"gnu++98"
The same as --ssttdd==cc++++9988 plus GNU extensions. This is the
-
default for C++ code.
-
--II--
Split the include path. Any directories specified with --II
-
options before --II-- are searched only for headers requested with
"#include "file""; they are not searched for
"#include ". If additional directories are
specified with --II options after the --II--, those
directories are searched for all ##iinncclluuddee directives.
In addition, --II-- inhibits the use of the directory of the current
file directory as the first search directory for "#include "file"".
This option has been deprecated.
-
--nnoossttddiinncc
Do not search the standard system directories for header files.
-
Only the directories you have specified with --II options
(and the directory of the current file, if appropriate) are searched.
-
--nnoossttddiinncc++++
Do not search for header files in the C++-specific standard directories,
-
but do still search the other standard directories. (This option is
used when building the C++ library.)
-
--iinncclluuddee _f_i_l_e
Process _f_i_l_e as if "#include "file"" appeared as the first
-
line of the primary source file. However, the first directory searched
for _f_i_l_e is the preprocessor's working directory _i_n_s_t_e_a_d _o_f
the directory containing the main source file. If not found there, it
is searched for in the remainder of the "#include "..."" search
chain as normal.
If multiple --iinncclluuddee options are given, the files are included
in the order they appear on the command line.
-
--iimmaaccrrooss _f_i_l_e
Exactly like --iinncclluuddee, except that any output produced by
-
scanning _f_i_l_e is thrown away. Macros it defines remain defined.
This allows you to acquire all the macros from a header without also
processing its declarations.
All files specified by --iimmaaccrrooss are processed before all files
specified by --iinncclluuddee.
-
--iiddiirraafftteerr _d_i_r
Search _d_i_r for header files, but do it _a_f_t_e_r all
-
directories specified with --II and the standard system directories
have been exhausted. _d_i_r is treated as a system include directory.
-
--iipprreeffiixx _p_r_e_f_i_x
Specify _p_r_e_f_i_x as the prefix for subsequent --iiwwiitthhpprreeffiixx
-
options. If the prefix represents a directory, you should include the
final //.
-
--iiwwiitthhpprreeffiixx _d_i_r
-
-
--iiwwiitthhpprreeffiixxbbeeffoorree _d_i_r
Append _d_i_r to the prefix specified previously with
-
--iipprreeffiixx, and add the resulting directory to the include search
path. --iiwwiitthhpprreeffiixxbbeeffoorree puts it in the same place --II
would; --iiwwiitthhpprreeffiixx puts it where --iiddiirraafftteerr would.
-
--iissyyssrroooott _d_i_r
This option is like the ----ssyyssrroooott option, but applies only to
-
header files. See the ----ssyyssrroooott option for more information.
-
--iissyysstteemm _d_i_r
Search _d_i_r for header files, after all directories specified by
-
--II but before the standard system directories. Mark it
as a system directory, so that it gets the same special treatment as
is applied to the standard system directories.
-
--iiqquuoottee _d_i_r
Search _d_i_r only for header files requested with
-
"#include "file""; they are not searched for
"#include ", before all directories specified by
--II and before the standard system directories.
-
--ffddoollllaarrss--iinn--iiddeennttiiffiieerrss
@anchor{fdollars-in-identifiers}
-
Accept $$ in identifiers.
-
--ffeexxtteennddeedd--iiddeennttiiffiieerrss
Accept universal character names in identifiers. This option is
-
experimental; in a future version of GCC, it will be enabled by
default for C99 and C++.
-
--ffpprreepprroocceesssseedd
Indicate to the preprocessor that the input file has already been
-
preprocessed. This suppresses things like macro expansion, trigraph
conversion, escaped newline splicing, and processing of most directives.
The preprocessor still recognizes and removes comments, so that you can
pass a file preprocessed with --CC to the compiler without
problems. In this mode the integrated preprocessor is little more than
a tokenizer for the front ends.
--ffpprreepprroocceesssseedd is implicit if the input file has one of the
extensions ..ii, ..iiii or ..mmii. These are the
extensions that GCC uses for preprocessed files created by
--ssaavvee--tteemmppss.
-
--ffttaabbssttoopp==_w_i_d_t_h
Set the distance between tab stops. This helps the preprocessor report
-
correct column numbers in warnings or errors, even if tabs appear on the
line. If the value is less than 1 or greater than 100, the option is
ignored. The default is 8.
-
--ffeexxeecc--cchhaarrsseett==_c_h_a_r_s_e_t
Set the execution character set, used for string and character
-
constants. The default is UTF-8. _c_h_a_r_s_e_t can be any encoding
supported by the system's "iconv" library routine.
-
--ffwwiiddee--eexxeecc--cchhaarrsseett==_c_h_a_r_s_e_t
Set the wide execution character set, used for wide string and
-
character constants. The default is UTF-32 or UTF-16, whichever
corresponds to the width of "wchar_t". As with
--ffeexxeecc--cchhaarrsseett, _c_h_a_r_s_e_t can be any encoding supported
by the system's "iconv" library routine; however, you will have
problems with encodings that do not fit exactly in "wchar_t".
-
--ffiinnppuutt--cchhaarrsseett==_c_h_a_r_s_e_t
Set the input character set, used for translation from the character
-
set of the input file to the source character set used by GCC. If the
locale does not specify, or GCC cannot get this information from the
locale, the default is UTF-8. This can be overridden by either the locale
or this command line option. Currently the command line option takes
precedence if there's a conflict. _c_h_a_r_s_e_t can be any encoding
supported by the system's "iconv" library routine.
-
--ffwwoorrkkiinngg--ddiirreeccttoorryy
Enable generation of linemarkers in the preprocessor output that will
-
let the compiler know the current working directory at the time of
preprocessing. When this option is enabled, the preprocessor will
emit, after the initial linemarker, a second linemarker with the
current working directory followed by two slashes. GCC will use this
directory, when it's present in the preprocessed input, as the
directory emitted as the current working directory in some debugging
information formats. This option is implicitly enabled if debugging
information is enabled, but this can be inhibited with the negated
form --ffnnoo--wwoorrkkiinngg--ddiirreeccttoorryy. If the --PP flag is
present in the command line, this option has no effect, since no
"#line" directives are emitted whatsoever.
-
--ffnnoo--sshhooww--ccoolluummnn
Do not print column numbers in diagnostics. This may be necessary if
-
diagnostics are being scanned by a program that does not understand the
column numbers, such as ddeejjaaggnnuu.
-
--AA _p_r_e_d_i_c_a_t_e==_a_n_s_w_e_r
Make an assertion with the predicate _p_r_e_d_i_c_a_t_e and answer
-
_a_n_s_w_e_r. This form is preferred to the older form --AA
_p_r_e_d_i_c_a_t_e((_a_n_s_w_e_r)), which is still supported, because
it does not use shell special characters.
-
--AA --_p_r_e_d_i_c_a_t_e==_a_n_s_w_e_r
Cancel an assertion with the predicate _p_r_e_d_i_c_a_t_e and answer
-
_a_n_s_w_e_r.
-
--ddCCHHAARRSS
_C_H_A_R_S is a sequence of one or more of the following characters,
-
and must not be preceded by a space. Other characters are interpreted
by the compiler proper, or reserved for future versions of GCC, and so
are silently ignored. If you specify characters whose behavior
conflicts, the result is undefined.
-
MM
Instead of the normal output, generate a list of ##ddeeffiinnee
-
directives for all the macros defined during the execution of the
preprocessor, including predefined macros. This gives you a way of
finding out what is predefined in your version of the preprocessor.
The following command:
cpp -dM < /dev/null | sort
will show all the predefined macros and their values. Alternately to be
sure the exact same built-in preprocessor code is running you can use
this command:
gcc -dM -E - < /dev/null | sort
-
DD
Like MM except in two respects: it does _n_o_t include the
-
predefined macros, and it outputs _b_o_t_h the ##ddeeffiinnee
directives and the result of preprocessing. Both kinds of output go to
the standard output file.
-
NN
Like DD, but emit only the macro names, not their expansions.
-
-
II
Output ##iinncclluuddee directives in addition to the result of
-
preprocessing.
-
--PP
Inhibit generation of linemarkers in the output from the preprocessor.
-
This might be useful when running the preprocessor on something that is
not C code, and will be sent to a program which might be confused by the
linemarkers.
-
--CC
Do not discard comments. All comments are passed through to the output
-
file, except for comments in processed directives, which are deleted
along with the directive.
You should be prepared for side effects when using --CC; it
causes the preprocessor to treat comments as tokens in their own right.
For example, comments appearing at the start of what would be a
directive line have the effect of turning that line into an ordinary
source line, since the first token on the line is no longer a ##.
-
--CCCC
Do not discard comments, including during macro expansion. This is
-
like --CC, except that comments contained within macros are
also passed through to the output file where the macro is expanded.
In addition to the side-effects of the --CC option, the
--CCCC option causes all C++-style comments inside a macro
to be converted to C-style comments. This is to prevent later use
of that macro from inadvertently commenting out the remainder of
the source line.
The --CCCC option is generally used to support lint comments.
-
--ttrraaddiittiioonnaall--ccpppp
Try to imitate the behavior of old-fashioned C preprocessors, as
-
opposed to ISO C preprocessors.
-
--ttrriiggrraapphhss
Process trigraph sequences.
-
These are three-character sequences, all starting with ????, that
are defined by ISO C to stand for single characters. For example,
????// stands for \\, so ''????//nn'' is a character
constant for a newline. By default, GCC ignores trigraphs, but in
standard-conforming modes it converts them. See the --ssttdd and
--aannssii options.
The nine trigraphs and their replacements are
Trigraph: ??( ??) ??< ??> ??= ??/ ??' ??! ??-
Replacement: [ ] { } # \ ^ | ~
-
--rreemmaapp
Enable special code to work around file systems which only permit very
-
short file names, such as MS-DOS.
-
----hheellpp
-
-
----ttaarrggeett--hheellpp
Print text describing all the command line options instead of
-
preprocessing anything.
-
--vv
Verbose mode. Print out GNU CPP's version number at the beginning of
-
execution, and report the final form of the include path.
-
--HH
Print the name of each header file used, in addition to other normal
-
activities. Each name is indented to show how deep in the
##iinncclluuddee stack it is. Precompiled header files are also
printed, even if they are found to be invalid; an invalid precompiled
header file is printed with ......xx and a valid one with ......!! .
-
--vveerrssiioonn
-
-
----vveerrssiioonn
Print out GNU CPP's version number. With one dash, proceed to
-
preprocess as normal. With two dashes, exit immediately.
PPaassssiinngg OOppttiioonnss ttoo tthhee AAsssseemmbblleerr
You can pass options to the assembler.
-
--WWaa,,_o_p_t_i_o_n
Pass _o_p_t_i_o_n as an option to the assembler. If _o_p_t_i_o_n
-
contains commas, it is split into multiple options at the commas.
-
--XXaasssseemmbblleerr _o_p_t_i_o_n
Pass _o_p_t_i_o_n as an option to the assembler. You can use this to
-
supply system-specific assembler options which GCC does not know how to
recognize.
If you want to pass an option that takes an argument, you must use
--XXaasssseemmbblleerr twice, once for the option and once for the argument.
OOppttiioonnss ffoorr LLiinnkkiinngg
These options come into play when the compiler links object files into
an executable output file. They are meaningless if the compiler is
not doing a link step.
-
_o_b_j_e_c_t_-_f_i_l_e_-_n_a_m_e
A file name that does not end in a special recognized suffix is
-
considered to name an object file or library. (Object files are
distinguished from libraries by the linker according to the file
contents.) If linking is done, these object files are used as input
to the linker.
-
--cc
-
-
--SS
-
-
--EE
If any of these options is used, then the linker is not run, and
-
object file names should not be used as arguments.
-
--ll_l_i_b_r_a_r_y
-
-
--ll _l_i_b_r_a_r_y
Search the library named _l_i_b_r_a_r_y when linking. (The second
-
alternative with the library as a separate argument is only for
POSIX compliance and is not recommended.)
It makes a difference where in the command you write this option; the
linker searches and processes libraries and object files in the order they
are specified. Thus, ffoooo..oo --llzz bbaarr..oo searches library zz
after file _f_o_o_._o but before _b_a_r_._o. If _b_a_r_._o refers
to functions in zz, those functions may not be loaded.
The linker searches a standard list of directories for the library,
which is actually a file named _l_i_b_l_i_b_r_a_r_y_._a. The linker
then uses this file as if it had been specified precisely by name.
The directories searched include several standard system directories
plus any that you specify with --LL.
Normally the files found this way are library files---archive files
whose members are object files. The linker handles an archive file by
scanning through it for members which define symbols that have so far
been referenced but not defined. But if the file that is found is an
ordinary object file, it is linked in the usual fashion. The only
difference between using an --ll option and specifying a file name
is that --ll surrounds _l_i_b_r_a_r_y with lliibb and ..aa
and searches several directories.
-
--lloobbjjcc
You need this special case of the --ll option in order to
-
link an Objective-C or Objective-C++ program.
-
--nnoossttaarrttffiilleess
Do not use the standard system startup files when linking.
-
The standard system libraries are used normally, unless --nnoossttddlliibb
or --nnooddeeffaauullttlliibbss is used.
-
--nnooddeeffaauullttlliibbss
Do not use the standard system libraries when linking.
-
Only the libraries you specify will be passed to the linker.
The standard startup files are used normally, unless --nnoossttaarrttffiilleess
is used. The compiler may generate calls to "memcmp",
"memset", "memcpy" and "memmove".
These entries are usually resolved by entries in
libc. These entry points should be supplied through some other
mechanism when this option is specified.
-
--nnoossttddlliibb
Do not use the standard system startup files or libraries when linking.
-
No startup files and only the libraries you specify will be passed to
the linker. The compiler may generate calls to "memcmp", "memset",
"memcpy" and "memmove".
These entries are usually resolved by entries in
libc. These entry points should be supplied through some other
mechanism when this option is specified.
One of the standard libraries bypassed by --nnoossttddlliibb and
--nnooddeeffaauullttlliibbss is _l_i_b_g_c_c_._a, a library of internal subroutines
that GCC uses to overcome shortcomings of particular machines, or special
needs for some languages.
In most cases, you need _l_i_b_g_c_c_._a even when you want to avoid
other standard libraries. In other words, when you specify --nnoossttddlliibb
or --nnooddeeffaauullttlliibbss you should usually specify --llggcccc as well.
This ensures that you have no unresolved references to internal GCC
library subroutines. (For example, ____mmaaiinn, used to ensure C++
constructors will be called.)
-
--ppiiee
Produce a position independent executable on targets which support it.
-
For predictable results, you must also specify the same set of options
that were used to generate code (--ffppiiee, --ffPPIIEE,
or model suboptions) when you specify this option.
-
--rrddyynnaammiicc
Pass the flag --eexxppoorrtt--ddyynnaammiicc to the ELF linker, on targets
-
that support it. This instructs the linker to add all symbols, not
only used ones, to the dynamic symbol table. This option is needed
for some uses of "dlopen" or to allow obtaining backtraces
from within a program.
-
--ss
Remove all symbol table and relocation information from the executable.
-
-
--ssttaattiicc
On systems that support dynamic linking, this prevents linking with the shared
-
libraries. On other systems, this option has no effect.
-
--sshhaarreedd
Produce a shared object which can then be linked with other objects to
-
form an executable. Not all systems support this option. For predictable
results, you must also specify the same set of options that were used to
generate code (--ffppiicc, --ffPPIICC, or model suboptions)
when you specify this option.[1]
-
--sshhaarreedd--lliibbggcccc
-
-
--ssttaattiicc--lliibbggcccc
On systems that provide _l_i_b_g_c_c as a shared library, these options
-
force the use of either the shared or static version respectively.
If no shared version of _l_i_b_g_c_c was built when the compiler was
configured, these options have no effect.
There are several situations in which an application should use the
shared _l_i_b_g_c_c instead of the static version. The most common
of these is when the application wishes to throw and catch exceptions
across different shared libraries. In that case, each of the libraries
as well as the application itself should use the shared _l_i_b_g_c_c.
Therefore, the G++ and GCJ drivers automatically add
--sshhaarreedd--lliibbggcccc whenever you build a shared library or a main
executable, because C++ and Java programs typically use exceptions, so
this is the right thing to do.
If, instead, you use the GCC driver to create shared libraries, you may
find that they will not always be linked with the shared _l_i_b_g_c_c.
If GCC finds, at its configuration time, that you have a non-GNU linker
or a GNU linker that does not support option ----eehh--ffrraammee--hhddrr,
it will link the shared version of _l_i_b_g_c_c into shared libraries
by default. Otherwise, it will take advantage of the linker and optimize
away the linking with the shared version of _l_i_b_g_c_c, linking with
the static version of libgcc by default. This allows exceptions to
propagate through such shared libraries, without incurring relocation
costs at library load time.
However, if a library or main executable is supposed to throw or catch
exceptions, you must link it using the G++ or GCJ driver, as appropriate
for the languages used in the program, or using the option
--sshhaarreedd--lliibbggcccc, such that it is linked with the shared
_l_i_b_g_c_c.
-
--ssyymmbboolliicc
Bind references to global symbols when building a shared object. Warn
-
about any unresolved references (unless overridden by the link editor
option --XXlliinnkkeerr --zz --XXlliinnkkeerr ddeeffss). Only a few systems support
this option.
-
--XXlliinnkkeerr _o_p_t_i_o_n
Pass _o_p_t_i_o_n as an option to the linker. You can use this to
-
supply system-specific linker options which GCC does not know how to
recognize.
If you want to pass an option that takes an argument, you must use
--XXlliinnkkeerr twice, once for the option and once for the argument.
For example, to pass --aasssseerrtt ddeeffiinniittiioonnss, you must write
--XXlliinnkkeerr --aasssseerrtt --XXlliinnkkeerr ddeeffiinniittiioonnss. It does not work to write
--XXlliinnkkeerr ""--aasssseerrtt ddeeffiinniittiioonnss"", because this passes the entire
string as a single argument, which is not what the linker expects.
-
--WWll,,_o_p_t_i_o_n
Pass _o_p_t_i_o_n as an option to the linker. If _o_p_t_i_o_n contains
-
commas, it is split into multiple options at the commas.
-
--uu _s_y_m_b_o_l
Pretend the symbol _s_y_m_b_o_l is undefined, to force linking of
-
library modules to define it. You can use --uu multiple times with
different symbols to force loading of additional library modules.
OOppttiioonnss ffoorr DDiirreeccttoorryy SSeeaarrcchh
These options specify directories to search for header files, for
libraries and for parts of the compiler:
-
--II_d_i_r
Add the directory _d_i_r to the head of the list of directories to be
-
searched for header files. This can be used to override a system header
file, substituting your own version, since these directories are
searched before the system header file directories. However, you should
not use this option to add directories that contain vendor-supplied
system header files (use --iissyysstteemm for that). If you use more than
one --II option, the directories are scanned in left-to-right
order; the standard system directories come after.
If a standard system include directory, or a directory specified with
--iissyysstteemm, is also specified with --II, the --II
option will be ignored. The directory will still be searched but as a
system directory at its normal position in the system include chain.
This is to ensure that GCC's procedure to fix buggy system headers and
the ordering for the include_next directive are not inadvertently changed.
If you really need to change the search order for system directories,
use the --nnoossttddiinncc and/or --iissyysstteemm options.
-
--iiqquuoottee_d_i_r
Add the directory _d_i_r to the head of the list of directories to
-
be searched for header files only for the case of ##iinncclluuddee
""_f_i_l_e""; they are not searched for ##iinncclluuddee <<_f_i_l_e>>,
otherwise just like --II.
-
--LL_d_i_r
Add directory _d_i_r to the list of directories to be searched
-
for --ll.
-
--BB_p_r_e_f_i_x
This option specifies where to find the executables, libraries,
-
include files, and data files of the compiler itself.
The compiler driver program runs one or more of the subprograms
_c_p_p, _c_c_1, _a_s and _l_d. It tries
_p_r_e_f_i_x as a prefix for each program it tries to run, both with and
without _m_a_c_h_i_n_e//_v_e_r_s_i_o_n//.
For each subprogram to be run, the compiler driver first tries the
--BB prefix, if any. If that name is not found, or if --BB
was not specified, the driver tries two standard prefixes, which are
_/_u_s_r_/_l_i_b_/_g_c_c_/ and _/_u_s_r_/_l_o_c_a_l_/_l_i_b_/_g_c_c_/. If neither of
those results in a file name that is found, the unmodified program
name is searched for using the directories specified in your
PPAATTHH environment variable.
The compiler will check to see if the path provided by the --BB
refers to a directory, and if necessary it will add a directory
separator character at the end of the path.
--BB prefixes that effectively specify directory names also apply
to libraries in the linker, because the compiler translates these
options into --LL options for the linker. They also apply to
includes files in the preprocessor, because the compiler translates these
options into --iissyysstteemm options for the preprocessor. In this case,
the compiler appends iinncclluuddee to the prefix.
The run-time support file _l_i_b_g_c_c_._a can also be searched for using
the --BB prefix, if needed. If it is not found there, the two
standard prefixes above are tried, and that is all. The file is left
out of the link if it is not found by those means.
Another way to specify a prefix much like the --BB prefix is to use
the environment variable GGCCCC__EEXXEECC__PPRREEFFIIXX.
As a special kludge, if the path provided by --BB is
_[_d_i_r_/_]_s_t_a_g_e_N_/, where _N is a number in the range 0 to
9, then it will be replaced by _[_d_i_r_/_]_i_n_c_l_u_d_e. This is to help
with boot-strapping the compiler.
-
--ssppeeccss==_f_i_l_e
Process _f_i_l_e after the compiler reads in the standard _s_p_e_c_s
-
file, in order to override the defaults that the _g_c_c driver
program uses when determining what switches to pass to _c_c_1,
_c_c_1_p_l_u_s, _a_s, _l_d, etc. More than one
--ssppeeccss==_f_i_l_e can be specified on the command line, and they
are processed in order, from left to right.
-
----ssyyssrroooott==_d_i_r
Use _d_i_r as the logical root directory for headers and libraries.
-
For example, if the compiler would normally search for headers in
_/_u_s_r_/_i_n_c_l_u_d_e and libraries in _/_u_s_r_/_l_i_b, it will instead
search _d_i_r_/_u_s_r_/_i_n_c_l_u_d_e and _d_i_r_/_u_s_r_/_l_i_b.
If you use both this option and the --iissyyssrroooott option, then
the ----ssyyssrroooott option will apply to libraries, but the
--iissyyssrroooott option will apply to header files.
The GNU linker (beginning with version 2.16) has the necessary support
for this option. If your linker does not support this option, the
header file aspect of ----ssyyssrroooott will still work, but the
library aspect will not.
-
--II--
This option has been deprecated. Please use --iiqquuoottee instead for
-
--II directories before the --II-- and remove the --II--.
Any directories you specify with --II options before the --II--
option are searched only for the case of ##iinncclluuddee ""_f_i_l_e"";
they are not searched for ##iinncclluuddee <<_f_i_l_e>>.
If additional directories are specified with --II options after
the --II--, these directories are searched for all ##iinncclluuddee
directives. (Ordinarily _a_l_l --II directories are used
this way.)
In addition, the --II-- option inhibits the use of the current
directory (where the current input file came from) as the first search
directory for ##iinncclluuddee ""_f_i_l_e"". There is no way to
override this effect of --II--. With --II.. you can specify
searching the directory which was current when the compiler was
invoked. That is not exactly the same as what the preprocessor does
by default, but it is often satisfactory.
--II-- does not inhibit the use of the standard system directories
for header files. Thus, --II-- and --nnoossttddiinncc are
independent.
SSppeecciiffyyiinngg TTaarrggeett MMaacchhiinnee aanndd CCoommppiilleerr VVeerrssiioonn
The usual way to run GCC is to run the executable called _g_c_c, or
_<_m_a_c_h_i_n_e_>_-_g_c_c when cross-compiling, or
_<_m_a_c_h_i_n_e_>_-_g_c_c_-_<_v_e_r_s_i_o_n_> to run a version other than the one that
was installed last. Sometimes this is inconvenient, so GCC provides
options that will switch to another cross-compiler or version.
-
--bb _m_a_c_h_i_n_e
The argument _m_a_c_h_i_n_e specifies the target machine for compilation.
-
The value to use for _m_a_c_h_i_n_e is the same as was specified as the
machine type when configuring GCC as a cross-compiler. For
example, if a cross-compiler was configured with ccoonnffiigguurree
aarrmm--eellff, meaning to compile for an arm processor with elf binaries,
then you would specify --bb aarrmm--eellff to run that cross compiler.
Because there are other options beginning with --bb, the
configuration must contain a hyphen.
-
--VV _v_e_r_s_i_o_n
The argument _v_e_r_s_i_o_n specifies which version of GCC to run.
-
This is useful when multiple versions are installed. For example,
_v_e_r_s_i_o_n might be 44..00, meaning to run GCC version 4.0.
The --VV and --bb options work by running the
_<_m_a_c_h_i_n_e_>_-_g_c_c_-_<_v_e_r_s_i_o_n_> executable, so there's no real reason to
use them if you can just run that directly.
HHaarrddwwaarree MMooddeellss aanndd CCoonnffiigguurraattiioonnss
Earlier we discussed the standard option --bb which chooses among
different installed compilers for completely different target
machines, such as VAX vs. 68000 vs. 80386.
In addition, each of these target machine types can have its own
special options, starting with --mm, to choose among various
hardware models or configurations---for example, 68010 vs 68020,
floating coprocessor or none. A single installed version of the
compiler can compile for any model or configuration, according to the
options specified.
Some configurations of the compiler also support additional special
options, usually for compatibility with other compilers on the same
platform.
_A_R_C _O_p_t_i_o_n_s
These options are defined for ARC implementations:
-
--EELL
Compile code for little endian mode. This is the default.
-
-
--EEBB
Compile code for big endian mode.
-
-
--mmmmaannggllee--ccppuu
Prepend the name of the cpu to all public symbol names.
-
In multiple-processor systems, there are many ARC variants with different
instruction and register set characteristics. This flag prevents code
compiled for one cpu to be linked with code compiled for another.
No facility exists for handling variants that are "almost identical".
This is an all or nothing option.
-
--mmccppuu==_c_p_u
Compile code for ARC variant _c_p_u.
-
Which variants are supported depend on the configuration.
All variants support --mmccppuu==bbaassee, this is the default.
-
--mmtteexxtt==_t_e_x_t_-_s_e_c_t_i_o_n
-
-
--mmddaattaa==_d_a_t_a_-_s_e_c_t_i_o_n
-
-
--mmrrooddaattaa==_r_e_a_d_o_n_l_y_-_d_a_t_a_-_s_e_c_t_i_o_n
Put functions, data, and readonly data in _t_e_x_t_-_s_e_c_t_i_o_n,
-
_d_a_t_a_-_s_e_c_t_i_o_n, and _r_e_a_d_o_n_l_y_-_d_a_t_a_-_s_e_c_t_i_o_n respectively
by default. This can be overridden with the "section" attribute.
_A_R_M _O_p_t_i_o_n_s
These --mm options are defined for Advanced RISC Machines (ARM)
architectures:
-
--mmaabbii==_n_a_m_e
Generate code for the specified ABI. Permissible values are: aappccss--ggnnuu,
-
aattppccss, aaaappccss, aaaappccss--lliinnuuxx and iiwwmmmmxxtt.
-
--mmaappccss--ffrraammee
Generate a stack frame that is compliant with the ARM Procedure Call
-
Standard for all functions, even if this is not strictly necessary for
correct execution of the code. Specifying --ffoommiitt--ffrraammee--ppooiinntteerr
with this option will cause the stack frames not to be generated for
leaf functions. The default is --mmnnoo--aappccss--ffrraammee.
-
--mmaappccss
This is a synonym for --mmaappccss--ffrraammee.
-
-
--mmtthhuummbb--iinntteerrwwoorrkk
Generate code which supports calling between the ARM and Thumb
-
instruction sets. Without this option the two instruction sets cannot
be reliably used inside one program. The default is
--mmnnoo--tthhuummbb--iinntteerrwwoorrkk, since slightly larger code is generated
when --mmtthhuummbb--iinntteerrwwoorrkk is specified.
-
--mmnnoo--sscchheedd--pprroolloogg
Prevent the reordering of instructions in the function prolog, or the
-
merging of those instruction with the instructions in the function's
body. This means that all functions will start with a recognizable set
of instructions (or in fact one of a choice from a small set of
different function prologues), and this information can be used to
locate the start if functions inside an executable piece of code. The
default is --mmsscchheedd--pprroolloogg.
-
--mmhhaarrdd--ffllooaatt
Generate output containing floating point instructions. This is the
-
default.
-
--mmssoofftt--ffllooaatt
Generate output containing library calls for floating point.
-
WWaarrnniinngg:: the requisite libraries are not available for all ARM
targets. Normally the facilities of the machine's usual C compiler are
used, but this cannot be done directly in cross-compilation. You must make
your own arrangements to provide suitable library functions for
cross-compilation.
--mmssoofftt--ffllooaatt changes the calling convention in the output file;
therefore, it is only useful if you compile _a_l_l of a program with
this option. In particular, you need to compile _l_i_b_g_c_c_._a, the
library that comes with GCC, with --mmssoofftt--ffllooaatt in order for
this to work.
-
--mmffllooaatt--aabbii==_n_a_m_e
Specifies which ABI to use for floating point values. Permissible values
-
are: ssoofftt, ssooffttffpp and hhaarrdd.
ssoofftt and hhaarrdd are equivalent to --mmssoofftt--ffllooaatt
and --mmhhaarrdd--ffllooaatt respectively. ssooffttffpp allows the generation
of floating point instructions, but still uses the soft-float calling
conventions.
-
--mmlliittttllee--eennddiiaann
Generate code for a processor running in little-endian mode. This is
-
the default for all standard configurations.
-
--mmbbiigg--eennddiiaann
Generate code for a processor running in big-endian mode; the default is
-
to compile code for a little-endian processor.
-
--mmwwoorrddss--lliittttllee--eennddiiaann
This option only applies when generating code for big-endian processors.
-
Generate code for a little-endian word order but a big-endian byte
order. That is, a byte order of the form 3322110077665544. Note: this
option should only be used if you require compatibility with code for
big-endian ARM processors generated by versions of the compiler prior to
2.8.
-
--mmccppuu==_n_a_m_e
This specifies the name of the target ARM processor. GCC uses this name
-
to determine what kind of instructions it can emit when generating
assembly code. Permissible names are: aarrmm22, aarrmm225500,
aarrmm33, aarrmm66, aarrmm6600, aarrmm660000, aarrmm661100,
aarrmm662200, aarrmm77, aarrmm77mm, aarrmm77dd, aarrmm77ddmm,
aarrmm77ddii, aarrmm77ddmmii, aarrmm7700, aarrmm770000,
aarrmm770000ii, aarrmm771100, aarrmm771100cc, aarrmm77110000,
aarrmm77550000, aarrmm77550000ffee, aarrmm77ttddmmii, aarrmm77ttddmmii--ss,
aarrmm88, ssttrroonnggaarrmm, ssttrroonnggaarrmm111100, ssttrroonnggaarrmm11110000,
aarrmm88, aarrmm881100, aarrmm99, aarrmm99ee, aarrmm992200,
aarrmm992200tt, aarrmm992222tt, aarrmm994466ee--ss, aarrmm996666ee--ss,
aarrmm996688ee--ss, aarrmm992266eejj--ss, aarrmm994400tt, aarrmm99ttddmmii,
aarrmm1100ttddmmii, aarrmm11002200tt, aarrmm11002266eejj--ss,
aarrmm1100ee, aarrmm11002200ee, aarrmm11002222ee,
aarrmm11113366jj--ss, aarrmm11113366jjff--ss, mmppccoorree, mmppccoorreennoovvffpp,
aarrmm11117766jjzz--ss, aarrmm11117766jjzzff--ss, xxssccaallee, iiwwmmmmxxtt,
eepp99331122.
-
--mmttuunnee==_n_a_m_e
This option is very similar to the --mmccppuu== option, except that
-
instead of specifying the actual target processor type, and hence
restricting which instructions can be used, it specifies that GCC should
tune the performance of the code as if the target were of the type
specified in this option, but still choosing the instructions that it
will generate based on the cpu specified by a --mmccppuu== option.
For some ARM implementations better performance can be obtained by using
this option.
-
--mmaarrcchh==_n_a_m_e
This specifies the name of the target ARM architecture. GCC uses this
-
name to determine what kind of instructions it can emit when generating
assembly code. This option can be used in conjunction with or instead
of the --mmccppuu== option. Permissible names are: aarrmmvv22,
aarrmmvv22aa, aarrmmvv33, aarrmmvv33mm, aarrmmvv44, aarrmmvv44tt,
aarrmmvv55, aarrmmvv55tt, aarrmmvv55ttee, aarrmmvv66, aarrmmvv66jj,
iiwwmmmmxxtt, eepp99331122.
-
--mmffppuu==_n_a_m_e
-
-
--mmffppee==_n_u_m_b_e_r
-
-
--mmffpp==_n_u_m_b_e_r
This specifies what floating point hardware (or hardware emulation) is
-
available on the target. Permissible names are: ffppaa, ffppee22,
ffppee33, mmaavveerriicckk, vvffpp. --mmffpp and --mmffppee
are synonyms for --mmffppuu=ffppee_n_u_m_b_e_r, for compatibility
with older versions of GCC.
If --mmssoofftt--ffllooaatt is specified this specifies the format of
floating point values.
-
--mmssttrruuccttuurree--ssiizzee--bboouunnddaarryy==_n
The size of all structures and unions will be rounded up to a multiple
-
of the number of bits set by this option. Permissible values are 8, 32
and 64. The default value varies for different toolchains. For the COFF
targeted toolchain the default value is 8. A value of 64 is only allowed
if the underlying ABI supports it.
Specifying the larger number can produce faster, more efficient code, but
can also increase the size of the program. Different values are potentially
incompatible. Code compiled with one value cannot necessarily expect to
work with code or libraries compiled with another value, if they exchange
information using structures or unions.
-
--mmaabboorrtt--oonn--nnoorreettuurrnn
Generate a call to the function "abort" at the end of a
-
"noreturn" function. It will be executed if the function tries to
return.
-
--mmlloonngg--ccaallllss
-
-
--mmnnoo--lloonngg--ccaallllss
Tells the compiler to perform function calls by first loading the
-
address of the function into a register and then performing a subroutine
call on this register. This switch is needed if the target function
will lie outside of the 64 megabyte addressing range of the offset based
version of subroutine call instruction.
Even if this switch is enabled, not all function calls will be turned
into long calls. The heuristic is that static functions, functions
which have the sshhoorrtt--ccaallll attribute, functions that are inside
the scope of a ##pprraaggmmaa nnoo__lloonngg__ccaallllss directive and functions whose
definitions have already been compiled within the current compilation
unit, will not be turned into long calls. The exception to this rule is
that weak function definitions, functions with the lloonngg--ccaallll
attribute or the sseeccttiioonn attribute, and functions that are within
the scope of a ##pprraaggmmaa lloonngg__ccaallllss directive, will always be
turned into long calls.
This feature is not enabled by default. Specifying
--mmnnoo--lloonngg--ccaallllss will restore the default behavior, as will
placing the function calls within the scope of a ##pprraaggmmaa
lloonngg__ccaallllss__ooffff directive. Note these switches have no effect on how
the compiler generates code to handle function calls via function
pointers.
-
--mmnnoopp--ffuunn--ddlllliimmppoorrtt
Disable support for the "dllimport" attribute.
-
-
--mmssiinnggllee--ppiicc--bbaassee
Treat the register used for PIC addressing as read-only, rather than
-
loading it in the prologue for each function. The run-time system is
responsible for initializing this register with an appropriate value
before execution begins.
-
--mmppiicc--rreeggiisstteerr==_r_e_g
Specify the register to be used for PIC addressing. The default is R10
-
unless stack-checking is enabled, when R9 is used.
-
--mmcciirrrruuss--ffiixx--iinnvvaalliidd--iinnssnnss
Insert NOPs into the instruction stream to in order to work around
-
problems with invalid Maverick instruction combinations. This option
is only valid if the --mmccppuu==eepp99331122 option has been used to
enable generation of instructions for the Cirrus Maverick floating
point co-processor. This option is not enabled by default, since the
problem is only present in older Maverick implementations. The default
can be re-enabled by use of the --mmnnoo--cciirrrruuss--ffiixx--iinnvvaalliidd--iinnssnnss
switch.
-
--mmppookkee--ffuunnccttiioonn--nnaammee
Write the name of each function into the text section, directly
-
preceding the function prologue. The generated code is similar to this:
t0
.ascii "arm_poke_function_name", 0
.align
t1
.word 0xff000000 + (t1 - t0)
arm_poke_function_name
mov ip, sp
stmfd sp!, {fp, ip, lr, pc}
sub fp, ip, #4
When performing a stack backtrace, code can inspect the value of
"pc" stored at "fp + 0". If the trace function then looks at
location "pc - 12" and the top 8 bits are set, then we know that
there is a function name embedded immediately preceding this location
and has length "((pc[-3]) & 0xff000000)".
-
--mmtthhuummbb
Generate code for the 16-bit Thumb instruction set. The default is to
-
use the 32-bit ARM instruction set.
-
--mmttppccss--ffrraammee
Generate a stack frame that is compliant with the Thumb Procedure Call
-
Standard for all non-leaf functions. (A leaf function is one that does
not call any other functions.) The default is --mmnnoo--ttppccss--ffrraammee.
-
--mmttppccss--lleeaaff--ffrraammee
Generate a stack frame that is compliant with the Thumb Procedure Call
-
Standard for all leaf functions. (A leaf function is one that does
not call any other functions.) The default is --mmnnoo--aappccss--lleeaaff--ffrraammee.
-
--mmccaalllleeee--ssuuppeerr--iinntteerrwwoorrkkiinngg
Gives all externally visible functions in the file being compiled an ARM
-
instruction set header which switches to Thumb mode before executing the
rest of the function. This allows these functions to be called from
non-interworking code.
-
--mmccaalllleerr--ssuuppeerr--iinntteerrwwoorrkkiinngg
Allows calls via function pointers (including virtual functions) to
-
execute correctly regardless of whether the target code has been
compiled for interworking or not. There is a small overhead in the cost
of executing a function pointer if this option is enabled.
-
--mmttpp==_n_a_m_e
Specify the access model for the thread local storage pointer. The valid
-
models are ssoofftt, which generates calls to "__aeabi_read_tp",
ccpp1155, which fetches the thread pointer from "cp15" directly
(supported in the arm6k architecture), and aauuttoo, which uses the
best available method for the selected processor. The default setting is
aauuttoo.
_A_V_R _O_p_t_i_o_n_s
These options are defined for AVR implementations:
-
--mmmmccuu==_m_c_u
Specify ATMEL AVR instruction set or MCU type.
-
Instruction set avr1 is for the minimal AVR core, not supported by the C
compiler, only for assembler programs (MCU types: at90s1200, attiny10,
attiny11, attiny12, attiny15, attiny28).
Instruction set avr2 (default) is for the classic AVR core with up to
8K program memory space (MCU types: at90s2313, at90s2323, attiny22,
at90s2333, at90s2343, at90s4414, at90s4433, at90s4434, at90s8515,
at90c8534, at90s8535).
Instruction set avr3 is for the classic AVR core with up to 128K program
memory space (MCU types: atmega103, atmega603, at43usb320, at76c711).
Instruction set avr4 is for the enhanced AVR core with up to 8K program
memory space (MCU types: atmega8, atmega83, atmega85).
Instruction set avr5 is for the enhanced AVR core with up to 128K program
memory space (MCU types: atmega16, atmega161, atmega163, atmega32, atmega323,
atmega64, atmega128, at43usb355, at94k).
-
--mmssiizzee
Output instruction sizes to the asm file.
-
-
--mmiinniitt--ssttaacckk==_N
Specify the initial stack address, which may be a symbol or numeric value,
-
____ssttaacckk is the default.
-
--mmnnoo--iinntteerrrruuppttss
Generated code is not compatible with hardware interrupts.
-
Code size will be smaller.
-
--mmccaallll--pprroolloogguueess
Functions prologues/epilogues expanded as call to appropriate
-
subroutines. Code size will be smaller.
-
--mmnnoo--ttaabblleejjuummpp
Do not generate tablejump insns which sometimes increase code size.
-
-
--mmttiinnyy--ssttaacckk
Change only the low 8 bits of the stack pointer.
-
-
--mmiinntt88
Assume int to be 8 bit integer. This affects the sizes of all types: A
-
char will be 1 byte, an int will be 1 byte, an long will be 2 bytes
and long long will be 4 bytes. Please note that this option does not
comply to the C standards, but it will provide you with smaller code
size.
_B_l_a_c_k_f_i_n _O_p_t_i_o_n_s
-
--mmoommiitt--lleeaaff--ffrraammee--ppooiinntteerr
Don't keep the frame pointer in a register for leaf functions. This
-
avoids the instructions to save, set up and restore frame pointers and
makes an extra register available in leaf functions. The option
--ffoommiitt--ffrraammee--ppooiinntteerr removes the frame pointer for all functions
which might make debugging harder.
-
--mmssppeecclldd--aannoommaallyy
When enabled, the compiler will ensure that the generated code does not
-
contain speculative loads after jump instructions. This option is enabled
by default.
-
--mmnnoo--ssppeecclldd--aannoommaallyy
Don't generate extra code to prevent speculative loads from occurring.
-
-
--mmccssyynncc--aannoommaallyy
When enabled, the compiler will ensure that the generated code does not
-
contain CSYNC or SSYNC instructions too soon after conditional branches.
This option is enabled by default.
-
--mmnnoo--ccssyynncc--aannoommaallyy
Don't generate extra code to prevent CSYNC or SSYNC instructions from
-
occurring too soon after a conditional branch.
-
--mmllooww--6644kk
When enabled, the compiler is free to take advantage of the knowledge that
-
the entire program fits into the low 64k of memory.
-
--mmnnoo--llooww--6644kk
Assume that the program is arbitrarily large. This is the default.
-
-
--mmiidd--sshhaarreedd--lliibbrraarryy
Generate code that supports shared libraries via the library ID method.
-
This allows for execute in place and shared libraries in an environment
without virtual memory management. This option implies --ffPPIICC.
-
--mmnnoo--iidd--sshhaarreedd--lliibbrraarryy
Generate code that doesn't assume ID based shared libraries are being used.
-
This is the default.
-
--mmsshhaarreedd--lliibbrraarryy--iidd==nn
Specified the identification number of the ID based shared library being
-
compiled. Specifying a value of 0 will generate more compact code, specifying
other values will force the allocation of that number to the current
library but is no more space or time efficient than omitting this option.
-
--mmlloonngg--ccaallllss
-
-
--mmnnoo--lloonngg--ccaallllss
Tells the compiler to perform function calls by first loading the
-
address of the function into a register and then performing a subroutine
call on this register. This switch is needed if the target function
will lie outside of the 24 bit addressing range of the offset based
version of subroutine call instruction.
This feature is not enabled by default. Specifying
--mmnnoo--lloonngg--ccaallllss will restore the default behavior. Note these
switches have no effect on how the compiler generates code to handle
function calls via function pointers.
_C_R_I_S _O_p_t_i_o_n_s
These options are defined specifically for the CRIS ports.
-
--mmaarrcchh==_a_r_c_h_i_t_e_c_t_u_r_e_-_t_y_p_e
-
-
--mmccppuu==_a_r_c_h_i_t_e_c_t_u_r_e_-_t_y_p_e
Generate code for the specified architecture. The choices for
-
_a_r_c_h_i_t_e_c_t_u_r_e_-_t_y_p_e are vv33, vv88 and vv1100 for
respectively ETRAX 4, ETRAX 100, and ETRAX 100 LX.
Default is vv00 except for cris-axis-linux-gnu, where the default is
vv1100.
-
--mmttuunnee==_a_r_c_h_i_t_e_c_t_u_r_e_-_t_y_p_e
Tune to _a_r_c_h_i_t_e_c_t_u_r_e_-_t_y_p_e everything applicable about the generated
-
code, except for the ABI and the set of available instructions. The
choices for _a_r_c_h_i_t_e_c_t_u_r_e_-_t_y_p_e are the same as for
--mmaarrcchh==_a_r_c_h_i_t_e_c_t_u_r_e_-_t_y_p_e.
-
--mmmmaaxx--ssttaacckk--ffrraammee==_n
Warn when the stack frame of a function exceeds _n bytes.
-
-
--mmeelliinnuuxx--ssttaacckkssiizzee==_n
Only available with the ccrriiss--aaxxiiss--aaoouutt target. Arranges for
-
indications in the program to the kernel loader that the stack of the
program should be set to _n bytes.
-
--mmeettrraaxx44
-
-
--mmeettrraaxx110000
The options --mmeettrraaxx44 and --mmeettrraaxx110000 are synonyms for
-
--mmaarrcchh==vv33 and --mmaarrcchh==vv88 respectively.
-
--mmmmuull--bbuugg--wwoorrkkaarroouunndd
-
-
--mmnnoo--mmuull--bbuugg--wwoorrkkaarroouunndd
Work around a bug in the "muls" and "mulu" instructions for CPU
-
models where it applies. This option is active by default.
-
--mmppddeebbuugg
Enable CRIS-specific verbose debug-related information in the assembly
-
code. This option also has the effect to turn off the ##NNOO__AAPPPP
formatted-code indicator to the assembler at the beginning of the
assembly file.
-
--mmcccc--iinniitt
Do not use condition-code results from previous instruction; always emit
-
compare and test instructions before use of condition codes.
-
--mmnnoo--ssiiddee--eeffffeeccttss
Do not emit instructions with side-effects in addressing modes other than
-
post-increment.
-
--mmssttaacckk--aalliiggnn
-
-
--mmnnoo--ssttaacckk--aalliiggnn
-
-
--mmddaattaa--aalliiggnn
-
-
--mmnnoo--ddaattaa--aalliiggnn
-
-
--mmccoonnsstt--aalliiggnn
-
-
--mmnnoo--ccoonnsstt--aalliiggnn
These options (no-options) arranges (eliminate arrangements) for the
-
stack-frame, individual data and constants to be aligned for the maximum
single data access size for the chosen CPU model. The default is to
arrange for 32-bit alignment. ABI details such as structure layout are
not affected by these options.
-
--mm3322--bbiitt
-
-
--mm1166--bbiitt
-
-
--mm88--bbiitt
Similar to the stack- data- and const-align options above, these options
-
arrange for stack-frame, writable data and constants to all be 32-bit,
16-bit or 8-bit aligned. The default is 32-bit alignment.
-
--mmnnoo--pprroolloogguuee--eeppiilloogguuee
-
-
--mmpprroolloogguuee--eeppiilloogguuee
With --mmnnoo--pprroolloogguuee--eeppiilloogguuee, the normal function prologue and
-
epilogue that sets up the stack-frame are omitted and no return
instructions or return sequences are generated in the code. Use this
option only together with visual inspection of the compiled code: no
warnings or errors are generated when call-saved registers must be saved,
or storage for local variable needs to be allocated.
-
--mmnnoo--ggoottpplltt
-
-
--mmggoottpplltt
With --ffppiicc and --ffPPIICC, don't generate (do generate)
-
instruction sequences that load addresses for functions from the PLT part
of the GOT rather than (traditional on other architectures) calls to the
PLT. The default is --mmggoottpplltt.
-
--mmaaoouutt
Legacy no-op option only recognized with the cris-axis-aout target.
-
-
--mmeellff
Legacy no-op option only recognized with the cris-axis-elf and
-
cris-axis-linux-gnu targets.
-
--mmeelliinnuuxx
Only recognized with the cris-axis-aout target, where it selects a
-
GNU/linux-like multilib, include files and instruction set for
--mmaarrcchh==vv88.
-
--mmlliinnuuxx
Legacy no-op option only recognized with the cris-axis-linux-gnu target.
-
-
--ssiimm
This option, recognized for the cris-axis-aout and cris-axis-elf arranges
-
to link with input-output functions from a simulator library. Code,
initialized data and zero-initialized data are allocated consecutively.
-
--ssiimm22
Like --ssiimm, but pass linker options to locate initialized data at
-
0x40000000 and zero-initialized data at 0x80000000.
_C_R_X _O_p_t_i_o_n_s
These options are defined specifically for the CRX ports.
-
--mmmmaacc
Enable the use of multiply-accumulate instructions. Disabled by default.
-
-
--mmppuusshh--aarrggss
Push instructions will be used to pass outgoing arguments when functions
-
are called. Enabled by default.
_D_a_r_w_i_n _O_p_t_i_o_n_s
These options are defined for all architectures running the Darwin operating
system.
FSF GCC on Darwin does not create "fat" object files; it will create
an object file for the single architecture that it was built to
target. Apple's GCC on Darwin does create "fat" files if multiple
--aarrcchh options are used; it does so by running the compiler or
linker multiple times and joining the results together with
_l_i_p_o.
The subtype of the file created (like ppppcc77440000 or ppppcc997700 or
ii668866) is determined by the flags that specify the ISA
that GCC is targetting, like --mmccppuu or --mmaarrcchh. The
--ffoorrccee__ccppuussuubbttyyppee__AALLLL option can be used to override this.
The Darwin tools vary in their behavior when presented with an ISA
mismatch. The assembler, _a_s, will only permit instructions to
be used that are valid for the subtype of the file it is generating,
so you cannot put 64-bit instructions in an ppppcc775500 object file.
The linker for shared libraries, _/_u_s_r_/_b_i_n_/_l_i_b_t_o_o_l, will fail
and print an error if asked to create a shared library with a less
restrictive subtype than its input files (for instance, trying to put
a ppppcc997700 object file in a ppppcc77440000 library). The linker
for executables, _l_d, will quietly give the executable the most
restrictive subtype of any of its input files.
-
--FF_d_i_r
Add the framework directory _d_i_r to the head of the list of
-
directories to be searched for header files. These directories are
interleaved with those specified by --II options and are
scanned in a left-to-right order.
A framework directory is a directory with frameworks in it. A
framework is a directory with a ""HHeeaaddeerrss"" and/or
""PPrriivvaatteeHHeeaaddeerrss"" directory contained directly in it that ends
in ""..ffrraammeewwoorrkk"". The name of a framework is the name of this
directory excluding the ""..ffrraammeewwoorrkk"". Headers associated with
the framework are found in one of those two directories, with
""HHeeaaddeerrss"" being searched first. A subframework is a framework
directory that is in a framework's ""FFrraammeewwoorrkkss"" directory.
Includes of subframework headers can only appear in a header of a
framework that contains the subframework, or in a sibling subframework
header. Two subframeworks are siblings if they occur in the same
framework. A subframework should not have the same name as a
framework, a warning will be issued if this is violated. Currently a
subframework cannot have subframeworks, in the future, the mechanism
may be extended to support this. The standard frameworks can be found
in ""//SSyysstteemm//LLiibbrraarryy//FFrraammeewwoorrkkss"" and
""//LLiibbrraarryy//FFrraammeewwoorrkkss"". An example include looks like
"#include ", where FFrraammeewwoorrkk denotes
the name of the framework and header.h is found in the
""PPrriivvaatteeHHeeaaddeerrss"" or ""HHeeaaddeerrss"" directory.
-
--gguusseedd
Emit debugging information for symbols that are used. For STABS
-
debugging format, this enables --ffeelliimmiinnaattee--uunnuusseedd--ddeebbuugg--ssyymmbboollss.
This is by default ON.
-
--ggffuullll
Emit debugging information for all symbols and types.
-
-
--mmmmaaccoossxx--vveerrssiioonn--mmiinn==_v_e_r_s_i_o_n
The earliest version of MacOS X that this executable will run on
-
is _v_e_r_s_i_o_n. Typical values of _v_e_r_s_i_o_n include 10.1,
10.2, and 10.3.9.
The default for this option is to make choices that seem to be most
useful.
-
--mmoonnee--bbyyttee--bbooooll
Override the defaults for bbooooll so that ssiizzeeooff((bbooooll))====11.
-
By default ssiizzeeooff((bbooooll)) is 44 when compiling for
Darwin/PowerPC and 11 when compiling for Darwin/x86, so this
option has no effect on x86.
WWaarrnniinngg:: The --mmoonnee--bbyyttee--bbooooll switch causes GCC
to generate code that is not binary compatible with code generated
without that switch. Using this switch may require recompiling all
other modules in a program, including system libraries. Use this
switch to conform to a non-default data model.
-
--mmffiixx--aanndd--ccoonnttiinnuuee
-
-
--ffffiixx--aanndd--ccoonnttiinnuuee
-
-
--ffiinnddiirreecctt--ddaattaa
Generate code suitable for fast turn around development. Needed to
-
enable gdb to dynamically load ".o" files into already running
programs. --ffiinnddiirreecctt--ddaattaa and --ffffiixx--aanndd--ccoonnttiinnuuee
are provided for backwards compatibility.
-
--aallll__llooaadd
Loads all members of static archive libraries.
-
See man _l_d(1) for more information.
-
--aarrcchh__eerrrroorrss__ffaattaall
Cause the errors having to do with files that have the wrong architecture
-
to be fatal.
-
--bbiinndd__aatt__llooaadd
Causes the output file to be marked such that the dynamic linker will
-
bind all undefined references when the file is loaded or launched.
-
--bbuunnddllee
Produce a Mach-o bundle format file.
-
See man _l_d(1) for more information.
-
--bbuunnddllee__llooaaddeerr _e_x_e_c_u_t_a_b_l_e
This option specifies the _e_x_e_c_u_t_a_b_l_e that will be loading the build
-
output file being linked. See man _l_d(1) for more information.
-
--ddyynnaammiicclliibb
When passed this option, GCC will produce a dynamic library instead of
-
an executable when linking, using the Darwin _l_i_b_t_o_o_l command.
-
--ffoorrccee__ccppuussuubbttyyppee__AALLLL
This causes GCC's output file to have the _A_L_L subtype, instead of
-
one controlled by the --mmccppuu or --mmaarrcchh option.
-
--aalllloowwaabbllee__cclliieenntt _c_l_i_e_n_t___n_a_m_e
-
-
--cclliieenntt__nnaammee
-
-
--ccoommppaattiibbiilliittyy__vveerrssiioonn
-
-
--ccuurrrreenntt__vveerrssiioonn
-
-
--ddeeaadd__ssttrriipp
-
-
--ddeeppeennddeennccyy--ffiillee
-
-
--ddyylliibb__ffiillee
-
-
--ddyylliinnkkeerr__iinnssttaallll__nnaammee
-
-
--ddyynnaammiicc
-
-
--eexxppoorrtteedd__ssyymmbboollss__lliisstt
-
-
--ffiilleelliisstt
-
-
--ffllaatt__nnaammeessppaaccee
-
-
--ffoorrccee__ffllaatt__nnaammeessppaaccee
-
-
--hheeaaddeerrppaadd__mmaaxx__iinnssttaallll__nnaammeess
-
-
--iimmaaggee__bbaassee
-
-
--iinniitt
-
-
--iinnssttaallll__nnaammee
-
-
--kkeeeepp__pprriivvaattee__eexxtteerrnnss
-
-
--mmuullttii__mmoodduullee
-
-
--mmuullttiippllyy__ddeeffiinneedd
-
-
--mmuullttiippllyy__ddeeffiinneedd__uunnuusseedd
-
-
--nnooaallll__llooaadd
-
-
--nnoo__ddeeaadd__ssttrriipp__iinniittss__aanndd__tteerrmmss
-
-
--nnooffiixxpprreebbiinnddiinngg
-
-
--nnoommuullttiiddeeffss
-
-
--nnoopprreebbiinndd
-
-
--nnoosseegglliinnkkeeddiitt
-
-
--ppaaggeezzeerroo__ssiizzee
-
-
--pprreebbiinndd
-
-
--pprreebbiinndd__aallll__ttwwoolleevveell__mmoodduulleess
-
-
--pprriivvaattee__bbuunnddllee
-
-
--rreeaadd__oonnllyy__rreellooccss
-
-
--sseeccttaalliiggnn
-
-
--sseeccttoobbjjeeccttssyymmbboollss
-
-
--wwhhyyllooaadd
-
-
--sseegg11aaddddrr
-
-
--sseeccttccrreeaattee
-
-
--sseeccttoobbjjeeccttssyymmbboollss
-
-
--sseeccttoorrddeerr
-
-
--sseeggaaddddrr
-
-
--sseeggss__rreeaadd__oonnllyy__aaddddrr
-
-
--sseeggss__rreeaadd__wwrriittee__aaddddrr
-
-
--sseegg__aaddddrr__ttaabbllee
-
-
--sseegg__aaddddrr__ttaabbllee__ffiilleennaammee
-
-
--sseegglliinnkkeeddiitt
-
-
--sseeggpprroott
-
-
--sseeggss__rreeaadd__oonnllyy__aaddddrr
-
-
--sseeggss__rreeaadd__wwrriittee__aaddddrr
-
-
--ssiinnggllee__mmoodduullee
-
-
--ssttaattiicc
-
-
--ssuubb__lliibbrraarryy
-
-
--ssuubb__uummbbrreellllaa
-
-
--ttwwoolleevveell__nnaammeessppaaccee
-
-
--uummbbrreellllaa
-
-
--uunnddeeffiinneedd
-
-
--uunneexxppoorrtteedd__ssyymmbboollss__lliisstt
-
-
--wweeaakk__rreeffeerreennccee__mmiissmmaattcchheess
-
-
--wwhhaattssllooaaddeedd
These options are passed to the Darwin linker. The Darwin linker man page
-
describes them in detail.
_D_E_C _A_l_p_h_a _O_p_t_i_o_n_s
These --mm options are defined for the DEC Alpha implementations:
-
--mmnnoo--ssoofftt--ffllooaatt
-
-
--mmssoofftt--ffllooaatt
Use (do not use) the hardware floating-point instructions for
-
floating-point operations. When --mmssoofftt--ffllooaatt is specified,
functions in _l_i_b_g_c_c_._a will be used to perform floating-point
operations. Unless they are replaced by routines that emulate the
floating-point operations, or compiled in such a way as to call such
emulations routines, these routines will issue floating-point
operations. If you are compiling for an Alpha without floating-point
operations, you must ensure that the library is built so as not to call
them.
Note that Alpha implementations without floating-point operations are
required to have floating-point registers.
-
--mmffpp--rreegg
-
-
--mmnnoo--ffpp--rreeggss
Generate code that uses (does not use) the floating-point register set.
-
--mmnnoo--ffpp--rreeggss implies --mmssoofftt--ffllooaatt. If the floating-point
register set is not used, floating point operands are passed in integer
registers as if they were integers and floating-point results are passed
in $0 instead of $f0. This is a non-standard calling sequence,
so any function with a floating-point argument or return value called by code
compiled with --mmnnoo--ffpp--rreeggss must also be compiled with that
option.
A typical use of this option is building a kernel that does not use,
and hence need not save and restore, any floating-point registers.
-
--mmiieeeeee
The Alpha architecture implements floating-point hardware optimized for
-
maximum performance. It is mostly compliant with the IEEE floating
point standard. However, for full compliance, software assistance is
required. This option generates code fully IEEE compliant code
_e_x_c_e_p_t that the _i_n_e_x_a_c_t_-_f_l_a_g is not maintained (see below).
If this option is turned on, the preprocessor macro "_IEEE_FP" is
defined during compilation. The resulting code is less efficient but is
able to correctly support denormalized numbers and exceptional IEEE
values such as not-a-number and plus/minus infinity. Other Alpha
compilers call this option --iieeeeee__wwiitthh__nnoo__iinneexxaacctt.
-
--mmiieeeeee--wwiitthh--iinneexxaacctt
This is like --mmiieeeeee except the generated code also maintains
-
the IEEE _i_n_e_x_a_c_t_-_f_l_a_g. Turning on this option causes the
generated code to implement fully-compliant IEEE math. In addition to
"_IEEE_FP", "_IEEE_FP_EXACT" is defined as a preprocessor
macro. On some Alpha implementations the resulting code may execute
significantly slower than the code generated by default. Since there is
very little code that depends on the _i_n_e_x_a_c_t_-_f_l_a_g, you should
normally not specify this option. Other Alpha compilers call this
option --iieeeeee__wwiitthh__iinneexxaacctt.
-
--mmffpp--ttrraapp--mmooddee==_t_r_a_p_-_m_o_d_e
This option controls what floating-point related traps are enabled.
-
Other Alpha compilers call this option --ffppttmm _t_r_a_p_-_m_o_d_e.
The trap mode can be set to one of four values:
-
nn
This is the default (normal) setting. The only traps that are enabled
-
are the ones that cannot be disabled in software (e.g., division by zero
trap).
-
uu
In addition to the traps enabled by nn, underflow traps are enabled
-
as well.
-
ssuu
Like ssuu, but the instructions are marked to be safe for software
-
completion (see Alpha architecture manual for details).
-
ssuuii
Like ssuu, but inexact traps are enabled as well.
-
-
--mmffpp--rroouunnddiinngg--mmooddee==_r_o_u_n_d_i_n_g_-_m_o_d_e
Selects the IEEE rounding mode. Other Alpha compilers call this option
-
--ffpprrmm _r_o_u_n_d_i_n_g_-_m_o_d_e. The _r_o_u_n_d_i_n_g_-_m_o_d_e can be one
of:
-
nn
Normal IEEE rounding mode. Floating point numbers are rounded towards
-
the nearest machine number or towards the even machine number in case
of a tie.
-
mm
Round towards minus infinity.
-
-
cc
Chopped rounding mode. Floating point numbers are rounded towards zero.
-
-
dd
Dynamic rounding mode. A field in the floating point control register
-
(_f_p_c_r, see Alpha architecture reference manual) controls the
rounding mode in effect. The C library initializes this register for
rounding towards plus infinity. Thus, unless your program modifies the
_f_p_c_r, dd corresponds to round towards plus infinity.
-
--mmttrraapp--pprreecciissiioonn==_t_r_a_p_-_p_r_e_c_i_s_i_o_n
In the Alpha architecture, floating point traps are imprecise. This
-
means without software assistance it is impossible to recover from a
floating trap and program execution normally needs to be terminated.
GCC can generate code that can assist operating system trap handlers
in determining the exact location that caused a floating point trap.
Depending on the requirements of an application, different levels of
precisions can be selected:
-
pp
Program precision. This option is the default and means a trap handler
-
can only identify which program caused a floating point exception.
-
ff
Function precision. The trap handler can determine the function that
-
caused a floating point exception.
-
ii
Instruction precision. The trap handler can determine the exact
-
instruction that caused a floating point exception.
Other Alpha compilers provide the equivalent options called
--ssccooppee__ssaaffee and --rreessuummppttiioonn__ssaaffee.
-
--mmiieeeeee--ccoonnffoorrmmaanntt
This option marks the generated code as IEEE conformant. You must not
-
use this option unless you also specify --mmttrraapp--pprreecciissiioonn==ii and either
--mmffpp--ttrraapp--mmooddee==ssuu or --mmffpp--ttrraapp--mmooddee==ssuuii. Its only effect
is to emit the line ..eeffllaagg 4488 in the function prologue of the
generated assembly file. Under DEC Unix, this has the effect that
IEEE-conformant math library routines will be linked in.
-
--mmbbuuiilldd--ccoonnssttaannttss
Normally GCC examines a 32- or 64-bit integer constant to
-
see if it can construct it from smaller constants in two or three
instructions. If it cannot, it will output the constant as a literal and
generate code to load it from the data segment at runtime.
Use this option to require GCC to construct _a_l_l integer constants
using code, even if it takes more instructions (the maximum is six).
You would typically use this option to build a shared library dynamic
loader. Itself a shared library, it must relocate itself in memory
before it can find the variables and constants in its own data segment.
-
--mmaallpphhaa--aass
-
-
--mmggaass
Select whether to generate code to be assembled by the vendor-supplied
-
assembler (--mmaallpphhaa--aass) or by the GNU assembler --mmggaass.
-
--mmbbwwxx
-
-
--mmnnoo--bbwwxx
-
-
--mmcciixx
-
-
--mmnnoo--cciixx
-
-
--mmffiixx
-
-
--mmnnoo--ffiixx
-
-
--mmmmaaxx
-
-
--mmnnoo--mmaaxx
Indicate whether GCC should generate code to use the optional BWX,
-
CIX, FIX and MAX instruction sets. The default is to use the instruction
sets supported by the CPU type specified via --mmccppuu== option or that
of the CPU on which GCC was built if none was specified.
-
--mmffllooaatt--vvaaxx
-
-
--mmffllooaatt--iieeeeee
Generate code that uses (does not use) VAX F and G floating point
-
arithmetic instead of IEEE single and double precision.
-
--mmeexxpplliicciitt--rreellooccss
-
-
--mmnnoo--eexxpplliicciitt--rreellooccss
Older Alpha assemblers provided no way to generate symbol relocations
-
except via assembler macros. Use of these macros does not allow
optimal instruction scheduling. GNU binutils as of version 2.12
supports a new syntax that allows the compiler to explicitly mark
which relocations should apply to which instructions. This option
is mostly useful for debugging, as GCC detects the capabilities of
the assembler when it is built and sets the default accordingly.
-
--mmssmmaallll--ddaattaa
-
-
--mmllaarrggee--ddaattaa
When --mmeexxpplliicciitt--rreellooccss is in effect, static data is
-
accessed via _g_p_-_r_e_l_a_t_i_v_e relocations. When --mmssmmaallll--ddaattaa
is used, objects 8 bytes long or smaller are placed in a _s_m_a_l_l _d_a_t_a _a_r_e_a
(the ".sdata" and ".sbss" sections) and are accessed via
16-bit relocations off of the $gp register. This limits the
size of the small data area to 64KB, but allows the variables to be
directly accessed via a single instruction.
The default is --mmllaarrggee--ddaattaa. With this option the data area
is limited to just below 2GB. Programs that require more than 2GB of
data must use "malloc" or "mmap" to allocate the data in the
heap instead of in the program's data segment.
When generating code for shared libraries, --ffppiicc implies
--mmssmmaallll--ddaattaa and --ffPPIICC implies --mmllaarrggee--ddaattaa.
-
--mmssmmaallll--tteexxtt
-
-
--mmllaarrggee--tteexxtt
When --mmssmmaallll--tteexxtt is used, the compiler assumes that the
-
code of the entire program (or shared library) fits in 4MB, and is
thus reachable with a branch instruction. When --mmssmmaallll--ddaattaa
is used, the compiler can assume that all local symbols share the
same $gp value, and thus reduce the number of instructions
required for a function call from 4 to 1.
The default is --mmllaarrggee--tteexxtt.
-
--mmccppuu==_c_p_u___t_y_p_e
Set the instruction set and instruction scheduling parameters for
-
machine type _c_p_u___t_y_p_e. You can specify either the EEVV
style name or the corresponding chip number. GCC supports scheduling
parameters for the EV4, EV5 and EV6 family of processors and will
choose the default values for the instruction set from the processor
you specify. If you do not specify a processor type, GCC will default
to the processor on which the compiler was built.
Supported values for _c_p_u___t_y_p_e are
-
eevv44
-
-
eevv4455
-
-
2211006644
Schedules as an EV4 and has no instruction set extensions.
-
-
eevv55
-
-
2211116644
Schedules as an EV5 and has no instruction set extensions.
-
-
eevv5566
-
-
2211116644aa
Schedules as an EV5 and supports the BWX extension.
-
-
ppccaa5566
-
-
2211116644ppcc
-
-
2211116644PPCC
Schedules as an EV5 and supports the BWX and MAX extensions.
-
-
eevv66
-
-
2211226644
Schedules as an EV6 and supports the BWX, FIX, and MAX extensions.
-
-
eevv6677
-
-
2211226644aa
Schedules as an EV6 and supports the BWX, CIX, FIX, and MAX extensions.
-
-
--mmttuunnee==_c_p_u___t_y_p_e
Set only the instruction scheduling parameters for machine type
-
_c_p_u___t_y_p_e. The instruction set is not changed.
-
--mmmmeemmoorryy--llaatteennccyy==_t_i_m_e
Sets the latency the scheduler should assume for typical memory
-
references as seen by the application. This number is highly
dependent on the memory access patterns used by the application
and the size of the external cache on the machine.
Valid options for _t_i_m_e are
-
_n_u_m_b_e_r
A decimal number representing clock cycles.
-
-
LL11
-
-
LL22
-
-
LL33
-
-
mmaaiinn
The compiler contains estimates of the number of clock cycles for
-
"typical" EV4 & EV5 hardware for the Level 1, 2 & 3 caches
(also called Dcache, Scache, and Bcache), as well as to main memory.
Note that L3 is only valid for EV5.
_D_E_C _A_l_p_h_a_/_V_M_S _O_p_t_i_o_n_s
These --mm options are defined for the DEC Alpha/VMS implementations:
-
--mmvvmmss--rreettuurrnn--ccooddeess
Return VMS condition codes from main. The default is to return POSIX
-
style condition (e.g. error) codes.
_F_R_V _O_p_t_i_o_n_s
-
--mmggpprr--3322
Only use the first 32 general purpose registers.
-
-
--mmggpprr--6644
Use all 64 general purpose registers.
-
-
--mmffpprr--3322
Use only the first 32 floating point registers.
-
-
--mmffpprr--6644
Use all 64 floating point registers
-
-
--mmhhaarrdd--ffllooaatt
Use hardware instructions for floating point operations.
-
-
--mmssoofftt--ffllooaatt
Use library routines for floating point operations.
-
-
--mmaalllloocc--cccc
Dynamically allocate condition code registers.
-
-
--mmffiixxeedd--cccc
Do not try to dynamically allocate condition code registers, only
-
use "icc0" and "fcc0".
-
--mmddwwoorrdd
Change ABI to use double word insns.
-
-
--mmnnoo--ddwwoorrdd
Do not use double word instructions.
-
-
--mmddoouubbllee
Use floating point double instructions.
-
-
--mmnnoo--ddoouubbllee
Do not use floating point double instructions.
-
-
--mmmmeeddiiaa
Use media instructions.
-
-
--mmnnoo--mmeeddiiaa
Do not use media instructions.
-
-
--mmmmuullaadddd
Use multiply and add/subtract instructions.
-
-
--mmnnoo--mmuullaadddd
Do not use multiply and add/subtract instructions.
-
-
--mmffddppiicc
Select the FDPIC ABI, that uses function descriptors to represent
-
pointers to functions. Without any PIC/PIE-related options, it
implies --ffPPIIEE. With --ffppiicc or --ffppiiee, it
assumes GOT entries and small data are within a 12-bit range from the
GOT base address; with --ffPPIICC or --ffPPIIEE, GOT offsets
are computed with 32 bits.
-
--mmiinnlliinnee--pplltt
Enable inlining of PLT entries in function calls to functions that are
-
not known to bind locally. It has no effect without --mmffddppiicc.
It's enabled by default if optimizing for speed and compiling for
shared libraries (i.e., --ffPPIICC or --ffppiicc), or when an
optimization option such as --OO33 or above is present in the
command line.
-
--mmTTLLSS
Assume a large TLS segment when generating thread-local code.
-
-
--mmttllss
Do not assume a large TLS segment when generating thread-local code.
-
-
--mmggpprreell--rroo
Enable the use of "GPREL" relocations in the FDPIC ABI for data
-
that is known to be in read-only sections. It's enabled by default,
except for --ffppiicc or --ffppiiee: even though it may help
make the global offset table smaller, it trades 1 instruction for 4.
With --ffPPIICC or --ffPPIIEE, it trades 3 instructions for 4,
one of which may be shared by multiple symbols, and it avoids the need
for a GOT entry for the referenced symbol, so it's more likely to be a
win. If it is not, --mmnnoo--ggpprreell--rroo can be used to disable it.
-
--mmuullttiilliibb--lliibbrraarryy--ppiicc
Link with the (library, not FD) pic libraries. It's implied by
-
--mmlliibbrraarryy--ppiicc, as well as by --ffPPIICC and
--ffppiicc without --mmffddppiicc. You should never have to use
it explicitly.
-
--mmlliinnkkeedd--ffpp
Follow the EABI requirement of always creating a frame pointer whenever
-
a stack frame is allocated. This option is enabled by default and can
be disabled with --mmnnoo--lliinnkkeedd--ffpp.
-
--mmlloonngg--ccaallllss
Use indirect addressing to call functions outside the current
-
compilation unit. This allows the functions to be placed anywhere
within the 32-bit address space.
-
--mmaalliiggnn--llaabbeellss
Try to align labels to an 8-byte boundary by inserting nops into the
-
previous packet. This option only has an effect when VLIW packing
is enabled. It doesn't create new packets; it merely adds nops to
existing ones.
-
--mmlliibbrraarryy--ppiicc
Generate position-independent EABI code.
-
-
--mmaacccc--44
Use only the first four media accumulator registers.
-
-
--mmaacccc--88
Use all eight media accumulator registers.
-
-
--mmppaacckk
Pack VLIW instructions.
-
-
--mmnnoo--ppaacckk
Do not pack VLIW instructions.
-
-
--mmnnoo--eeffllaaggss
Do not mark ABI switches in e_flags.
-
-
--mmccoonndd--mmoovvee
Enable the use of conditional-move instructions (default).
-
This switch is mainly for debugging the compiler and will likely be removed
in a future version.
-
--mmnnoo--ccoonndd--mmoovvee
Disable the use of conditional-move instructions.
-
This switch is mainly for debugging the compiler and will likely be removed
in a future version.
-
--mmsscccc
Enable the use of conditional set instructions (default).
-
This switch is mainly for debugging the compiler and will likely be removed
in a future version.
-
--mmnnoo--sscccc
Disable the use of conditional set instructions.
-
This switch is mainly for debugging the compiler and will likely be removed
in a future version.
-
--mmccoonndd--eexxeecc
Enable the use of conditional execution (default).
-
This switch is mainly for debugging the compiler and will likely be removed
in a future version.
-
--mmnnoo--ccoonndd--eexxeecc
Disable the use of conditional execution.
-
This switch is mainly for debugging the compiler and will likely be removed
in a future version.
-
--mmvvlliiww--bbrraanncchh
Run a pass to pack branches into VLIW instructions (default).
-
This switch is mainly for debugging the compiler and will likely be removed
in a future version.
-
--mmnnoo--vvlliiww--bbrraanncchh
Do not run a pass to pack branches into VLIW instructions.
-
This switch is mainly for debugging the compiler and will likely be removed
in a future version.
-
--mmmmuullttii--ccoonndd--eexxeecc
Enable optimization of "&&" and "||" in conditional execution
-
(default).
This switch is mainly for debugging the compiler and will likely be removed
in a future version.
-
--mmnnoo--mmuullttii--ccoonndd--eexxeecc
Disable optimization of "&&" and "||" in conditional execution.
-
This switch is mainly for debugging the compiler and will likely be removed
in a future version.
-
--mmnneesstteedd--ccoonndd--eexxeecc
Enable nested conditional execution optimizations (default).
-
This switch is mainly for debugging the compiler and will likely be removed
in a future version.
-
--mmnnoo--nneesstteedd--ccoonndd--eexxeecc
Disable nested conditional execution optimizations.
-
This switch is mainly for debugging the compiler and will likely be removed
in a future version.
-
--mmooppttiimmiizzee--mmeemmbbaarr
This switch removes redundant "membar" instructions from the
-
compiler generated code. It is enabled by default.
-
--mmnnoo--ooppttiimmiizzee--mmeemmbbaarr
This switch disables the automatic removal of redundant "membar"
-
instructions from the generated code.
-
--mmttoommccaatt--ssttaattss
Cause gas to print out tomcat statistics.
-
-
--mmccppuu==_c_p_u
Select the processor type for which to generate code. Possible values are
-
ffrrvv, ffrr555500, ttoommccaatt, ffrr550000, ffrr445500,
ffrr440055, ffrr440000, ffrr330000 and ssiimmppllee.
_H_8_/_3_0_0 _O_p_t_i_o_n_s
These --mm options are defined for the H8/300 implementations:
-
--mmrreellaaxx
Shorten some address references at link time, when possible; uses the
-
linker option --rreellaaxx.
-
--mmhh
Generate code for the H8/300H.
-
-
--mmss
Generate code for the H8S.
-
-
--mmnn
Generate code for the H8S and H8/300H in the normal mode. This switch
-
must be used either with --mmhh or --mmss.
-
--mmss22660000
Generate code for the H8S/2600. This switch must be used with --mmss.
-
-
--mmiinntt3322
Make "int" data 32 bits by default.
-
-
--mmaalliiggnn--330000
On the H8/300H and H8S, use the same alignment rules as for the H8/300.
-
The default for the H8/300H and H8S is to align longs and floats on 4
byte boundaries.
--mmaalliiggnn--330000 causes them to be aligned on 2 byte boundaries.
This option has no effect on the H8/300.
_H_P_P_A _O_p_t_i_o_n_s
These --mm options are defined for the HPPA family of computers:
-
--mmaarrcchh==_a_r_c_h_i_t_e_c_t_u_r_e_-_t_y_p_e
Generate code for the specified architecture. The choices for
-
_a_r_c_h_i_t_e_c_t_u_r_e_-_t_y_p_e are 11..00 for PA 1.0, 11..11 for PA
1.1, and 22..00 for PA 2.0 processors. Refer to
_/_u_s_r_/_l_i_b_/_s_c_h_e_d_._m_o_d_e_l_s on an HP-UX system to determine the proper
architecture option for your machine. Code compiled for lower numbered
architectures will run on higher numbered architectures, but not the
other way around.
-
--mmppaa--rriisscc--11--00
-
-
--mmppaa--rriisscc--11--11
-
-
--mmppaa--rriisscc--22--00
Synonyms for --mmaarrcchh==11..00, --mmaarrcchh==11..11, and --mmaarrcchh==22..00 respectively.
-
-
--mmbbiigg--sswwiittcchh
Generate code suitable for big switch tables. Use this option only if
-
the assembler/linker complain about out of range branches within a switch
table.
-
--mmjjuummpp--iinn--ddeellaayy
Fill delay slots of function calls with unconditional jump instructions
-
by modifying the return pointer for the function call to be the target
of the conditional jump.
-
--mmddiissaabbllee--ffpprreeggss
Prevent floating point registers from being used in any manner. This is
-
necessary for compiling kernels which perform lazy context switching of
floating point registers. If you use this option and attempt to perform
floating point operations, the compiler will abort.
-
--mmddiissaabbllee--iinnddeexxiinngg
Prevent the compiler from using indexing address modes. This avoids some
-
rather obscure problems when compiling MIG generated code under MACH.
-
--mmnnoo--ssppaaccee--rreeggss
Generate code that assumes the target has no space registers. This allows
-
GCC to generate faster indirect calls and use unscaled index address modes.
Such code is suitable for level 0 PA systems and kernels.
-
--mmffaasstt--iinnddiirreecctt--ccaallllss
Generate code that assumes calls never cross space boundaries. This
-
allows GCC to emit code which performs faster indirect calls.
This option will not work in the presence of shared libraries or nested
functions.
-
--mmffiixxeedd--rraannggee==_r_e_g_i_s_t_e_r_-_r_a_n_g_e
Generate code treating the given register range as fixed registers.
-
A fixed register is one that the register allocator can not use. This is
useful when compiling kernel code. A register range is specified as
two registers separated by a dash. Multiple register ranges can be
specified separated by a comma.
-
--mmlloonngg--llooaadd--ssttoorree
Generate 3-instruction load and store sequences as sometimes required by
-
the HP-UX 10 linker. This is equivalent to the ++kk option to
the HP compilers.
-
--mmppoorrttaabbllee--rruunnttiimmee
Use the portable calling conventions proposed by HP for ELF systems.
-
-
--mmggaass
Enable the use of assembler directives only GAS understands.
-
-
--mmsscchheedduullee==_c_p_u_-_t_y_p_e
Schedule code according to the constraints for the machine type
-
_c_p_u_-_t_y_p_e. The choices for _c_p_u_-_t_y_p_e are 770000
77110000, 77110000LLCC, 77220000, 77330000 and 88000000. Refer
to _/_u_s_r_/_l_i_b_/_s_c_h_e_d_._m_o_d_e_l_s on an HP-UX system to determine the
proper scheduling option for your machine. The default scheduling is
88000000.
-
--mmlliinnkkeerr--oopptt
Enable the optimization pass in the HP-UX linker. Note this makes symbolic
-
debugging impossible. It also triggers a bug in the HP-UX 8 and HP-UX 9
linkers in which they give bogus error messages when linking some programs.
-
--mmssoofftt--ffllooaatt
Generate output containing library calls for floating point.
-
WWaarrnniinngg:: the requisite libraries are not available for all HPPA
targets. Normally the facilities of the machine's usual C compiler are
used, but this cannot be done directly in cross-compilation. You must make
your own arrangements to provide suitable library functions for
cross-compilation. The embedded target hhppppaa11..11--**--pprroo
does provide software floating point support.
--mmssoofftt--ffllooaatt changes the calling convention in the output file;
therefore, it is only useful if you compile _a_l_l of a program with
this option. In particular, you need to compile _l_i_b_g_c_c_._a, the
library that comes with GCC, with --mmssoofftt--ffllooaatt in order for
this to work.
-
--mmssiioo
Generate the predefine, "_SIO", for server IO. The default is
-
--mmwwssiioo. This generates the predefines, "__hp9000s700",
"__hp9000s700__" and "_WSIO", for workstation IO. These
options are available under HP-UX and HI-UX.
-
--mmggnnuu--lldd
Use GNU ld specific options. This passes --sshhaarreedd to ld when
-
building a shared library. It is the default when GCC is configured,
explicitly or implicitly, with the GNU linker. This option does not
have any affect on which ld is called, it only changes what parameters
are passed to that ld. The ld that is called is determined by the
----wwiitthh--lldd configure option, GCC's program search path, and
finally by the user's PPAATTHH. The linker used by GCC can be printed
using wwhhiicchh ``ggcccc --pprriinntt--pprroogg--nnaammee==lldd``. This option is only available
on the 64 bit HP-UX GCC, i.e. configured with hhppppaa**6644**--**--hhppuuxx**.
-
--mmhhpp--lldd
Use HP ld specific options. This passes --bb to ld when building
-
a shared library and passes ++AAcccceepptt TTyyppeeMMiissmmaattcchh to ld on all
links. It is the default when GCC is configured, explicitly or
implicitly, with the HP linker. This option does not have any affect on
which ld is called, it only changes what parameters are passed to that
ld. The ld that is called is determined by the ----wwiitthh--lldd
configure option, GCC's program search path, and finally by the user's
PPAATTHH. The linker used by GCC can be printed using wwhhiicchh
``ggcccc --pprriinntt--pprroogg--nnaammee==lldd``. This option is only available on the 64 bit
HP-UX GCC, i.e. configured with hhppppaa**6644**--**--hhppuuxx**.
-
--mmlloonngg--ccaallllss
Generate code that uses long call sequences. This ensures that a call
-
is always able to reach linker generated stubs. The default is to generate
long calls only when the distance from the call site to the beginning
of the function or translation unit, as the case may be, exceeds a
predefined limit set by the branch type being used. The limits for
normal calls are 7,600,000 and 240,000 bytes, respectively for the
PA 2.0 and PA 1.X architectures. Sibcalls are always limited at
240,000 bytes.
Distances are measured from the beginning of functions when using the
--ffffuunnccttiioonn--sseeccttiioonnss option, or when using the --mmggaass
and --mmnnoo--ppoorrttaabbllee--rruunnttiimmee options together under HP-UX with
the SOM linker.
It is normally not desirable to use this option as it will degrade
performance. However, it may be useful in large applications,
particularly when partial linking is used to build the application.
The types of long calls used depends on the capabilities of the
assembler and linker, and the type of code being generated. The
impact on systems that support long absolute calls, and long pic
symbol-difference or pc-relative calls should be relatively small.
However, an indirect call is used on 32-bit ELF systems in pic code
and it is quite long.
-
--mmuunniixx==_u_n_i_x_-_s_t_d
Generate compiler predefines and select a startfile for the specified
-
UNIX standard. The choices for _u_n_i_x_-_s_t_d are 9933, 9955
and 9988. 9933 is supported on all HP-UX versions. 9955
is available on HP-UX 10.10 and later. 9988 is available on HP-UX
11.11 and later. The default values are 9933 for HP-UX 10.00,
9955 for HP-UX 10.10 though to 11.00, and 9988 for HP-UX 11.11
and later.
--mmuunniixx==9933 provides the same predefines as GCC 3.3 and 3.4.
--mmuunniixx==9955 provides additional predefines for "XOPEN_UNIX"
and "_XOPEN_SOURCE_EXTENDED", and the startfile _u_n_i_x_9_5_._o.
--mmuunniixx==9988 provides additional predefines for "_XOPEN_UNIX",
"_XOPEN_SOURCE_EXTENDED", "_INCLUDE__STDC_A1_SOURCE" and
"_INCLUDE_XOPEN_SOURCE_500", and the startfile _u_n_i_x_9_8_._o.
It is _i_m_p_o_r_t_a_n_t to note that this option changes the interfaces
for various library routines. It also affects the operational behavior
of the C library. Thus, _e_x_t_r_e_m_e care is needed in using this
option.
Library code that is intended to operate with more than one UNIX
standard must test, set and restore the variable _____x_p_g_4___e_x_t_e_n_d_e_d___m_a_s_k
as appropriate. Most GNU software doesn't provide this capability.
-
--nnoolliibbddlldd
Suppress the generation of link options to search libdld.sl when the
-
--ssttaattiicc option is specified on HP-UX 10 and later.
-
--ssttaattiicc
The HP-UX implementation of setlocale in libc has a dependency on
-
libdld.sl. There isn't an archive version of libdld.sl. Thus,
when the --ssttaattiicc option is specified, special link options
are needed to resolve this dependency.
On HP-UX 10 and later, the GCC driver adds the necessary options to
link with libdld.sl when the --ssttaattiicc option is specified.
This causes the resulting binary to be dynamic. On the 64-bit port,
the linkers generate dynamic binaries by default in any case. The
--nnoolliibbddlldd option can be used to prevent the GCC driver from
adding these link options.
-
--tthhrreeaaddss
Add support for multithreading with the _d_c_e _t_h_r_e_a_d library
-
under HP-UX. This option sets flags for both the preprocessor and
linker.
_I_n_t_e_l _3_8_6 _a_n_d _A_M_D _x_8_6_-_6_4 _O_p_t_i_o_n_s
These --mm options are defined for the i386 and x86-64 family of
computers:
-
--mmttuunnee==_c_p_u_-_t_y_p_e
Tune to _c_p_u_-_t_y_p_e everything applicable about the generated code, except
-
for the ABI and the set of available instructions. The choices for
_c_p_u_-_t_y_p_e are:
-
_i_3_8_6
Original Intel's i386 CPU.
-
-
_i_4_8_6
Intel's i486 CPU. (No scheduling is implemented for this chip.)
-
-
_i_5_8_6_, _p_e_n_t_i_u_m
Intel Pentium CPU with no MMX support.
-
-
_p_e_n_t_i_u_m_-_m_m_x
Intel PentiumMMX CPU based on Pentium core with MMX instruction set support.
-
-
_i_6_8_6_, _p_e_n_t_i_u_m_p_r_o
Intel PentiumPro CPU.
-
-
_p_e_n_t_i_u_m_2
Intel Pentium2 CPU based on PentiumPro core with MMX instruction set support.
-
-
_p_e_n_t_i_u_m_3_, _p_e_n_t_i_u_m_3_m
Intel Pentium3 CPU based on PentiumPro core with MMX and SSE instruction set
-
support.
-
_p_e_n_t_i_u_m_-_m
Low power version of Intel Pentium3 CPU with MMX, SSE and SSE2 instruction set
-
support. Used by Centrino notebooks.
-
_p_e_n_t_i_u_m_4_, _p_e_n_t_i_u_m_4_m
Intel Pentium4 CPU with MMX, SSE and SSE2 instruction set support.
-
-
_p_r_e_s_c_o_t_t
Improved version of Intel Pentium4 CPU with MMX, SSE, SSE2 and SSE3 instruction
-
set support.
-
_n_o_c_o_n_a
Improved version of Intel Pentium4 CPU with 64-bit extensions, MMX, SSE,
-
SSE2 and SSE3 instruction set support.
-
_k_6
AMD K6 CPU with MMX instruction set support.
-
-
_k_6_-_2_, _k_6_-_3
Improved versions of AMD K6 CPU with MMX and 3dNOW! instruction set support.
-
-
_a_t_h_l_o_n_, _a_t_h_l_o_n_-_t_b_i_r_d
AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and SSE prefetch instructions
-
support.
-
_a_t_h_l_o_n_-_4_, _a_t_h_l_o_n_-_x_p_, _a_t_h_l_o_n_-_m_p
Improved AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and full SSE
-
instruction set support.
-
_k_8_, _o_p_t_e_r_o_n_, _a_t_h_l_o_n_6_4_, _a_t_h_l_o_n_-_f_x
AMD K8 core based CPUs with x86-64 instruction set support. (This supersets
-
MMX, SSE, SSE2, 3dNOW!, enhanced 3dNOW! and 64-bit instruction set extensions.)
-
_w_i_n_c_h_i_p_-_c_6
IDT Winchip C6 CPU, dealt in same way as i486 with additional MMX instruction
-
set support.
-
_w_i_n_c_h_i_p_2
IDT Winchip2 CPU, dealt in same way as i486 with additional MMX and 3dNOW!
-
instruction set support.
-
_c_3
Via C3 CPU with MMX and 3dNOW! instruction set support. (No scheduling is
-
implemented for this chip.)
-
_c_3_-_2
Via C3-2 CPU with MMX and SSE instruction set support. (No scheduling is
-
implemented for this chip.)
While picking a specific _c_p_u_-_t_y_p_e will schedule things appropriately
for that particular chip, the compiler will not generate any code that
does not run on the i386 without the --mmaarrcchh==_c_p_u_-_t_y_p_e option
being used.
-
--mmaarrcchh==_c_p_u_-_t_y_p_e
Generate instructions for the machine type _c_p_u_-_t_y_p_e. The choices
-
for _c_p_u_-_t_y_p_e are the same as for --mmttuunnee. Moreover,
specifying --mmaarrcchh==_c_p_u_-_t_y_p_e implies --mmttuunnee==_c_p_u_-_t_y_p_e.
-
--mmccppuu==_c_p_u_-_t_y_p_e
A deprecated synonym for --mmttuunnee.
-
-
--mm338866
-
-
--mm448866
-
-
--mmppeennttiiuumm
-
-
--mmppeennttiiuummpprroo
These options are synonyms for --mmttuunnee==ii338866, --mmttuunnee==ii448866,
-
--mmttuunnee==ppeennttiiuumm, and --mmttuunnee==ppeennttiiuummpprroo respectively.
These synonyms are deprecated.
-
--mmffppmmaatthh==_u_n_i_t
Generate floating point arithmetics for selected unit _u_n_i_t. The choices
-
for _u_n_i_t are:
-
338877
Use the standard 387 floating point coprocessor present majority of chips and
-
emulated otherwise. Code compiled with this option will run almost everywhere.
The temporary results are computed in 80bit precision instead of precision
specified by the type resulting in slightly different results compared to most
of other chips. See --ffffllooaatt--ssttoorree for more detailed description.
This is the default choice for i386 compiler.
-
ssssee
Use scalar floating point instructions present in the SSE instruction set.
-
This instruction set is supported by Pentium3 and newer chips, in the AMD line
by Athlon-4, Athlon-xp and Athlon-mp chips. The earlier version of SSE
instruction set supports only single precision arithmetics, thus the double and
extended precision arithmetics is still done using 387. Later version, present
only in Pentium4 and the future AMD x86-64 chips supports double precision
arithmetics too.
For the i386 compiler, you need to use --mmaarrcchh==_c_p_u_-_t_y_p_e, --mmssssee
or --mmssssee22 switches to enable SSE extensions and make this option
effective. For the x86-64 compiler, these extensions are enabled by default.
The resulting code should be considerably faster in the majority of cases and avoid
the numerical instability problems of 387 code, but may break some existing
code that expects temporaries to be 80bit.
This is the default choice for the x86-64 compiler.
-
ssssee,,338877
Attempt to utilize both instruction sets at once. This effectively double the
-
amount of available registers and on chips with separate execution units for
387 and SSE the execution resources too. Use this option with care, as it is
still experimental, because the GCC register allocator does not model separate
functional units well resulting in instable performance.
-
--mmaassmm==_d_i_a_l_e_c_t
Output asm instructions using selected _d_i_a_l_e_c_t. Supported
-
choices are iinntteell or aatttt (the default one). Darwin does
not support iinntteell.
-
--mmiieeeeee--ffpp
-
-
--mmnnoo--iieeeeee--ffpp
Control whether or not the compiler uses IEEE floating point
-
comparisons. These handle correctly the case where the result of a
comparison is unordered.
-
--mmssoofftt--ffllooaatt
Generate output containing library calls for floating point.
-
WWaarrnniinngg:: the requisite libraries are not part of GCC.
Normally the facilities of the machine's usual C compiler are used, but
this can't be done directly in cross-compilation. You must make your
own arrangements to provide suitable library functions for
cross-compilation.
On machines where a function returns floating point results in the 80387
register stack, some floating point opcodes may be emitted even if
--mmssoofftt--ffllooaatt is used.
-
--mmnnoo--ffpp--rreett--iinn--338877
Do not use the FPU registers for return values of functions.
-
The usual calling convention has functions return values of types
"float" and "double" in an FPU register, even if there
is no FPU. The idea is that the operating system should emulate
an FPU.
The option --mmnnoo--ffpp--rreett--iinn--338877 causes such values to be returned
in ordinary CPU registers instead.
-
--mmnnoo--ffaannccyy--mmaatthh--338877
Some 387 emulators do not support the "sin", "cos" and
-
"sqrt" instructions for the 387. Specify this option to avoid
generating those instructions. This option is the default on FreeBSD,
OpenBSD and NetBSD. This option is overridden when --mmaarrcchh
indicates that the target cpu will always have an FPU and so the
instruction will not need emulation. As of revision 2.6.1, these
instructions are not generated unless you also use the
--ffuunnssaaffee--mmaatthh--ooppttiimmiizzaattiioonnss switch.
-
--mmaalliiggnn--ddoouubbllee
-
-
--mmnnoo--aalliiggnn--ddoouubbllee
Control whether GCC aligns "double", "long double", and
-
"long long" variables on a two word boundary or a one word
boundary. Aligning "double" variables on a two word boundary will
produce code that runs somewhat faster on a PPeennttiiuumm at the
expense of more memory.
WWaarrnniinngg:: if you use the --mmaalliiggnn--ddoouubbllee switch,
structures containing the above types will be aligned differently than
the published application binary interface specifications for the 386
and will not be binary compatible with structures in code compiled
without that switch.
-
--mm9966bbiitt--lloonngg--ddoouubbllee
-
-
--mm112288bbiitt--lloonngg--ddoouubbllee
These switches control the size of "long double" type. The i386
-
application binary interface specifies the size to be 96 bits,
so --mm9966bbiitt--lloonngg--ddoouubbllee is the default in 32 bit mode.
Modern architectures (Pentium and newer) would prefer "long double"
to be aligned to an 8 or 16 byte boundary. In arrays or structures
conforming to the ABI, this would not be possible. So specifying a
--mm112288bbiitt--lloonngg--ddoouubbllee will align "long double"
to a 16 byte boundary by padding the "long double" with an additional
32 bit zero.
In the x86-64 compiler, --mm112288bbiitt--lloonngg--ddoouubbllee is the default choice as
its ABI specifies that "long double" is to be aligned on 16 byte boundary.
Notice that neither of these options enable any extra precision over the x87
standard of 80 bits for a "long double".
WWaarrnniinngg:: if you override the default value for your target ABI, the
structures and arrays containing "long double" variables will change
their size as well as function calling convention for function taking
"long double" will be modified. Hence they will not be binary
compatible with arrays or structures in code compiled without that switch.
-
--mmmmllaarrggee--ddaattaa--tthhrreesshhoolldd==_n_u_m_b_e_r
When --mmccmmooddeell==mmeeddiiuumm is specified, the data greater than
-
_t_h_r_e_s_h_o_l_d are placed in large data section. This value must be the
same across all object linked into the binary and defaults to 65535.
-
--mmssvvrr33--sshhlliibb
-
-
--mmnnoo--ssvvrr33--sshhlliibb
Control whether GCC places uninitialized local variables into the
-
"bss" or "data" segments. --mmssvvrr33--sshhlliibb places them
into "bss". These options are meaningful only on System V Release 3.
-
--mmrrttdd
Use a different function-calling convention, in which functions that
-
take a fixed number of arguments return with the "ret" _n_u_m
instruction, which pops their arguments while returning. This saves one
instruction in the caller since there is no need to pop the arguments
there.
You can specify that an individual function is called with this calling
sequence with the function attribute ssttddccaallll. You can also
override the --mmrrttdd option by using the function attribute
ccddeeccll.
WWaarrnniinngg:: this calling convention is incompatible with the one
normally used on Unix, so you cannot use it if you need to call
libraries compiled with the Unix compiler.
Also, you must provide function prototypes for all functions that
take variable numbers of arguments (including "printf");
otherwise incorrect code will be generated for calls to those
functions.
In addition, seriously incorrect code will result if you call a
function with too many arguments. (Normally, extra arguments are
harmlessly ignored.)
-
--mmrreeggppaarrmm==_n_u_m
Control how many registers are used to pass integer arguments. By
-
default, no registers are used to pass arguments, and at most 3
registers can be used. You can control this behavior for a specific
function by using the function attribute rreeggppaarrmm.
WWaarrnniinngg:: if you use this switch, and
_n_u_m is nonzero, then you must build all modules with the same
value, including any libraries. This includes the system libraries and
startup modules.
-
--mmsssseerreeggppaarrmm
Use SSE register passing conventions for float and double arguments
-
and return values. You can control this behavior for a specific
function by using the function attribute sssseerreeggppaarrmm.
WWaarrnniinngg:: if you use this switch then you must build all
modules with the same value, including any libraries. This includes
the system libraries and startup modules.
-
--mmpprreeffeerrrreedd--ssttaacckk--bboouunnddaarryy==_n_u_m
Attempt to keep the stack boundary aligned to a 2 raised to _n_u_m
-
byte boundary. If --mmpprreeffeerrrreedd--ssttaacckk--bboouunnddaarryy is not specified,
the default is 4 (16 bytes or 128 bits), except when optimizing for code
size (--OOss), in which case the default is the minimum correct
alignment (4 bytes for x86, and 8 bytes for x86-64).
On Pentium and PentiumPro, "double" and "long double" values
should be aligned to an 8 byte boundary (see --mmaalliiggnn--ddoouubbllee) or
suffer significant run time performance penalties. On Pentium III, the
Streaming SIMD Extension (SSE) data type "__m128" suffers similar
penalties if it is not 16 byte aligned.
To ensure proper alignment of this values on the stack, the stack boundary
must be as aligned as that required by any value stored on the stack.
Further, every function must be generated such that it keeps the stack
aligned. Thus calling a function compiled with a higher preferred
stack boundary from a function compiled with a lower preferred stack
boundary will most likely misalign the stack. It is recommended that
libraries that use callbacks always use the default setting.
This extra alignment does consume extra stack space, and generally
increases code size. Code that is sensitive to stack space usage, such
as embedded systems and operating system kernels, may want to reduce the
preferred alignment to --mmpprreeffeerrrreedd--ssttaacckk--bboouunnddaarryy==22.
-
--mmmmmmxx
-
-
--mmnnoo--mmmmxx
-
-
--mmssssee
-
-
--mmnnoo--ssssee
-
-
--mmssssee22
-
-
--mmnnoo--ssssee22
-
-
--mmssssee33
-
-
--mmnnoo--ssssee33
-
-
--mm33ddnnooww
-
-
--mmnnoo--33ddnnooww
These switches enable or disable the use of instructions in the MMX,
-
SSE, SSE2 or 3DNow! extended instruction sets. These extensions are
also available as built-in functions: see XX8866 BBuuiilltt--iinn FFuunnccttiioonnss,
for details of the functions enabled and disabled by these switches.
To have SSE/SSE2 instructions generated automatically from floating-point
code (as opposed to 387 instructions), see --mmffppmmaatthh==ssssee.
These options will enable GCC to use these extended instructions in
generated code, even without --mmffppmmaatthh==ssssee. Applications which
perform runtime CPU detection must compile separate files for each
supported architecture, using the appropriate flags. In particular,
the file containing the CPU detection code should be compiled without
these options.
-
--mmppuusshh--aarrggss
-
-
--mmnnoo--ppuusshh--aarrggss
Use PUSH operations to store outgoing parameters. This method is shorter
-
and usually equally fast as method using SUB/MOV operations and is enabled
by default. In some cases disabling it may improve performance because of
improved scheduling and reduced dependencies.
-
--mmaaccccuummuullaattee--oouuttggooiinngg--aarrggss
If enabled, the maximum amount of space required for outgoing arguments will be
-
computed in the function prologue. This is faster on most modern CPUs
because of reduced dependencies, improved scheduling and reduced stack usage
when preferred stack boundary is not equal to 2. The drawback is a notable
increase in code size. This switch implies --mmnnoo--ppuusshh--aarrggss.
-
--mmtthhrreeaaddss
Support thread-safe exception handling on MMiinnggww3322. Code that relies
-
on thread-safe exception handling must compile and link all code with the
--mmtthhrreeaaddss option. When compiling, --mmtthhrreeaaddss defines
--DD__MMTT; when linking, it links in a special thread helper library
--llmmiinnggwwtthhrrdd which cleans up per thread exception handling data.
-
--mmnnoo--aalliiggnn--ssttrriinnggooppss
Do not align destination of inlined string operations. This switch reduces
-
code size and improves performance in case the destination is already aligned,
but GCC doesn't know about it.
-
--mmiinnlliinnee--aallll--ssttrriinnggooppss
By default GCC inlines string operations only when destination is known to be
-
aligned at least to 4 byte boundary. This enables more inlining, increase code
size, but may improve performance of code that depends on fast memcpy, strlen
and memset for short lengths.
-
--mmoommiitt--lleeaaff--ffrraammee--ppooiinntteerr
Don't keep the frame pointer in a register for leaf functions. This
-
avoids the instructions to save, set up and restore frame pointers and
makes an extra register available in leaf functions. The option
--ffoommiitt--ffrraammee--ppooiinntteerr removes the frame pointer for all functions
which might make debugging harder.
-
--mmttllss--ddiirreecctt--sseegg--rreeffss
-
-
--mmnnoo--ttllss--ddiirreecctt--sseegg--rreeffss
Controls whether TLS variables may be accessed with offsets from the
-
TLS segment register (%gs for 32-bit, %fs for 64-bit),
or whether the thread base pointer must be added. Whether or not this
is legal depends on the operating system, and whether it maps the
segment to cover the entire TLS area.
For systems that use GNU libc, the default is on.
These --mm switches are supported in addition to the above
on AMD x86-64 processors in 64-bit environments.
-
--mm3322
-
-
--mm6644
Generate code for a 32-bit or 64-bit environment.
-
The 32-bit environment sets int, long and pointer to 32 bits and
generates code that runs on any i386 system.
The 64-bit environment sets int to 32 bits and long and pointer
to 64 bits and generates code for AMD's x86-64 architecture.
-
--mmnnoo--rreedd--zzoonnee
Do not use a so called red zone for x86-64 code. The red zone is mandated
-
by the x86-64 ABI, it is a 128-byte area beyond the location of the
stack pointer that will not be modified by signal or interrupt handlers
and therefore can be used for temporary data without adjusting the stack
pointer. The flag --mmnnoo--rreedd--zzoonnee disables this red zone.
-
--mmccmmooddeell==ssmmaallll
Generate code for the small code model: the program and its symbols must
-
be linked in the lower 2 GB of the address space. Pointers are 64 bits.
Programs can be statically or dynamically linked. This is the default
code model.
-
--mmccmmooddeell==kkeerrnneell
Generate code for the kernel code model. The kernel runs in the
-
negative 2 GB of the address space.
This model has to be used for Linux kernel code.
-
--mmccmmooddeell==mmeeddiiuumm
Generate code for the medium model: The program is linked in the lower 2
-
GB of the address space but symbols can be located anywhere in the
address space. Programs can be statically or dynamically linked, but
building of shared libraries are not supported with the medium model.
-
--mmccmmooddeell==llaarrggee
Generate code for the large model: This model makes no assumptions
-
about addresses and sizes of sections. Currently GCC does not implement
this model.
_I_A_-_6_4 _O_p_t_i_o_n_s
These are the --mm options defined for the Intel IA-64 architecture.
-
--mmbbiigg--eennddiiaann
Generate code for a big endian target. This is the default for HP-UX.
-
-
--mmlliittttllee--eennddiiaann
Generate code for a little endian target. This is the default for AIX5
-
and GNU/Linux.
-
--mmggnnuu--aass
-
-
--mmnnoo--ggnnuu--aass
Generate (or don't) code for the GNU assembler. This is the default.
-
-
--mmggnnuu--lldd
-
-
--mmnnoo--ggnnuu--lldd
Generate (or don't) code for the GNU linker. This is the default.
-
-
--mmnnoo--ppiicc
Generate code that does not use a global pointer register. The result
-
is not position independent code, and violates the IA-64 ABI.
-
--mmvvoollaattiillee--aassmm--ssttoopp
-
-
--mmnnoo--vvoollaattiillee--aassmm--ssttoopp
Generate (or don't) a stop bit immediately before and after volatile asm
-
statements.
-
--mmrreeggiisstteerr--nnaammeess
-
-
--mmnnoo--rreeggiisstteerr--nnaammeess
Generate (or don't) iinn, lloocc, and oouutt register names for
-
the stacked registers. This may make assembler output more readable.
-
--mmnnoo--ssddaattaa
-
-
--mmssddaattaa
Disable (or enable) optimizations that use the small data section. This may
-
be useful for working around optimizer bugs.
-
--mmccoonnssttaanntt--ggpp
Generate code that uses a single constant global pointer value. This is
-
useful when compiling kernel code.
-
--mmaauuttoo--ppiicc
Generate code that is self-relocatable. This implies --mmccoonnssttaanntt--ggpp.
-
This is useful when compiling firmware code.
-
--mmiinnlliinnee--ffllooaatt--ddiivviiddee--mmiinn--llaatteennccyy
Generate code for inline divides of floating point values
-
using the minimum latency algorithm.
-
--mmiinnlliinnee--ffllooaatt--ddiivviiddee--mmaaxx--tthhrroouugghhppuutt
Generate code for inline divides of floating point values
-
using the maximum throughput algorithm.
-
--mmiinnlliinnee--iinntt--ddiivviiddee--mmiinn--llaatteennccyy
Generate code for inline divides of integer values
-
using the minimum latency algorithm.
-
--mmiinnlliinnee--iinntt--ddiivviiddee--mmaaxx--tthhrroouugghhppuutt
Generate code for inline divides of integer values
-
using the maximum throughput algorithm.
-
--mmiinnlliinnee--ssqqrrtt--mmiinn--llaatteennccyy
Generate code for inline square roots
-
using the minimum latency algorithm.
-
--mmiinnlliinnee--ssqqrrtt--mmaaxx--tthhrroouugghhppuutt
Generate code for inline square roots
-
using the maximum throughput algorithm.
-
--mmnnoo--ddwwaarrff22--aassmm
-
-
--mmddwwaarrff22--aassmm
Don't (or do) generate assembler code for the DWARF2 line number debugging
-
info. This may be useful when not using the GNU assembler.
-
--mmeeaarrllyy--ssttoopp--bbiittss
-
-
--mmnnoo--eeaarrllyy--ssttoopp--bbiittss
Allow stop bits to be placed earlier than immediately preceding the
-
instruction that triggered the stop bit. This can improve instruction
scheduling, but does not always do so.
-
--mmffiixxeedd--rraannggee==_r_e_g_i_s_t_e_r_-_r_a_n_g_e
Generate code treating the given register range as fixed registers.
-
A fixed register is one that the register allocator can not use. This is
useful when compiling kernel code. A register range is specified as
two registers separated by a dash. Multiple register ranges can be
specified separated by a comma.
-
--mmttllss--ssiizzee==_t_l_s_-_s_i_z_e
Specify bit size of immediate TLS offsets. Valid values are 14, 22, and
-
64.
-
--mmttuunnee==_c_p_u_-_t_y_p_e
Tune the instruction scheduling for a particular CPU, Valid values are
-
itanium, itanium1, merced, itanium2, and mckinley.
-
--mmtt
-
-
--pptthhrreeaadd
Add support for multithreading using the POSIX threads library. This
-
option sets flags for both the preprocessor and linker. It does
not affect the thread safety of object code produced by the compiler or
that of libraries supplied with it. These are HP-UX specific flags.
-
--mmiillpp3322
-
-
--mmllpp6644
Generate code for a 32-bit or 64-bit environment.
-
The 32-bit environment sets int, long and pointer to 32 bits.
The 64-bit environment sets int to 32 bits and long and pointer
to 64 bits. These are HP-UX specific flags.
_M_3_2_C _O_p_t_i_o_n_s
-
--mmccppuu==_n_a_m_e
Select the CPU for which code is generated. _n_a_m_e may be one of
-
rr88cc for the R8C/Tiny series, mm1166cc for the M16C (up to
/60) series, mm3322ccmm for the M16C/80 series, or mm3322cc for
the M32C/80 series.
-
--mmssiimm
Specifies that the program will be run on the simulator. This causes
-
an alternate runtime library to be linked in which supports, for
example, file I/O. You must not use this option when generating
programs that will run on real hardware; you must provide your own
runtime library for whatever I/O functions are needed.
-
--mmeemmrreeggss==_n_u_m_b_e_r
Specifies the number of memory-based pseudo-registers GCC will use
-
during code generation. These pseudo-registers will be used like real
registers, so there is a tradeoff between GCC's ability to fit the
code into available registers, and the performance penalty of using
memory instead of registers. Note that all modules in a program must
be compiled with the same value for this option. Because of that, you
must not use this option with the default runtime libraries gcc
builds.
_M_3_2_R_/_D _O_p_t_i_o_n_s
These --mm options are defined for Renesas M32R/D architectures:
-
--mm3322rr22
Generate code for the M32R/2.
-
-
--mm3322rrxx
Generate code for the M32R/X.
-
-
--mm3322rr
Generate code for the M32R. This is the default.
-
-
--mmmmooddeell==ssmmaallll
Assume all objects live in the lower 16MB of memory (so that their addresses
-
can be loaded with the "ld24" instruction), and assume all subroutines
are reachable with the "bl" instruction.
This is the default.
The addressability of a particular object can be set with the
"model" attribute.
-
--mmmmooddeell==mmeeddiiuumm
Assume objects may be anywhere in the 32-bit address space (the compiler
-
will generate "seth/add3" instructions to load their addresses), and
assume all subroutines are reachable with the "bl" instruction.
-
--mmmmooddeell==llaarrggee
Assume objects may be anywhere in the 32-bit address space (the compiler
-
will generate "seth/add3" instructions to load their addresses), and
assume subroutines may not be reachable with the "bl" instruction
(the compiler will generate the much slower "seth/add3/jl"
instruction sequence).
-
--mmssddaattaa==nnoonnee
Disable use of the small data area. Variables will be put into
-
one of ..ddaattaa, bbssss, or ..rrooddaattaa (unless the
"section" attribute has been specified).
This is the default.
The small data area consists of sections ..ssddaattaa and ..ssbbssss.
Objects may be explicitly put in the small data area with the
"section" attribute using one of these sections.
-
--mmssddaattaa==ssddaattaa
Put small global and static data in the small data area, but do not
-
generate special code to reference them.
-
--mmssddaattaa==uussee
Put small global and static data in the small data area, and generate
-
special instructions to reference them.
-
--GG _n_u_m
Put global and static objects less than or equal to _n_u_m bytes
-
into the small data or bss sections instead of the normal data or bss
sections. The default value of _n_u_m is 8.
The --mmssddaattaa option must be set to one of ssddaattaa or uussee
for this option to have any effect.
All modules should be compiled with the same --GG _n_u_m value.
Compiling with different values of _n_u_m may or may not work; if it
doesn't the linker will give an error message---incorrect code will not be
generated.
-
--mmddeebbuugg
Makes the M32R specific code in the compiler display some statistics
-
that might help in debugging programs.
-
--mmaalliiggnn--llooooppss
Align all loops to a 32-byte boundary.
-
-
--mmnnoo--aalliiggnn--llooooppss
Do not enforce a 32-byte alignment for loops. This is the default.
-
-
--mmiissssuuee--rraattee==_n_u_m_b_e_r
Issue _n_u_m_b_e_r instructions per cycle. _n_u_m_b_e_r can only be 1
-
or 2.
-
--mmbbrraanncchh--ccoosstt==_n_u_m_b_e_r
_n_u_m_b_e_r can only be 1 or 2. If it is 1 then branches will be
-
preferred over conditional code, if it is 2, then the opposite will
apply.
-
--mmfflluusshh--ttrraapp==_n_u_m_b_e_r
Specifies the trap number to use to flush the cache. The default is
-
12. Valid numbers are between 0 and 15 inclusive.
-
--mmnnoo--fflluusshh--ttrraapp
Specifies that the cache cannot be flushed by using a trap.
-
-
--mmfflluusshh--ffuunncc==_n_a_m_e
Specifies the name of the operating system function to call to flush
-
the cache. The default is ___f_l_u_s_h___c_a_c_h_e, but a function call
will only be used if a trap is not available.
-
--mmnnoo--fflluusshh--ffuunncc
Indicates that there is no OS function for flushing the cache.
-
_M_6_8_0_x_0 _O_p_t_i_o_n_s
These are the --mm options defined for the 68000 series. The default
values for these options depends on which style of 68000 was selected when
the compiler was configured; the defaults for the most common choices are
given below.
-
--mm6688000000
-
-
--mmcc6688000000
Generate output for a 68000. This is the default
-
when the compiler is configured for 68000-based systems.
Use this option for microcontrollers with a 68000 or EC000 core,
including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356.
-
--mm6688002200
-
-
--mmcc6688002200
Generate output for a 68020. This is the default
-
when the compiler is configured for 68020-based systems.
-
--mm6688888811
Generate output containing 68881 instructions for floating point.
-
This is the default for most 68020 systems unless ----nnffpp was
specified when the compiler was configured.
-
--mm6688003300
Generate output for a 68030. This is the default when the compiler is
-
configured for 68030-based systems.
-
--mm6688004400
Generate output for a 68040. This is the default when the compiler is
-
configured for 68040-based systems.
This option inhibits the use of 68881/68882 instructions that have to be
emulated by software on the 68040. Use this option if your 68040 does not
have code to emulate those instructions.
-
--mm6688006600
Generate output for a 68060. This is the default when the compiler is
-
configured for 68060-based systems.
This option inhibits the use of 68020 and 68881/68882 instructions that
have to be emulated by software on the 68060. Use this option if your 68060
does not have code to emulate those instructions.
-
--mmccppuu3322
Generate output for a CPU32. This is the default
-
when the compiler is configured for CPU32-based systems.
Use this option for microcontrollers with a
CPU32 or CPU32+ core, including the 68330, 68331, 68332, 68333, 68334,
68336, 68340, 68341, 68349 and 68360.
-
--mm55220000
Generate output for a 520X "coldfire" family cpu. This is the default
-
when the compiler is configured for 520X-based systems.
Use this option for microcontroller with a 5200 core, including
the MCF5202, MCF5203, MCF5204 and MCF5202.
-
--mm6688002200--4400
Generate output for a 68040, without using any of the new instructions.
-
This results in code which can run relatively efficiently on either a
68020/68881 or a 68030 or a 68040. The generated code does use the
68881 instructions that are emulated on the 68040.
-
--mm6688002200--6600
Generate output for a 68060, without using any of the new instructions.
-
This results in code which can run relatively efficiently on either a
68020/68881 or a 68030 or a 68040. The generated code does use the
68881 instructions that are emulated on the 68060.
-
--mmssoofftt--ffllooaatt
Generate output containing library calls for floating point.
-
WWaarrnniinngg:: the requisite libraries are not available for all m68k
targets. Normally the facilities of the machine's usual C compiler are
used, but this can't be done directly in cross-compilation. You must
make your own arrangements to provide suitable library functions for
cross-compilation. The embedded targets mm6688kk--**--aaoouutt and
mm6688kk--**--ccooffff do provide software floating point support.
-
--mmsshhoorrtt
Consider type "int" to be 16 bits wide, like "short int".
-
Additionally, parameters passed on the stack are also aligned to a
16-bit boundary even on targets whose API mandates promotion to 32-bit.
-
--mmnnoobbiittffiieelldd
Do not use the bit-field instructions. The --mm6688000000, --mmccppuu3322
-
and --mm55220000 options imply --mmnnoobbiittffiieelldd.
-
--mmbbiittffiieelldd
Do use the bit-field instructions. The --mm6688002200 option implies
-
--mmbbiittffiieelldd. This is the default if you use a configuration
designed for a 68020.
-
--mmrrttdd
Use a different function-calling convention, in which functions
-
that take a fixed number of arguments return with the "rtd"
instruction, which pops their arguments while returning. This
saves one instruction in the caller since there is no need to pop
the arguments there.
This calling convention is incompatible with the one normally
used on Unix, so you cannot use it if you need to call libraries
compiled with the Unix compiler.
Also, you must provide function prototypes for all functions that
take variable numbers of arguments (including "printf");
otherwise incorrect code will be generated for calls to those
functions.
In addition, seriously incorrect code will result if you call a
function with too many arguments. (Normally, extra arguments are
harmlessly ignored.)
The "rtd" instruction is supported by the 68010, 68020, 68030,
68040, 68060 and CPU32 processors, but not by the 68000 or 5200.
-
--mmaalliiggnn--iinntt
-
-
--mmnnoo--aalliiggnn--iinntt
Control whether GCC aligns "int", "long", "long long",
-
"float", "double", and "long double" variables on a 32-bit
boundary (--mmaalliiggnn--iinntt) or a 16-bit boundary (--mmnnoo--aalliiggnn--iinntt).
Aligning variables on 32-bit boundaries produces code that runs somewhat
faster on processors with 32-bit busses at the expense of more memory.
WWaarrnniinngg:: if you use the --mmaalliiggnn--iinntt switch, GCC will
align structures containing the above types differently than
most published application binary interface specifications for the m68k.
-
--mmppccrreell
Use the pc-relative addressing mode of the 68000 directly, instead of
-
using a global offset table. At present, this option implies --ffppiicc,
allowing at most a 16-bit offset for pc-relative addressing. --ffPPIICC is
not presently supported with --mmppccrreell, though this could be supported for
68020 and higher processors.
-
--mmnnoo--ssttrriicctt--aalliiggnn
-
-
--mmssttrriicctt--aalliiggnn
Do not (do) assume that unaligned memory references will be handled by
-
the system.
-
--mmsseepp--ddaattaa
Generate code that allows the data segment to be located in a different
-
area of memory from the text segment. This allows for execute in place in
an environment without virtual memory management. This option implies
--ffPPIICC.
-
--mmnnoo--sseepp--ddaattaa
Generate code that assumes that the data segment follows the text segment.
-
This is the default.
-
--mmiidd--sshhaarreedd--lliibbrraarryy
Generate code that supports shared libraries via the library ID method.
-
This allows for execute in place and shared libraries in an environment
without virtual memory management. This option implies --ffPPIICC.
-
--mmnnoo--iidd--sshhaarreedd--lliibbrraarryy
Generate code that doesn't assume ID based shared libraries are being used.
-
This is the default.
-
--mmsshhaarreedd--lliibbrraarryy--iidd==nn
Specified the identification number of the ID based shared library being
-
compiled. Specifying a value of 0 will generate more compact code, specifying
other values will force the allocation of that number to the current
library but is no more space or time efficient than omitting this option.
_M_6_8_h_c_1_x _O_p_t_i_o_n_s
These are the --mm options defined for the 68hc11 and 68hc12
microcontrollers. The default values for these options depends on
which style of microcontroller was selected when the compiler was configured;
the defaults for the most common choices are given below.
-
--mm66881111
-
-
--mm6688hhcc1111
Generate output for a 68HC11. This is the default
-
when the compiler is configured for 68HC11-based systems.
-
--mm66881122
-
-
--mm6688hhcc1122
Generate output for a 68HC12. This is the default
-
when the compiler is configured for 68HC12-based systems.
-
--mm6688SS1122
-
-
--mm6688hhccss1122
Generate output for a 68HCS12.
-
-
--mmaauuttoo--iinnccddeecc
Enable the use of 68HC12 pre and post auto-increment and auto-decrement
-
addressing modes.
-
--mmiinnmmaaxx
-
-
--nnoommiinnmmaaxx
Enable the use of 68HC12 min and max instructions.
-
-
--mmlloonngg--ccaallllss
-
-
--mmnnoo--lloonngg--ccaallllss
Treat all calls as being far away (near). If calls are assumed to be
-
far away, the compiler will use the "call" instruction to
call a function and the "rtc" instruction for returning.
-
--mmsshhoorrtt
Consider type "int" to be 16 bits wide, like "short int".
-
-
--mmssoofftt--rreegg--ccoouunntt==_c_o_u_n_t
Specify the number of pseudo-soft registers which are used for the
-
code generation. The maximum number is 32. Using more pseudo-soft
register may or may not result in better code depending on the program.
The default is 4 for 68HC11 and 2 for 68HC12.
_M_C_o_r_e _O_p_t_i_o_n_s
These are the --mm options defined for the Motorola M*Core
processors.
-
--mmhhaarrddlliitt
-
-
--mmnnoo--hhaarrddlliitt
Inline constants into the code stream if it can be done in two
-
instructions or less.
-
--mmddiivv
-
-
--mmnnoo--ddiivv
Use the divide instruction. (Enabled by default).
-
-
--mmrreellaaxx--iimmmmeeddiiaattee
-
-
--mmnnoo--rreellaaxx--iimmmmeeddiiaattee
Allow arbitrary sized immediates in bit operations.
-
-
--mmwwiiddee--bbiittffiieellddss
-
-
--mmnnoo--wwiiddee--bbiittffiieellddss
Always treat bit-fields as int-sized.
-
-
--mm44bbyyttee--ffuunnccttiioonnss
-
-
--mmnnoo--44bbyyttee--ffuunnccttiioonnss
Force all functions to be aligned to a four byte boundary.
-
-
--mmccaallllggrraapphh--ddaattaa
-
-
--mmnnoo--ccaallllggrraapphh--ddaattaa
Emit callgraph information.
-
-
--mmssllooww--bbyytteess
-
-
--mmnnoo--ssllooww--bbyytteess
Prefer word access when reading byte quantities.
-
-
--mmlliittttllee--eennddiiaann
-
-
--mmbbiigg--eennddiiaann
Generate code for a little endian target.
-
-
--mm221100
-
-
--mm334400
Generate code for the 210 processor.
-
_M_I_P_S _O_p_t_i_o_n_s
-
--EEBB
Generate big-endian code.
-
-
--EELL
Generate little-endian code. This is the default for mmiippss**eell--**--**
-
configurations.
-
--mmaarrcchh==_a_r_c_h
Generate code that will run on _a_r_c_h, which can be the name of a
-
generic MIPS ISA, or the name of a particular processor.
The ISA names are:
mmiippss11, mmiippss22, mmiippss33, mmiippss44,
mmiippss3322, mmiippss3322rr22, and mmiippss6644.
The processor names are:
44kkcc, 44kkmm, 44kkpp,
55kkcc, 55kkff,
2200kkcc,
2244kk, 2244kkcc, 2244kkff, 2244kkxx,
mm44kk,
oorriioonn,
rr22000000, rr33000000, rr33990000, rr44000000, rr44440000,
rr44660000, rr44665500, rr66000000, rr88000000,
rrmm77000000, rrmm99000000,
ssbb11,
ssrr7711000000,
vvrr44110000, vvrr44111111, vvrr44112200, vvrr44113300, vvrr44330000,
vvrr55000000, vvrr55440000 and vvrr55550000.
The special value ffrroomm--aabbii selects the
most compatible architecture for the selected ABI (that is,
mmiippss11 for 32-bit ABIs and mmiippss33 for 64-bit ABIs).
In processor names, a final 000000 can be abbreviated as kk
(for example, --mmaarrcchh==rr22kk). Prefixes are optional, and
vvrr may be written rr.
GCC defines two macros based on the value of this option. The first
is __MMIIPPSS__AARRCCHH, which gives the name of target architecture, as
a string. The second has the form __MMIIPPSS__AARRCCHH___f_o_o,
where _f_o_o is the capitalized value of __MMIIPPSS__AARRCCHH.
For example, --mmaarrcchh==rr22000000 will set __MMIIPPSS__AARRCCHH
to ""rr22000000"" and define the macro __MMIIPPSS__AARRCCHH__RR22000000.
Note that the __MMIIPPSS__AARRCCHH macro uses the processor names given
above. In other words, it will have the full prefix and will not
abbreviate 000000 as kk. In the case of ffrroomm--aabbii,
the macro names the resolved architecture (either ""mmiippss11"" or
""mmiippss33""). It names the default architecture when no
--mmaarrcchh option is given.
-
--mmttuunnee==_a_r_c_h
Optimize for _a_r_c_h. Among other things, this option controls
-
the way instructions are scheduled, and the perceived cost of arithmetic
operations. The list of _a_r_c_h values is the same as for
--mmaarrcchh.
When this option is not used, GCC will optimize for the processor
specified by --mmaarrcchh. By using --mmaarrcchh and
--mmttuunnee together, it is possible to generate code that will
run on a family of processors, but optimize the code for one
particular member of that family.
--mmttuunnee defines the macros __MMIIPPSS__TTUUNNEE and
__MMIIPPSS__TTUUNNEE___f_o_o, which work in the same way as the
--mmaarrcchh ones described above.
-
--mmiippss11
Equivalent to --mmaarrcchh==mmiippss11.
-
-
--mmiippss22
Equivalent to --mmaarrcchh==mmiippss22.
-
-
--mmiippss33
Equivalent to --mmaarrcchh==mmiippss33.
-
-
--mmiippss44
Equivalent to --mmaarrcchh==mmiippss44.
-
-
--mmiippss3322
Equivalent to --mmaarrcchh==mmiippss3322.
-
-
--mmiippss3322rr22
Equivalent to --mmaarrcchh==mmiippss3322rr22.
-
-
--mmiippss6644
Equivalent to --mmaarrcchh==mmiippss6644.
-
-
--mmiippss1166
-
-
--mmnnoo--mmiippss1166
Generate (do not generate) MIPS16 code. If GCC is targetting a
-
MIPS32 or MIPS64 architecture, it will make use of the MIPS16e ASE.
-
--mmaabbii==3322
-
-
--mmaabbii==oo6644
-
-
--mmaabbii==nn3322
-
-
--mmaabbii==6644
-
-
--mmaabbii==eeaabbii
Generate code for the given ABI.
-
Note that the EABI has a 32-bit and a 64-bit variant. GCC normally
generates 64-bit code when you select a 64-bit architecture, but you
can use --mmggpp3322 to get 32-bit code instead.
For information about the O64 ABI, see
.
-
--mmaabbiiccaallllss
-
-
--mmnnoo--aabbiiccaallllss
Generate (do not generate) SVR4-style position-independent code.
-
--mmaabbiiccaallllss is the default for SVR4-based systems.
-
--mmxxggoott
-
-
--mmnnoo--xxggoott
Lift (do not lift) the usual restrictions on the size of the global
-
offset table.
GCC normally uses a single instruction to load values from the GOT.
While this is relatively efficient, it will only work if the GOT
is smaller than about 64k. Anything larger will cause the linker
to report an error such as:
relocation truncated to fit: R_MIPS_GOT16 foobar
If this happens, you should recompile your code with --mmxxggoott.
It should then work with very large GOTs, although it will also be
less efficient, since it will take three instructions to fetch the
value of a global symbol.
Note that some linkers can create multiple GOTs. If you have such a
linker, you should only need to use --mmxxggoott when a single object
file accesses more than 64k's worth of GOT entries. Very few do.
These options have no effect unless GCC is generating position
independent code.
-
--mmggpp3322
Assume that general-purpose registers are 32 bits wide.
-
-
--mmggpp6644
Assume that general-purpose registers are 64 bits wide.
-
-
--mmffpp3322
Assume that floating-point registers are 32 bits wide.
-
-
--mmffpp6644
Assume that floating-point registers are 64 bits wide.
-
-
--mmhhaarrdd--ffllooaatt
Use floating-point coprocessor instructions.
-
-
--mmssoofftt--ffllooaatt
Do not use floating-point coprocessor instructions. Implement
-
floating-point calculations using library calls instead.
-
--mmssiinnggllee--ffllooaatt
Assume that the floating-point coprocessor only supports single-precision
-
operations.
-
--mmddoouubbllee--ffllooaatt
Assume that the floating-point coprocessor supports double-precision
-
operations. This is the default.
-
--mmddsspp
-
-
--mmnnoo--ddsspp
Use (do not use) the MIPS DSP ASE.
-
-
--mmppaaiirreedd--ssiinnggllee
-
-
--mmnnoo--ppaaiirreedd--ssiinnggllee
Use (do not use) paired-single floating-point instructions.
-
This option can only be used
when generating 64-bit code and requires hardware floating-point
support to be enabled.
-
--mmiippss33dd
-
-
--mmnnoo--mmiippss33dd
Use (do not use) the MIPS-3D ASE.
-
The option --mmiippss33dd implies --mmppaaiirreedd--ssiinnggllee.
-
--mmlloonngg6644
Force "long" types to be 64 bits wide. See --mmlloonngg3322 for
-
an explanation of the default and the way that the pointer size is
determined.
-
--mmlloonngg3322
Force "long", "int", and pointer types to be 32 bits wide.
-
The default size of "int"s, "long"s and pointers depends on
the ABI. All the supported ABIs use 32-bit "int"s. The n64 ABI
uses 64-bit "long"s, as does the 64-bit EABI; the others use
32-bit "long"s. Pointers are the same size as "long"s,
or the same size as integer registers, whichever is smaller.
-
--mmssyymm3322
-
-
--mmnnoo--ssyymm3322
Assume (do not assume) that all symbols have 32-bit values, regardless
-
of the selected ABI. This option is useful in combination with
--mmaabbii==6644 and --mmnnoo--aabbiiccaallllss because it allows GCC
to generate shorter and faster references to symbolic addresses.
-
--GG _n_u_m
Put global and static items less than or equal to _n_u_m bytes into
-
the small data or bss section instead of the normal data or bss section.
This allows the data to be accessed using a single instruction.
All modules should be compiled with the same --GG _n_u_m
value.
-
--mmeemmbbeeddddeedd--ddaattaa
-
-
--mmnnoo--eemmbbeeddddeedd--ddaattaa
Allocate variables to the read-only data section first if possible, then
-
next in the small data section if possible, otherwise in data. This gives
slightly slower code than the default, but reduces the amount of RAM required
when executing, and thus may be preferred for some embedded systems.
-
--mmuunniinniitt--ccoonnsstt--iinn--rrooddaattaa
-
-
--mmnnoo--uunniinniitt--ccoonnsstt--iinn--rrooddaattaa
Put uninitialized "const" variables in the read-only data section.
-
This option is only meaningful in conjunction with --mmeemmbbeeddddeedd--ddaattaa.
-
--mmsspplliitt--aaddddrreesssseess
-
-
--mmnnoo--sspplliitt--aaddddrreesssseess
Enable (disable) use of the "%hi()" and "%lo()" assembler
-
relocation operators. This option has been superseded by
--mmeexxpplliicciitt--rreellooccss but is retained for backwards compatibility.
-
--mmeexxpplliicciitt--rreellooccss
-
-
--mmnnoo--eexxpplliicciitt--rreellooccss
Use (do not use) assembler relocation operators when dealing with symbolic
-
addresses. The alternative, selected by --mmnnoo--eexxpplliicciitt--rreellooccss,
is to use assembler macros instead.
--mmeexxpplliicciitt--rreellooccss is the default if GCC was configured
to use an assembler that supports relocation operators.
-
--mmcchheecckk--zzeerroo--ddiivviissiioonn
-
-
--mmnnoo--cchheecckk--zzeerroo--ddiivviissiioonn
Trap (do not trap) on integer division by zero. The default is
-
--mmcchheecckk--zzeerroo--ddiivviissiioonn.
-
--mmddiivviiddee--ttrraappss
-
-
--mmddiivviiddee--bbrreeaakkss
MIPS systems check for division by zero by generating either a
-
conditional trap or a break instruction. Using traps results in
smaller code, but is only supported on MIPS II and later. Also, some
versions of the Linux kernel have a bug that prevents trap from
generating the proper signal ("SIGFPE"). Use --mmddiivviiddee--ttrraappss to
allow conditional traps on architectures that support them and
--mmddiivviiddee--bbrreeaakkss to force the use of breaks.
The default is usually --mmddiivviiddee--ttrraappss, but this can be
overridden at configure time using ----wwiitthh--ddiivviiddee==bbrreeaakkss.
Divide-by-zero checks can be completely disabled using
--mmnnoo--cchheecckk--zzeerroo--ddiivviissiioonn.
-
--mmmmeemmccppyy
-
-
--mmnnoo--mmeemmccppyy
Force (do not force) the use of "memcpy()" for non-trivial block
-
moves. The default is --mmnnoo--mmeemmccppyy, which allows GCC to inline
most constant-sized copies.
-
--mmlloonngg--ccaallllss
-
-
--mmnnoo--lloonngg--ccaallllss
Disable (do not disable) use of the "jal" instruction. Calling
-
functions using "jal" is more efficient but requires the caller
and callee to be in the same 256 megabyte segment.
This option has no effect on abicalls code. The default is
--mmnnoo--lloonngg--ccaallllss.
-
--mmmmaadd
-
-
--mmnnoo--mmaadd
Enable (disable) use of the "mad", "madu" and "mul"
-
instructions, as provided by the R4650 ISA.
-
--mmffuusseedd--mmaadddd
-
-
--mmnnoo--ffuusseedd--mmaadddd
Enable (disable) use of the floating point multiply-accumulate
-
instructions, when they are available. The default is
--mmffuusseedd--mmaadddd.
When multiply-accumulate instructions are used, the intermediate
product is calculated to infinite precision and is not subject to
the FCSR Flush to Zero bit. This may be undesirable in some
circumstances.
-
--nnooccpppp
Tell the MIPS assembler to not run its preprocessor over user
-
assembler files (with a ..ss suffix) when assembling them.
-
--mmffiixx--rr44000000
-
-
--mmnnoo--ffiixx--rr44000000
Work around certain R4000 CPU errata:
-
-
-
A double-word or a variable shift may give an incorrect result if executed
-
immediately after starting an integer division.
-
-
A double-word or a variable shift may give an incorrect result if executed
-
while an integer multiplication is in progress.
-
-
An integer division may give an incorrect result if started in a delay slot
-
of a taken branch or a jump.
-
--mmffiixx--rr44440000
-
-
--mmnnoo--ffiixx--rr44440000
Work around certain R4400 CPU errata:
-
-
-
A double-word or a variable shift may give an incorrect result if executed
-
immediately after starting an integer division.
-
--mmffiixx--vvrr44112200
-
-
--mmnnoo--ffiixx--vvrr44112200
Work around certain VR4120 errata:
-
-
-
"dmultu" does not always produce the correct result.
-
-
-
"div" and "ddiv" do not always produce the correct result if one
-
of the operands is negative.
The workarounds for the division errata rely on special functions in
_l_i_b_g_c_c_._a. At present, these functions are only provided by
the "mips64vr*-elf" configurations.
Other VR4120 errata require a nop to be inserted between certain pairs of
instructions. These errata are handled by the assembler, not by GCC itself.
-
--mmffiixx--vvrr44113300
Work around the VR4130 "mflo"/"mfhi" errata. The
-
workarounds are implemented by the assembler rather than by GCC,
although GCC will avoid using "mflo" and "mfhi" if the
VR4130 "macc", "macchi", "dmacc" and "dmacchi"
instructions are available instead.
-
--mmffiixx--ssbb11
-
-
--mmnnoo--ffiixx--ssbb11
Work around certain SB-1 CPU core errata.
-
(This flag currently works around the SB-1 revision 2
"F1" and "F2" floating point errata.)
-
--mmfflluusshh--ffuunncc==_f_u_n_c
-
-
--mmnnoo--fflluusshh--ffuunncc
Specifies the function to call to flush the I and D caches, or to not
-
call any such function. If called, the function must take the same
arguments as the common "_flush_func()", that is, the address of the
memory range for which the cache is being flushed, the size of the
memory range, and the number 3 (to flush both caches). The default
depends on the target GCC was configured for, but commonly is either
__fflluusshh__ffuunncc or ____ccppuu__fflluusshh.
-
--mmbbrraanncchh--lliikkeellyy
-
-
--mmnnoo--bbrraanncchh--lliikkeellyy
Enable or disable use of Branch Likely instructions, regardless of the
-
default for the selected architecture. By default, Branch Likely
instructions may be generated if they are supported by the selected
architecture. An exception is for the MIPS32 and MIPS64 architectures
and processors which implement those architectures; for those, Branch
Likely instructions will not be generated by default because the MIPS32
and MIPS64 architectures specifically deprecate their use.
-
--mmffpp--eexxcceeppttiioonnss
-
-
--mmnnoo--ffpp--eexxcceeppttiioonnss
Specifies whether FP exceptions are enabled. This affects how we schedule
-
FP instructions for some processors. The default is that FP exceptions are
enabled.
For instance, on the SB-1, if FP exceptions are disabled, and we are emitting
64-bit code, then we can use both FP pipes. Otherwise, we can only use one
FP pipe.
-
--mmvvrr44113300--aalliiggnn
-
-
--mmnnoo--vvrr44113300--aalliiggnn
The VR4130 pipeline is two-way superscalar, but can only issue two
-
instructions together if the first one is 8-byte aligned. When this
option is enabled, GCC will align pairs of instructions that it
thinks should execute in parallel.
This option only has an effect when optimizing for the VR4130.
It normally makes code faster, but at the expense of making it bigger.
It is enabled by default at optimization level --OO33.
_M_M_I_X _O_p_t_i_o_n_s
These options are defined for the MMIX:
-
--mmlliibbffuunnccss
-
-
--mmnnoo--lliibbffuunnccss
Specify that intrinsic library functions are being compiled, passing all
-
values in registers, no matter the size.
-
--mmeeppssiilloonn
-
-
--mmnnoo--eeppssiilloonn
Generate floating-point comparison instructions that compare with respect
-
to the "rE" epsilon register.
-
--mmaabbii==mmmmiixxwwaarree
-
-
--mmaabbii==ggnnuu
Generate code that passes function parameters and return values that (in
-
the called function) are seen as registers $0 and up, as opposed to
the GNU ABI which uses global registers $231 and up.
-
--mmzzeerroo--eexxtteenndd
-
-
--mmnnoo--zzeerroo--eexxtteenndd
When reading data from memory in sizes shorter than 64 bits, use (do not
-
use) zero-extending load instructions by default, rather than
sign-extending ones.
-
--mmkknnuutthhddiivv
-
-
--mmnnoo--kknnuutthhddiivv
Make the result of a division yielding a remainder have the same sign as
-
the divisor. With the default, --mmnnoo--kknnuutthhddiivv, the sign of the
remainder follows the sign of the dividend. Both methods are
arithmetically valid, the latter being almost exclusively used.
-
--mmttoopplleevveell--ssyymmbboollss
-
-
--mmnnoo--ttoopplleevveell--ssyymmbboollss
Prepend (do not prepend) a :: to all global symbols, so the assembly
-
code can be used with the "PREFIX" assembly directive.
-
--mmeellff
Generate an executable in the ELF format, rather than the default
-
mmmmoo format used by the mmmmiixx simulator.
-
--mmbbrraanncchh--pprreeddiicctt
-
-
--mmnnoo--bbrraanncchh--pprreeddiicctt
Use (do not use) the probable-branch instructions, when static branch
-
prediction indicates a probable branch.
-
--mmbbaassee--aaddddrreesssseess
-
-
--mmnnoo--bbaassee--aaddddrreesssseess
Generate (do not generate) code that uses _b_a_s_e _a_d_d_r_e_s_s_e_s. Using a
-
base address automatically generates a request (handled by the assembler
and the linker) for a constant to be set up in a global register. The
register is used for one or more base address requests within the range 0
to 255 from the value held in the register. The generally leads to short
and fast code, but the number of different data items that can be
addressed is limited. This means that a program that uses lots of static
data may require --mmnnoo--bbaassee--aaddddrreesssseess.
-
--mmssiinnggllee--eexxiitt
-
-
--mmnnoo--ssiinnggllee--eexxiitt
Force (do not force) generated code to have a single exit point in each
-
function.
_M_N_1_0_3_0_0 _O_p_t_i_o_n_s
These --mm options are defined for Matsushita MN10300 architectures:
-
--mmmmuulltt--bbuugg
Generate code to avoid bugs in the multiply instructions for the MN10300
-
processors. This is the default.
-
--mmnnoo--mmuulltt--bbuugg
Do not generate code to avoid bugs in the multiply instructions for the
-
MN10300 processors.
-
--mmaamm3333
Generate code which uses features specific to the AM33 processor.
-
-
--mmnnoo--aamm3333
Do not generate code which uses features specific to the AM33 processor. This
-
is the default.
-
--mmrreettuurrnn--ppooiinntteerr--oonn--dd00
When generating a function which returns a pointer, return the pointer
-
in both "a0" and "d0". Otherwise, the pointer is returned
only in a0, and attempts to call such functions without a prototype
would result in errors. Note that this option is on by default; use
--mmnnoo--rreettuurrnn--ppooiinntteerr--oonn--dd00 to disable it.
-
--mmnnoo--ccrrtt00
Do not link in the C run-time initialization object file.
-
-
--mmrreellaaxx
Indicate to the linker that it should perform a relaxation optimization pass
-
to shorten branches, calls and absolute memory addresses. This option only
has an effect when used on the command line for the final link step.
This option makes symbolic debugging impossible.
_M_T _O_p_t_i_o_n_s
These --mm options are defined for Morpho MT architectures:
-
--mmaarrcchh==_c_p_u_-_t_y_p_e
Generate code that will run on _c_p_u_-_t_y_p_e, which is the name of a system
-
representing a certain processor type. Possible values for
_c_p_u_-_t_y_p_e are mmss11--6644--000011, mmss11--1166--000022,
mmss11--1166--000033 and mmss22.
When this option is not used, the default is --mmaarrcchh==mmss11--1166--000022.
-
--mmbbaacccc
Use byte loads and stores when generating code.
-
-
--mmnnoo--bbaacccc
Do not use byte loads and stores when generating code.
-
-
--mmssiimm
Use simulator runtime
-
-
--mmnnoo--ccrrtt00
Do not link in the C run-time initialization object file
-
_c_r_t_i_._o. Other run-time initialization and termination files
such as _s_t_a_r_t_u_p_._o and _e_x_i_t_._o are still included on the
linker command line.
_P_D_P_-_1_1 _O_p_t_i_o_n_s
These options are defined for the PDP-11:
-
--mmffppuu
Use hardware FPP floating point. This is the default. (FIS floating
-
point on the PDP-11/40 is not supported.)
-
--mmssoofftt--ffllooaatt
Do not use hardware floating point.
-
-
--mmaacc00
Return floating-point results in ac0 (fr0 in Unix assembler syntax).
-
-
--mmnnoo--aacc00
Return floating-point results in memory. This is the default.
-
-
--mm4400
Generate code for a PDP-11/40.
-
-
--mm4455
Generate code for a PDP-11/45. This is the default.
-
-
--mm1100
Generate code for a PDP-11/10.
-
-
--mmbbccooppyy--bbuuiillttiinn
Use inline "movmemhi" patterns for copying memory. This is the
-
default.
-
--mmbbccooppyy
Do not use inline "movmemhi" patterns for copying memory.
-
-
--mmiinntt1166
-
-
--mmnnoo--iinntt3322
Use 16-bit "int". This is the default.
-
-
--mmiinntt3322
-
-
--mmnnoo--iinntt1166
Use 32-bit "int".
-
-
--mmffllooaatt6644
-
-
--mmnnoo--ffllooaatt3322
Use 64-bit "float". This is the default.
-
-
--mmffllooaatt3322
-
-
--mmnnoo--ffllooaatt6644
Use 32-bit "float".
-
-
--mmaabbsshhii
Use "abshi2" pattern. This is the default.
-
-
--mmnnoo--aabbsshhii
Do not use "abshi2" pattern.
-
-
--mmbbrraanncchh--eexxppeennssiivvee
Pretend that branches are expensive. This is for experimenting with
-
code generation only.
-
--mmbbrraanncchh--cchheeaapp
Do not pretend that branches are expensive. This is the default.
-
-
--mmsspplliitt
Generate code for a system with split I&D.
-
-
--mmnnoo--sspplliitt
Generate code for a system without split I&D. This is the default.
-
-
--mmuunniixx--aassmm
Use Unix assembler syntax. This is the default when configured for
-
ppddpp1111--**--bbssdd.
-
--mmddeecc--aassmm
Use DEC assembler syntax. This is the default when configured for any
-
PDP-11 target other than ppddpp1111--**--bbssdd.
_P_o_w_e_r_P_C _O_p_t_i_o_n_s
These are listed under
_I_B_M _R_S_/_6_0_0_0 _a_n_d _P_o_w_e_r_P_C _O_p_t_i_o_n_s
These --mm options are defined for the IBM RS/6000 and PowerPC:
-
--mmppoowweerr
-
-
--mmnnoo--ppoowweerr
-
-
--mmppoowweerr22
-
-
--mmnnoo--ppoowweerr22
-
-
--mmppoowweerrppcc
-
-
--mmnnoo--ppoowweerrppcc
-
-
--mmppoowweerrppcc--ggppoopptt
-
-
--mmnnoo--ppoowweerrppcc--ggppoopptt
-
-
--mmppoowweerrppcc--ggffxxoopptt
-
-
--mmnnoo--ppoowweerrppcc--ggffxxoopptt
-
-
--mmppoowweerrppcc6644
-
-
--mmnnoo--ppoowweerrppcc6644
-
-
--mmmmffccrrff
-
-
--mmnnoo--mmffccrrff
-
-
--mmppooppccnnttbb
-
-
--mmnnoo--ppooppccnnttbb
-
-
--mmffpprrnndd
-
-
--mmnnoo--ffpprrnndd
GCC supports two related instruction set architectures for the
-
RS/6000 and PowerPC. The _P_O_W_E_R instruction set are those
instructions supported by the rriiooss chip set used in the original
RS/6000 systems and the _P_o_w_e_r_P_C instruction set is the
architecture of the Freescale MPC5xx, MPC6xx, MPC8xx microprocessors, and
the IBM 4xx, 6xx, and follow-on microprocessors.
Neither architecture is a subset of the other. However there is a
large common subset of instructions supported by both. An MQ
register is included in processors supporting the POWER architecture.
You use these options to specify which instructions are available on the
processor you are using. The default value of these options is
determined when configuring GCC. Specifying the
--mmccppuu==_c_p_u___t_y_p_e overrides the specification of these
options. We recommend you use the --mmccppuu==_c_p_u___t_y_p_e option
rather than the options listed above.
The --mmppoowweerr option allows GCC to generate instructions that
are found only in the POWER architecture and to use the MQ register.
Specifying --mmppoowweerr22 implies --ppoowweerr and also allows GCC
to generate instructions that are present in the POWER2 architecture but
not the original POWER architecture.
The --mmppoowweerrppcc option allows GCC to generate instructions that
are found only in the 32-bit subset of the PowerPC architecture.
Specifying --mmppoowweerrppcc--ggppoopptt implies --mmppoowweerrppcc and also allows
GCC to use the optional PowerPC architecture instructions in the
General Purpose group, including floating-point square root. Specifying
--mmppoowweerrppcc--ggffxxoopptt implies --mmppoowweerrppcc and also allows GCC to
use the optional PowerPC architecture instructions in the Graphics
group, including floating-point select.
The --mmmmffccrrff option allows GCC to generate the move from
condition register field instruction implemented on the POWER4
processor and other processors that support the PowerPC V2.01
architecture.
The --mmppooppccnnttbb option allows GCC to generate the popcount and
double precision FP reciprocal estimate instruction implemented on the
POWER5 processor and other processors that support the PowerPC V2.02
architecture.
The --mmffpprrnndd option allows GCC to generate the FP round to
integer instructions implemented on the POWER5+ processor and other
processors that support the PowerPC V2.03 architecture.
The --mmppoowweerrppcc6644 option allows GCC to generate the additional
64-bit instructions that are found in the full PowerPC64 architecture
and to treat GPRs as 64-bit, doubleword quantities. GCC defaults to
--mmnnoo--ppoowweerrppcc6644.
If you specify both --mmnnoo--ppoowweerr and --mmnnoo--ppoowweerrppcc, GCC
will use only the instructions in the common subset of both
architectures plus some special AIX common-mode calls, and will not use
the MQ register. Specifying both --mmppoowweerr and --mmppoowweerrppcc
permits GCC to use any instruction from either architecture and to
allow use of the MQ register; specify this for the Motorola MPC601.
-
--mmnneeww--mmnneemmoonniiccss
-
-
--mmoolldd--mmnneemmoonniiccss
Select which mnemonics to use in the generated assembler code. With
-
--mmnneeww--mmnneemmoonniiccss, GCC uses the assembler mnemonics defined for
the PowerPC architecture. With --mmoolldd--mmnneemmoonniiccss it uses the
assembler mnemonics defined for the POWER architecture. Instructions
defined in only one architecture have only one mnemonic; GCC uses that
mnemonic irrespective of which of these options is specified.
GCC defaults to the mnemonics appropriate for the architecture in
use. Specifying --mmccppuu==_c_p_u___t_y_p_e sometimes overrides the
value of these option. Unless you are building a cross-compiler, you
should normally not specify either --mmnneeww--mmnneemmoonniiccss or
--mmoolldd--mmnneemmoonniiccss, but should instead accept the default.
-
--mmccppuu==_c_p_u___t_y_p_e
Set architecture type, register usage, choice of mnemonics, and
-
instruction scheduling parameters for machine type _c_p_u___t_y_p_e.
Supported values for _c_p_u___t_y_p_e are 440011, 440033,
440055, 440055ffpp, 444400, 444400ffpp, 550055,
660011, 660022, 660033, 660033ee, 660044,
660044ee, 662200, 663300, 774400, 77440000,
77445500, 775500, 880011, 882211, 882233,
886600, 997700, 88554400, eecc660033ee, GG33,
GG44, GG55, ppoowweerr, ppoowweerr22, ppoowweerr33,
ppoowweerr44, ppoowweerr55, ppoowweerr55++,
ccoommmmoonn, ppoowweerrppcc, ppoowweerrppcc6644,
rriiooss, rriiooss11, rriiooss22, rrsscc, and rrss6644.
--mmccppuu==ccoommmmoonn selects a completely generic processor. Code
generated under this option will run on any POWER or PowerPC processor.
GCC will use only the instructions in the common subset of both
architectures, and will not use the MQ register. GCC assumes a generic
processor model for scheduling purposes.
--mmccppuu==ppoowweerr, --mmccppuu==ppoowweerr22, --mmccppuu==ppoowweerrppcc, and
--mmccppuu==ppoowweerrppcc6644 specify generic POWER, POWER2, pure 32-bit
PowerPC (i.e., not MPC601), and 64-bit PowerPC architecture machine
types, with an appropriate, generic processor model assumed for
scheduling purposes.
The other options specify a specific processor. Code generated under
those options will run best on that processor, and may not run at all on
others.
The --mmccppuu options automatically enable or disable the
following options: --mmaallttiivveecc, --mmffpprrnndd,
--mmhhaarrdd--ffllooaatt, --mmmmffccrrff, --mmmmuullttiippllee,
--mmnneeww--mmnneemmoonniiccss, --mmppooppccnnttbb, --mmppoowweerr,
--mmppoowweerr22, --mmppoowweerrppcc6644, --mmppoowweerrppcc--ggppoopptt,
--mmppoowweerrppcc--ggffxxoopptt, --mmssttrriinngg. The particular options
set for any particular CPU will vary between compiler versions,
depending on what setting seems to produce optimal code for that CPU;
it doesn't necessarily reflect the actual hardware's capabilities. If
you wish to set an individual option to a particular value, you may
specify it after the --mmccppuu option, like --mmccppuu==997700
--mmnnoo--aallttiivveecc.
On AIX, the --mmaallttiivveecc and --mmppoowweerrppcc6644 options are
not enabled or disabled by the --mmccppuu option at present because
AIX does not have full support for these options. You may still
enable or disable them individually if you're sure it'll work in your
environment.
-
--mmttuunnee==_c_p_u___t_y_p_e
Set the instruction scheduling parameters for machine type
-
_c_p_u___t_y_p_e, but do not set the architecture type, register usage, or
choice of mnemonics, as --mmccppuu==_c_p_u___t_y_p_e would. The same
values for _c_p_u___t_y_p_e are used for --mmttuunnee as for
--mmccppuu. If both are specified, the code generated will use the
architecture, registers, and mnemonics set by --mmccppuu, but the
scheduling parameters set by --mmttuunnee.
-
--mmsswwddiivv
-
-
--mmnnoo--sswwddiivv
Generate code to compute division as reciprocal estimate and iterative
-
refinement, creating opportunities for increased throughput. This
feature requires: optional PowerPC Graphics instruction set for single
precision and FRE instruction for double precision, assuming divides
cannot generate user-visible traps, and the domain values not include
Infinities, denormals or zero denominator.
-
--mmaallttiivveecc
-
-
--mmnnoo--aallttiivveecc
Generate code that uses (does not use) AltiVec instructions, and also
-
enable the use of built-in functions that allow more direct access to
the AltiVec instruction set. You may also need to set
--mmaabbii==aallttiivveecc to adjust the current ABI with AltiVec ABI
enhancements.
-
--mmvvrrssaavvee
-
-
--mmnnoo--vvrrssaavvee
Generate VRSAVE instructions when generating AltiVec code.
-
-
--mmsseeccuurree--pplltt
Generate code that allows ld and ld.so to build executables and shared
-
libraries with non-exec .plt and .got sections. This is a PowerPC
32-bit SYSV ABI option.
-
--mmbbssss--pplltt
Generate code that uses a BSS .plt section that ld.so fills in, and
-
requires .plt and .got sections that are both writable and executable.
This is a PowerPC 32-bit SYSV ABI option.
-
--mmiisseell
-
-
--mmnnoo--iisseell
This switch enables or disables the generation of ISEL instructions.
-
-
--mmiisseell==_y_e_s_/_n_o
This switch has been deprecated. Use --mmiisseell and
-
--mmnnoo--iisseell instead.
-
--mmssppee
-
-
--mmnnoo--iisseell
This switch enables or disables the generation of SPE simd
-
instructions.
-
--mmssppee==_y_e_s_/_n_o
This option has been deprecated. Use --mmssppee and
-
--mmnnoo--ssppee instead.
-
--mmffllooaatt--ggpprrss==_y_e_s_/_s_i_n_g_l_e_/_d_o_u_b_l_e_/_n_o
-
-
--mmffllooaatt--ggpprrss
This switch enables or disables the generation of floating point
-
operations on the general purpose registers for architectures that
support it.
The argument _y_e_s or _s_i_n_g_l_e enables the use of
single-precision floating point operations.
The argument _d_o_u_b_l_e enables the use of single and
double-precision floating point operations.
The argument _n_o disables floating point operations on the
general purpose registers.
This option is currently only available on the MPC854x.
-
--mm3322
-
-
--mm6644
Generate code for 32-bit or 64-bit environments of Darwin and SVR4
-
targets (including GNU/Linux). The 32-bit environment sets int, long
and pointer to 32 bits and generates code that runs on any PowerPC
variant. The 64-bit environment sets int to 32 bits and long and
pointer to 64 bits, and generates code for PowerPC64, as for
--mmppoowweerrppcc6644.
-
--mmffuullll--ttoocc
-
-
--mmnnoo--ffpp--iinn--ttoocc
-
-
--mmnnoo--ssuumm--iinn--ttoocc
-
-
--mmmmiinniimmaall--ttoocc
Modify generation of the TOC (Table Of Contents), which is created for
-
every executable file. The --mmffuullll--ttoocc option is selected by
default. In that case, GCC will allocate at least one TOC entry for
each unique non-automatic variable reference in your program. GCC
will also place floating-point constants in the TOC. However, only
16,384 entries are available in the TOC.
If you receive a linker error message that saying you have overflowed
the available TOC space, you can reduce the amount of TOC space used
with the --mmnnoo--ffpp--iinn--ttoocc and --mmnnoo--ssuumm--iinn--ttoocc options.
--mmnnoo--ffpp--iinn--ttoocc prevents GCC from putting floating-point
constants in the TOC and --mmnnoo--ssuumm--iinn--ttoocc forces GCC to
generate code to calculate the sum of an address and a constant at
run-time instead of putting that sum into the TOC. You may specify one
or both of these options. Each causes GCC to produce very slightly
slower and larger code at the expense of conserving TOC space.
If you still run out of space in the TOC even when you specify both of
these options, specify --mmmmiinniimmaall--ttoocc instead. This option causes
GCC to make only one TOC entry for every file. When you specify this
option, GCC will produce code that is slower and larger but which
uses extremely little TOC space. You may wish to use this option
only on files that contain less frequently executed code.
-
--mmaaiixx6644
-
-
--mmaaiixx3322
Enable 64-bit AIX ABI and calling convention: 64-bit pointers, 64-bit
-
"long" type, and the infrastructure needed to support them.
Specifying --mmaaiixx6644 implies --mmppoowweerrppcc6644 and
--mmppoowweerrppcc, while --mmaaiixx3322 disables the 64-bit ABI and
implies --mmnnoo--ppoowweerrppcc6644. GCC defaults to --mmaaiixx3322.
-
--mmxxll--ccoommppaatt
-
-
--mmnnoo--xxll--ccoommppaatt
Produce code that conforms more closely to IBM XL compiler semantics
-
when using AIX-compatible ABI. Pass floating-point arguments to
prototyped functions beyond the register save area (RSA) on the stack
in addition to argument FPRs. Do not assume that most significant
double in 128-bit long double value is properly rounded when comparing
values and converting to double. Use XL symbol names for long double
support routines.
The AIX calling convention was extended but not initially documented to
handle an obscure K&R C case of calling a function that takes the
address of its arguments with fewer arguments than declared. IBM XL
compilers access floating point arguments which do not fit in the
RSA from the stack when a subroutine is compiled without
optimization. Because always storing floating-point arguments on the
stack is inefficient and rarely needed, this option is not enabled by
default and only is necessary when calling subroutines compiled by IBM
XL compilers without optimization.
-
--mmppee
Support _I_B_M _R_S_/_6_0_0_0 _S_P _P_a_r_a_l_l_e_l _E_n_v_i_r_o_n_m_e_n_t (PE). Link an
-
application written to use message passing with special startup code to
enable the application to run. The system must have PE installed in the
standard location (_/_u_s_r_/_l_p_p_/_p_p_e_._p_o_e_/), or the _s_p_e_c_s file
must be overridden with the --ssppeeccss== option to specify the
appropriate directory location. The Parallel Environment does not
support threads, so the --mmppee option and the --pptthhrreeaadd
option are incompatible.
-
--mmaalliiggnn--nnaattuurraall
-
-
--mmaalliiggnn--ppoowweerr
On AIX, 32-bit Darwin, and 64-bit PowerPC GNU/Linux, the option
-
--mmaalliiggnn--nnaattuurraall overrides the ABI-defined alignment of larger
types, such as floating-point doubles, on their natural size-based boundary.
The option --mmaalliiggnn--ppoowweerr instructs GCC to follow the ABI-specified
alignment rules. GCC defaults to the standard alignment defined in the ABI.
On 64-bit Darwin, natural alignment is the default, and --mmaalliiggnn--ppoowweerr
is not supported.
-
--mmssoofftt--ffllooaatt
-
-
--mmhhaarrdd--ffllooaatt
Generate code that does not use (uses) the floating-point register set.
-
Software floating point emulation is provided if you use the
--mmssoofftt--ffllooaatt option, and pass the option to GCC when linking.
-
--mmmmuullttiippllee
-
-
--mmnnoo--mmuullttiippllee
Generate code that uses (does not use) the load multiple word
-
instructions and the store multiple word instructions. These
instructions are generated by default on POWER systems, and not
generated on PowerPC systems. Do not use --mmmmuullttiippllee on little
endian PowerPC systems, since those instructions do not work when the
processor is in little endian mode. The exceptions are PPC740 and
PPC750 which permit the instructions usage in little endian mode.
-
--mmssttrriinngg
-
-
--mmnnoo--ssttrriinngg
Generate code that uses (does not use) the load string instructions
-
and the store string word instructions to save multiple registers and
do small block moves. These instructions are generated by default on
POWER systems, and not generated on PowerPC systems. Do not use
--mmssttrriinngg on little endian PowerPC systems, since those
instructions do not work when the processor is in little endian mode.
The exceptions are PPC740 and PPC750 which permit the instructions
usage in little endian mode.
-
--mmuuppddaattee
-
-
--mmnnoo--uuppddaattee
Generate code that uses (does not use) the load or store instructions
-
that update the base register to the address of the calculated memory
location. These instructions are generated by default. If you use
--mmnnoo--uuppddaattee, there is a small window between the time that the
stack pointer is updated and the address of the previous frame is
stored, which means code that walks the stack frame across interrupts or
signals may get corrupted data.
-
--mmffuusseedd--mmaadddd
-
-
--mmnnoo--ffuusseedd--mmaadddd
Generate code that uses (does not use) the floating point multiply and
-
accumulate instructions. These instructions are generated by default if
hardware floating is used.
-
--mmnnoo--bbiitt--aalliiggnn
-
-
--mmbbiitt--aalliiggnn
On System V.4 and embedded PowerPC systems do not (do) force structures
-
and unions that contain bit-fields to be aligned to the base type of the
bit-field.
For example, by default a structure containing nothing but 8
"unsigned" bit-fields of length 1 would be aligned to a 4 byte
boundary and have a size of 4 bytes. By using --mmnnoo--bbiitt--aalliiggnn,
the structure would be aligned to a 1 byte boundary and be one byte in
size.
-
--mmnnoo--ssttrriicctt--aalliiggnn
-
-
--mmssttrriicctt--aalliiggnn
On System V.4 and embedded PowerPC systems do not (do) assume that
-
unaligned memory references will be handled by the system.
-
--mmrreellooccaattaabbllee
-
-
--mmnnoo--rreellooccaattaabbllee
On embedded PowerPC systems generate code that allows (does not allow)
-
the program to be relocated to a different address at runtime. If you
use --mmrreellooccaattaabbllee on any module, all objects linked together must
be compiled with --mmrreellooccaattaabbllee or --mmrreellooccaattaabbllee--lliibb.
-
--mmrreellooccaattaabbllee--lliibb
-
-
--mmnnoo--rreellooccaattaabbllee--lliibb
On embedded PowerPC systems generate code that allows (does not allow)
-
the program to be relocated to a different address at runtime. Modules
compiled with --mmrreellooccaattaabbllee--lliibb can be linked with either modules
compiled without --mmrreellooccaattaabbllee and --mmrreellooccaattaabbllee--lliibb or
with modules compiled with the --mmrreellooccaattaabbllee options.
-
--mmnnoo--ttoocc
-
-
--mmttoocc
On System V.4 and embedded PowerPC systems do not (do) assume that
-
register 2 contains a pointer to a global area pointing to the addresses
used in the program.
-
--mmlliittttllee
-
-
--mmlliittttllee--eennddiiaann
On System V.4 and embedded PowerPC systems compile code for the
-
processor in little endian mode. The --mmlliittttllee--eennddiiaann option is
the same as --mmlliittttllee.
-
--mmbbiigg
-
-
--mmbbiigg--eennddiiaann
On System V.4 and embedded PowerPC systems compile code for the
-
processor in big endian mode. The --mmbbiigg--eennddiiaann option is
the same as --mmbbiigg.
-
--mmddyynnaammiicc--nnoo--ppiicc
On Darwin and Mac OS X systems, compile code so that it is not
-
relocatable, but that its external references are relocatable. The
resulting code is suitable for applications, but not shared
libraries.
-
--mmpprriioorriittiizzee--rreessttrriicctteedd--iinnssnnss==_p_r_i_o_r_i_t_y
This option controls the priority that is assigned to
-
dispatch-slot restricted instructions during the second scheduling
pass. The argument _p_r_i_o_r_i_t_y takes the value _0_/_1_/_2 to assign
_n_o_/_h_i_g_h_e_s_t_/_s_e_c_o_n_d_-_h_i_g_h_e_s_t priority to dispatch slot restricted
instructions.
-
--mmsscchheedd--ccoossttllyy--ddeepp==_d_e_p_e_n_d_e_n_c_e___t_y_p_e
This option controls which dependences are considered costly
-
by the target during instruction scheduling. The argument
_d_e_p_e_n_d_e_n_c_e___t_y_p_e takes one of the following values:
_n_o: no dependence is costly,
_a_l_l: all dependences are costly,
_t_r_u_e___s_t_o_r_e___t_o___l_o_a_d: a true dependence from store to load is costly,
_s_t_o_r_e___t_o___l_o_a_d: any dependence from store to load is costly,
_n_u_m_b_e_r: any dependence which latency >= _n_u_m_b_e_r is costly.
-
--mmiinnsseerrtt--sscchheedd--nnooppss==_s_c_h_e_m_e
This option controls which nop insertion scheme will be used during
-
the second scheduling pass. The argument _s_c_h_e_m_e takes one of the
following values:
_n_o: Don't insert nops.
_p_a_d: Pad with nops any dispatch group which has vacant issue slots,
according to the scheduler's grouping.
_r_e_g_r_o_u_p___e_x_a_c_t: Insert nops to force costly dependent insns into
separate groups. Insert exactly as many nops as needed to force an insn
to a new group, according to the estimated processor grouping.
_n_u_m_b_e_r: Insert nops to force costly dependent insns into
separate groups. Insert _n_u_m_b_e_r nops to force an insn to a new group.
-
--mmccaallll--ssyyssvv
On System V.4 and embedded PowerPC systems compile code using calling
-
conventions that adheres to the March 1995 draft of the System V
Application Binary Interface, PowerPC processor supplement. This is the
default unless you configured GCC using ppoowweerrppcc--**--eeaabbiiaaiixx.
-
--mmccaallll--ssyyssvv--eeaabbii
Specify both --mmccaallll--ssyyssvv and --mmeeaabbii options.
-
-
--mmccaallll--ssyyssvv--nnooeeaabbii
Specify both --mmccaallll--ssyyssvv and --mmnnoo--eeaabbii options.
-
-
--mmccaallll--ssoollaarriiss
On System V.4 and embedded PowerPC systems compile code for the Solaris
-
operating system.
-
--mmccaallll--lliinnuuxx
On System V.4 and embedded PowerPC systems compile code for the
-
Linux-based GNU system.
-
--mmccaallll--ggnnuu
On System V.4 and embedded PowerPC systems compile code for the
-
Hurd-based GNU system.
-
--mmccaallll--nneettbbssdd
On System V.4 and embedded PowerPC systems compile code for the
-
NetBSD operating system.
-
--mmaaiixx--ssttrruucctt--rreettuurrnn
Return all structures in memory (as specified by the AIX ABI).
-
-
--mmssvvrr44--ssttrruucctt--rreettuurrnn
Return structures smaller than 8 bytes in registers (as specified by the
-
SVR4 ABI).
-
--mmaabbii==_a_b_i_-_t_y_p_e
Extend the current ABI with a particular extension, or remove such extension.
-
Valid values are _a_l_t_i_v_e_c, _n_o_-_a_l_t_i_v_e_c, _s_p_e,
_n_o_-_s_p_e, _i_b_m_l_o_n_g_d_o_u_b_l_e, _i_e_e_e_l_o_n_g_d_o_u_b_l_e.
-
--mmaabbii==ssppee
Extend the current ABI with SPE ABI extensions. This does not change
-
the default ABI, instead it adds the SPE ABI extensions to the current
ABI.
-
--mmaabbii==nnoo--ssppee
Disable Booke SPE ABI extensions for the current ABI.
-
-
--mmaabbii==iibbmmlloonnggddoouubbllee
Change the current ABI to use IBM extended precision long double.
-
This is a PowerPC 32-bit SYSV ABI option.
-
--mmaabbii==iieeeeeelloonnggddoouubbllee
Change the current ABI to use IEEE extended precision long double.
-
This is a PowerPC 32-bit Linux ABI option.
-
--mmpprroottoottyyppee
-
-
--mmnnoo--pprroottoottyyppee
On System V.4 and embedded PowerPC systems assume that all calls to
-
variable argument functions are properly prototyped. Otherwise, the
compiler must insert an instruction before every non prototyped call to
set or clear bit 6 of the condition code register (_C_R) to
indicate whether floating point values were passed in the floating point
registers in case the function takes a variable arguments. With
--mmpprroottoottyyppee, only calls to prototyped variable argument functions
will set or clear the bit.
-
--mmssiimm
On embedded PowerPC systems, assume that the startup module is called
-
_s_i_m_-_c_r_t_0_._o and that the standard C libraries are _l_i_b_s_i_m_._a and
_l_i_b_c_._a. This is the default for ppoowweerrppcc--**--eeaabbiissiimm.
configurations.
-
--mmmmvvmmee
On embedded PowerPC systems, assume that the startup module is called
-
_c_r_t_0_._o and the standard C libraries are _l_i_b_m_v_m_e_._a and
_l_i_b_c_._a.
-
--mmaaddss
On embedded PowerPC systems, assume that the startup module is called
-
_c_r_t_0_._o and the standard C libraries are _l_i_b_a_d_s_._a and
_l_i_b_c_._a.
-
--mmyyeelllloowwkknniiffee
On embedded PowerPC systems, assume that the startup module is called
-
_c_r_t_0_._o and the standard C libraries are _l_i_b_y_k_._a and
_l_i_b_c_._a.
-
--mmvvxxwwoorrkkss
On System V.4 and embedded PowerPC systems, specify that you are
-
compiling for a VxWorks system.
-
--mmwwiinnddiissss
Specify that you are compiling for the WindISS simulation environment.
-
-
--mmeemmbb
On embedded PowerPC systems, set the _P_P_C___E_M_B bit in the ELF flags
-
header to indicate that eeaabbii extended relocations are used.
-
--mmeeaabbii
-
-
--mmnnoo--eeaabbii
On System V.4 and embedded PowerPC systems do (do not) adhere to the
-
Embedded Applications Binary Interface (eabi) which is a set of
modifications to the System V.4 specifications. Selecting --mmeeaabbii
means that the stack is aligned to an 8 byte boundary, a function
"__eabi" is called to from "main" to set up the eabi
environment, and the --mmssddaattaa option can use both "r2" and
"r13" to point to two separate small data areas. Selecting
--mmnnoo--eeaabbii means that the stack is aligned to a 16 byte boundary,
do not call an initialization function from "main", and the
--mmssddaattaa option will only use "r13" to point to a single
small data area. The --mmeeaabbii option is on by default if you
configured GCC using one of the ppoowweerrppcc**--**--eeaabbii** options.
-
--mmssddaattaa==eeaabbii
On System V.4 and embedded PowerPC systems, put small initialized
-
"const" global and static data in the ..ssddaattaa22 section, which
is pointed to by register "r2". Put small initialized
non-"const" global and static data in the ..ssddaattaa section,
which is pointed to by register "r13". Put small uninitialized
global and static data in the ..ssbbssss section, which is adjacent to
the ..ssddaattaa section. The --mmssddaattaa==eeaabbii option is
incompatible with the --mmrreellooccaattaabbllee option. The
--mmssddaattaa==eeaabbii option also sets the --mmeemmbb option.
-
--mmssddaattaa==ssyyssvv
On System V.4 and embedded PowerPC systems, put small global and static
-
data in the ..ssddaattaa section, which is pointed to by register
"r13". Put small uninitialized global and static data in the
..ssbbssss section, which is adjacent to the ..ssddaattaa section.
The --mmssddaattaa==ssyyssvv option is incompatible with the
--mmrreellooccaattaabbllee option.
-
--mmssddaattaa==ddeeffaauulltt
-
-
--mmssddaattaa
On System V.4 and embedded PowerPC systems, if --mmeeaabbii is used,
-
compile code the same as --mmssddaattaa==eeaabbii, otherwise compile code the
same as --mmssddaattaa==ssyyssvv.
-
--mmssddaattaa--ddaattaa
On System V.4 and embedded PowerPC systems, put small global and static
-
data in the ..ssddaattaa section. Put small uninitialized global and
static data in the ..ssbbssss section. Do not use register "r13"
to address small data however. This is the default behavior unless
other --mmssddaattaa options are used.
-
--mmssddaattaa==nnoonnee
-
-
--mmnnoo--ssddaattaa
On embedded PowerPC systems, put all initialized global and static data
-
in the ..ddaattaa section, and all uninitialized data in the
..bbssss section.
-
--GG _n_u_m
On embedded PowerPC systems, put global and static items less than or
-
equal to _n_u_m bytes into the small data or bss sections instead of
the normal data or bss section. By default, _n_u_m is 8. The
--GG _n_u_m switch is also passed to the linker.
All modules should be compiled with the same --GG _n_u_m value.
-
--mmrreeggnnaammeess
-
-
--mmnnoo--rreeggnnaammeess
On System V.4 and embedded PowerPC systems do (do not) emit register
-
names in the assembly language output using symbolic forms.
-
--mmlloonnggccaallll
-
-
--mmnnoo--lloonnggccaallll
Default to making all function calls indirectly, using a register, so
-
that functions which reside further than 32 megabytes (33,554,432
bytes) from the current location can be called. This setting can be
overridden by the "shortcall" function attribute, or by
"#pragma longcall(0)".
Some linkers are capable of detecting out-of-range calls and generating
glue code on the fly. On these systems, long calls are unnecessary and
generate slower code. As of this writing, the AIX linker can do this,
as can the GNU linker for PowerPC/64. It is planned to add this feature
to the GNU linker for 32-bit PowerPC systems as well.
On Darwin/PPC systems, "#pragma longcall" will generate "jbsr
callee, L42", plus a "branch island" (glue code). The two target
addresses represent the callee and the "branch island". The
Darwin/PPC linker will prefer the first address and generate a "bl
callee" if the PPC "bl" instruction will reach the callee directly;
otherwise, the linker will generate "bl L42" to call the "branch
island". The "branch island" is appended to the body of the
calling function; it computes the full 32-bit address of the callee
and jumps to it.
On Mach-O (Darwin) systems, this option directs the compiler emit to
the glue for every direct call, and the Darwin linker decides whether
to use or discard it.
In the future, we may cause GCC to ignore all longcall specifications
when the linker is known to generate glue.
-
--pptthhrreeaadd
Adds support for multithreading with the _p_t_h_r_e_a_d_s library.
-
This option sets flags for both the preprocessor and linker.
_S_/_3_9_0 _a_n_d _z_S_e_r_i_e_s _O_p_t_i_o_n_s
These are the --mm options defined for the S/390 and zSeries architecture.
-
--mmhhaarrdd--ffllooaatt
-
-
--mmssoofftt--ffllooaatt
Use (do not use) the hardware floating-point instructions and registers
-
for floating-point operations. When --mmssoofftt--ffllooaatt is specified,
functions in _l_i_b_g_c_c_._a will be used to perform floating-point
operations. When --mmhhaarrdd--ffllooaatt is specified, the compiler
generates IEEE floating-point instructions. This is the default.
-
--mmlloonngg--ddoouubbllee--6644
-
-
--mmlloonngg--ddoouubbllee--112288
These switches control the size of "long double" type. A size
-
of 64bit makes the "long double" type equivalent to the "double"
type. This is the default.
-
--mmbbaacckkcchhaaiinn
-
-
--mmnnoo--bbaacckkcchhaaiinn
Store (do not store) the address of the caller's frame as backchain pointer
-
into the callee's stack frame.
A backchain may be needed to allow debugging using tools that do not understand
DWARF-2 call frame information.
When --mmnnoo--ppaacckkeedd--ssttaacckk is in effect, the backchain pointer is stored
at the bottom of the stack frame; when --mmppaacckkeedd--ssttaacckk is in effect,
the backchain is placed into the topmost word of the 96/160 byte register
save area.
In general, code compiled with --mmbbaacckkcchhaaiinn is call-compatible with
code compiled with --mmmmoo--bbaacckkcchhaaiinn; however, use of the backchain
for debugging purposes usually requires that the whole binary is built with
--mmbbaacckkcchhaaiinn. Note that the combination of --mmbbaacckkcchhaaiinn,
--mmppaacckkeedd--ssttaacckk and --mmhhaarrdd--ffllooaatt is not supported. In order
to build a linux kernel use --mmssoofftt--ffllooaatt.
The default is to not maintain the backchain.
-
--mmppaacckkeedd--ssttaacckk
-
-
--mmnnoo--ppaacckkeedd--ssttaacckk
Use (do not use) the packed stack layout. When --mmnnoo--ppaacckkeedd--ssttaacckk is
-
specified, the compiler uses the all fields of the 96/160 byte register save
area only for their default purpose; unused fields still take up stack space.
When --mmppaacckkeedd--ssttaacckk is specified, register save slots are densely
packed at the top of the register save area; unused space is reused for other
purposes, allowing for more efficient use of the available stack space.
However, when --mmbbaacckkcchhaaiinn is also in effect, the topmost word of
the save area is always used to store the backchain, and the return address
register is always saved two words below the backchain.
As long as the stack frame backchain is not used, code generated with
--mmppaacckkeedd--ssttaacckk is call-compatible with code generated with
--mmnnoo--ppaacckkeedd--ssttaacckk. Note that some non-FSF releases of GCC 2.95 for
S/390 or zSeries generated code that uses the stack frame backchain at run
time, not just for debugging purposes. Such code is not call-compatible
with code compiled with --mmppaacckkeedd--ssttaacckk. Also, note that the
combination of --mmbbaacckkcchhaaiinn,
--mmppaacckkeedd--ssttaacckk and --mmhhaarrdd--ffllooaatt is not supported. In order
to build a linux kernel use --mmssoofftt--ffllooaatt.
The default is to not use the packed stack layout.
-
--mmssmmaallll--eexxeecc
-
-
--mmnnoo--ssmmaallll--eexxeecc
Generate (or do not generate) code using the "bras" instruction
-
to do subroutine calls.
This only works reliably if the total executable size does not
exceed 64k. The default is to use the "basr" instruction instead,
which does not have this limitation.
-
--mm6644
-
-
--mm3311
When --mm3311 is specified, generate code compliant to the
-
GNU/Linux for S/390 ABI. When --mm6644 is specified, generate
code compliant to the GNU/Linux for zSeries ABI. This allows GCC in
particular to generate 64-bit instructions. For the ss339900
targets, the default is --mm3311, while the ss339900xx
targets default to --mm6644.
-
--mmzzaarrcchh
-
-
--mmeessaa
When --mmzzaarrcchh is specified, generate code using the
-
instructions available on z/Architecture.
When --mmeessaa is specified, generate code using the
instructions available on ESA/390. Note that --mmeessaa is
not possible with --mm6644.
When generating code compliant to the GNU/Linux for S/390 ABI,
the default is --mmeessaa. When generating code compliant
to the GNU/Linux for zSeries ABI, the default is --mmzzaarrcchh.
-
--mmmmvvccllee
-
-
--mmnnoo--mmvvccllee
Generate (or do not generate) code using the "mvcle" instruction
-
to perform block moves. When --mmnnoo--mmvvccllee is specified,
use a "mvc" loop instead. This is the default unless optimizing for
size.
-
--mmddeebbuugg
-
-
--mmnnoo--ddeebbuugg
Print (or do not print) additional debug information when compiling.
-
The default is to not print debug information.
-
--mmaarrcchh==_c_p_u_-_t_y_p_e
Generate code that will run on _c_p_u_-_t_y_p_e, which is the name of a system
-
representing a certain processor type. Possible values for
_c_p_u_-_t_y_p_e are gg55, gg66, zz990000, and zz999900.
When generating code using the instructions available on z/Architecture,
the default is --mmaarrcchh==zz990000. Otherwise, the default is
--mmaarrcchh==gg55.
-
--mmttuunnee==_c_p_u_-_t_y_p_e
Tune to _c_p_u_-_t_y_p_e everything applicable about the generated code,
-
except for the ABI and the set of available instructions.
The list of _c_p_u_-_t_y_p_e values is the same as for --mmaarrcchh.
The default is the value used for --mmaarrcchh.
-
--mmttppff--ttrraaccee
-
-
--mmnnoo--ttppff--ttrraaccee
Generate code that adds (does not add) in TPF OS specific branches to trace
-
routines in the operating system. This option is off by default, even
when compiling for the TPF OS.
-
--mmffuusseedd--mmaadddd
-
-
--mmnnoo--ffuusseedd--mmaadddd
Generate code that uses (does not use) the floating point multiply and
-
accumulate instructions. These instructions are generated by default if
hardware floating point is used.
-
--mmwwaarrnn--ffrraammeessiizzee==_f_r_a_m_e_s_i_z_e
Emit a warning if the current function exceeds the given frame size. Because
-
this is a compile time check it doesn't need to be a real problem when the program
runs. It is intended to identify functions which most probably cause
a stack overflow. It is useful to be used in an environment with limited stack
size e.g. the linux kernel.
-
--mmwwaarrnn--ddyynnaammiiccssttaacckk
Emit a warning if the function calls alloca or uses dynamically
-
sized arrays. This is generally a bad idea with a limited stack size.
-
--mmssttaacckk--gguuaarrdd==_s_t_a_c_k_-_g_u_a_r_d
-
-
--mmssttaacckk--ssiizzee==_s_t_a_c_k_-_s_i_z_e
These arguments always have to be used in conjunction. If they are present the s390
-
back end emits additional instructions in the function prologue which trigger a trap
if the stack size is _s_t_a_c_k_-_g_u_a_r_d bytes above the _s_t_a_c_k_-_s_i_z_e
(remember that the stack on s390 grows downward). These options are intended to
be used to help debugging stack overflow problems. The additionally emitted code
causes only little overhead and hence can also be used in production like systems
without greater performance degradation. The given values have to be exact
powers of 2 and _s_t_a_c_k_-_s_i_z_e has to be greater than _s_t_a_c_k_-_g_u_a_r_d without
exceeding 64k.
In order to be efficient the extra code makes the assumption that the stack starts
at an address aligned to the value given by _s_t_a_c_k_-_s_i_z_e.
_S_H _O_p_t_i_o_n_s
These --mm options are defined for the SH implementations:
-
--mm11
Generate code for the SH1.
-
-
--mm22
Generate code for the SH2.
-
-
--mm22ee
Generate code for the SH2e.
-
-
--mm33
Generate code for the SH3.
-
-
--mm33ee
Generate code for the SH3e.
-
-
--mm44--nnooffppuu
Generate code for the SH4 without a floating-point unit.
-
-
--mm44--ssiinnggllee--oonnllyy
Generate code for the SH4 with a floating-point unit that only
-
supports single-precision arithmetic.
-
--mm44--ssiinnggllee
Generate code for the SH4 assuming the floating-point unit is in
-
single-precision mode by default.
-
--mm44
Generate code for the SH4.
-
-
--mm44aa--nnooffppuu
Generate code for the SH4al-dsp, or for a SH4a in such a way that the
-
floating-point unit is not used.
-
--mm44aa--ssiinnggllee--oonnllyy
Generate code for the SH4a, in such a way that no double-precision
-
floating point operations are used.
-
--mm44aa--ssiinnggllee
Generate code for the SH4a assuming the floating-point unit is in
-
single-precision mode by default.
-
--mm44aa
Generate code for the SH4a.
-
-
--mm44aall
Same as --mm44aa--nnooffppuu, except that it implicitly passes
-
--ddsspp to the assembler. GCC doesn't generate any DSP
instructions at the moment.
-
--mmbb
Compile code for the processor in big endian mode.
-
-
--mmll
Compile code for the processor in little endian mode.
-
-
--mmddaalliiggnn
Align doubles at 64-bit boundaries. Note that this changes the calling
-
conventions, and thus some functions from the standard C library will
not work unless you recompile it first with --mmddaalliiggnn.
-
--mmrreellaaxx
Shorten some address references at link time, when possible; uses the
-
linker option --rreellaaxx.
-
--mmbbiiggttaabbllee
Use 32-bit offsets in "switch" tables. The default is to use
-
16-bit offsets.
-
--mmffmmoovvdd
Enable the use of the instruction "fmovd".
-
-
--mmhhiittaacchhii
Comply with the calling conventions defined by Renesas.
-
-
--mmrreenneessaass
Comply with the calling conventions defined by Renesas.
-
-
--mmnnoo--rreenneessaass
Comply with the calling conventions defined for GCC before the Renesas
-
conventions were available. This option is the default for all
targets of the SH toolchain except for sshh--ssyymmbbiiaanneellff.
-
--mmnnoommaaccssaavvee
Mark the "MAC" register as call-clobbered, even if
-
--mmhhiittaacchhii is given.
-
--mmiieeeeee
Increase IEEE-compliance of floating-point code.
-
At the moment, this is equivalent to --ffnnoo--ffiinniittee--mmaatthh--oonnllyy.
When generating 16 bit SH opcodes, getting IEEE-conforming results for
comparisons of NANs / infinities incurs extra overhead in every
floating point comparison, therefore the default is set to
--ffffiinniittee--mmaatthh--oonnllyy.
-
--mmiissiizzee
Dump instruction size and location in the assembly code.
-
-
--mmppaaddssttrruucctt
This option is deprecated. It pads structures to multiple of 4 bytes,
-
which is incompatible with the SH ABI.
-
--mmssppaaccee
Optimize for space instead of speed. Implied by --OOss.
-
-
--mmpprreeffeerrggoott
When generating position-independent code, emit function calls using
-
the Global Offset Table instead of the Procedure Linkage Table.
-
--mmuusseerrmmooddee
Generate a library function call to invalidate instruction cache
-
entries, after fixing up a trampoline. This library function call
doesn't assume it can write to the whole memory address space. This
is the default when the target is "sh-*-linux*".
-
--mmuullttccoosstt==_n_u_m_b_e_r
Set the cost to assume for a multiply insn.
-
-
--mmddiivv==_s_t_r_a_t_e_g_y
Set the division strategy to use for SHmedia code. _s_t_r_a_t_e_g_y must be
-
one of: call, call2, fp, inv, inv:minlat, inv20u, inv20l, inv:call,
inv:call2, inv:fp .
"fp" performs the operation in floating point. This has a very high latency,
but needs only a few instructions, so it might be a good choice if
your code has enough easily exploitable ILP to allow the compiler to
schedule the floating point instructions together with other instructions.
Division by zero causes a floating point exception.
"inv" uses integer operations to calculate the inverse of the divisor,
and then multiplies the dividend with the inverse. This strategy allows
cse and hoisting of the inverse calculation. Division by zero calculates
an unspecified result, but does not trap.
"inv:minlat" is a variant of "inv" where if no cse / hoisting opportunities
have been found, or if the entire operation has been hoisted to the same
place, the last stages of the inverse calculation are intertwined with the
final multiply to reduce the overall latency, at the expense of using a few
more instructions, and thus offering fewer scheduling opportunities with
other code.
"call" calls a library function that usually implements the inv:minlat
strategy.
This gives high code density for m5-*media-nofpu compilations.
"call2" uses a different entry point of the same library function, where it
assumes that a pointer to a lookup table has already been set up, which
exposes the pointer load to cse / code hoisting optimizations.
"inv:call", "inv:call2" and "inv:fp" all use the "inv" algorithm for initial
code generation, but if the code stays unoptimized, revert to the "call",
"call2", or "fp" strategies, respectively. Note that the
potentially-trapping side effect of division by zero is carried by a
separate instruction, so it is possible that all the integer instructions
are hoisted out, but the marker for the side effect stays where it is.
A recombination to fp operations or a call is not possible in that case.
"inv20u" and "inv20l" are variants of the "inv:minlat" strategy. In the case
that the inverse calculation was nor separated from the multiply, they speed
up division where the dividend fits into 20 bits (plus sign where applicable),
by inserting a test to skip a number of operations in this case; this test
slows down the case of larger dividends. inv20u assumes the case of a such
a small dividend to be unlikely, and inv20l assumes it to be likely.
-
--mmddiivvssii33__lliibbffuunncc==_n_a_m_e
Set the name of the library function used for 32 bit signed division to
-
_n_a_m_e. This only affect the name used in the call and inv:call
division strategies, and the compiler will still expect the same
sets of input/output/clobbered registers as if this option was not present.
-
--mmaaddjjuusstt--uunnrroollll
Throttle unrolling to avoid thrashing target registers.
-
This option only has an effect if the gcc code base supports the
TARGET_ADJUST_UNROLL_MAX target hook.
-
--mmiinnddeexxeedd--aaddddrreessssiinngg
Enable the use of the indexed addressing mode for SHmedia32/SHcompact.
-
This is only safe if the hardware and/or OS implement 32 bit wrap-around
semantics for the indexed addressing mode. The architecture allows the
implementation of processors with 64 bit MMU, which the OS could use to
get 32 bit addressing, but since no current hardware implementation supports
this or any other way to make the indexed addressing mode safe to use in
the 32 bit ABI, the default is -mno-indexed-addressing.
-
--mmggeettttrrccoosstt==_n_u_m_b_e_r
Set the cost assumed for the gettr instruction to _n_u_m_b_e_r.
-
The default is 2 if --mmpptt--ffiixxeedd is in effect, 100 otherwise.
-
--mmpptt--ffiixxeedd
Assume pt* instructions won't trap. This will generally generate better
-
scheduled code, but is unsafe on current hardware. The current architecture
definition says that ptabs and ptrel trap when the target anded with 3 is 3.
This has the unintentional effect of making it unsafe to schedule ptabs /
ptrel before a branch, or hoist it out of a loop. For example,
__do_global_ctors, a part of libgcc that runs constructors at program
startup, calls functions in a list which is delimited by -1. With the
-mpt-fixed option, the ptabs will be done before testing against -1.
That means that all the constructors will be run a bit quicker, but when
the loop comes to the end of the list, the program crashes because ptabs
loads -1 into a target register. Since this option is unsafe for any
hardware implementing the current architecture specification, the default
is -mno-pt-fixed. Unless the user specifies a specific cost with
--mmggeettttrrccoosstt, -mno-pt-fixed also implies --mmggeettttrrccoosstt==110000;
this deters register allocation using target registers for storing
ordinary integers.
-
--mmiinnvvaalliidd--ssyymmbboollss
Assume symbols might be invalid. Ordinary function symbols generated by
-
the compiler will always be valid to load with movi/shori/ptabs or
movi/shori/ptrel, but with assembler and/or linker tricks it is possible
to generate symbols that will cause ptabs / ptrel to trap.
This option is only meaningful when --mmnnoo--pptt--ffiixxeedd is in effect.
It will then prevent cross-basic-block cse, hoisting and most scheduling
of symbol loads. The default is --mmnnoo--iinnvvaalliidd--ssyymmbboollss.
_S_P_A_R_C _O_p_t_i_o_n_s
These --mm options are supported on the SPARC:
-
--mmnnoo--aapppp--rreeggss
-
-
--mmaapppp--rreeggss
Specify --mmaapppp--rreeggss to generate output using the global registers
-
2 through 4, which the SPARC SVR4 ABI reserves for applications. This
is the default.
To be fully SVR4 ABI compliant at the cost of some performance loss,
specify --mmnnoo--aapppp--rreeggss. You should compile libraries and system
software with this option.
-
--mmffppuu
-
-
--mmhhaarrdd--ffllooaatt
Generate output containing floating point instructions. This is the
-
default.
-
--mmnnoo--ffppuu
-
-
--mmssoofftt--ffllooaatt
Generate output containing library calls for floating point.
-
WWaarrnniinngg:: the requisite libraries are not available for all SPARC
targets. Normally the facilities of the machine's usual C compiler are
used, but this cannot be done directly in cross-compilation. You must make
your own arrangements to provide suitable library functions for
cross-compilation. The embedded targets ssppaarrcc--**--aaoouutt and
ssppaarrcclliittee--**--** do provide software floating point support.
--mmssoofftt--ffllooaatt changes the calling convention in the output file;
therefore, it is only useful if you compile _a_l_l of a program with
this option. In particular, you need to compile _l_i_b_g_c_c_._a, the
library that comes with GCC, with --mmssoofftt--ffllooaatt in order for
this to work.
-
--mmhhaarrdd--qquuaadd--ffllooaatt
Generate output containing quad-word (long double) floating point
-
instructions.
-
--mmssoofftt--qquuaadd--ffllooaatt
Generate output containing library calls for quad-word (long double)
-
floating point instructions. The functions called are those specified
in the SPARC ABI. This is the default.
As of this writing, there are no SPARC implementations that have hardware
support for the quad-word floating point instructions. They all invoke
a trap handler for one of these instructions, and then the trap handler
emulates the effect of the instruction. Because of the trap handler overhead,
this is much slower than calling the ABI library routines. Thus the
--mmssoofftt--qquuaadd--ffllooaatt option is the default.
-
--mmnnoo--uunnaalliiggnneedd--ddoouubblleess
-
-
--mmuunnaalliiggnneedd--ddoouubblleess
Assume that doubles have 8 byte alignment. This is the default.
-
With --mmuunnaalliiggnneedd--ddoouubblleess, GCC assumes that doubles have 8 byte
alignment only if they are contained in another type, or if they have an
absolute address. Otherwise, it assumes they have 4 byte alignment.
Specifying this option avoids some rare compatibility problems with code
generated by other compilers. It is not the default because it results
in a performance loss, especially for floating point code.
-
--mmnnoo--ffaasstteerr--ssttrruuccttss
-
-
--mmffaasstteerr--ssttrruuccttss
With --mmffaasstteerr--ssttrruuccttss, the compiler assumes that structures
-
should have 8 byte alignment. This enables the use of pairs of
"ldd" and "std" instructions for copies in structure
assignment, in place of twice as many "ld" and "st" pairs.
However, the use of this changed alignment directly violates the SPARC
ABI. Thus, it's intended only for use on targets where the developer
acknowledges that their resulting code will not be directly in line with
the rules of the ABI.
-
--mmiimmppuurree--tteexxtt
--mmiimmppuurree--tteexxtt, used in addition to --sshhaarreedd, tells
-
the compiler to not pass --zz tteexxtt to the linker when linking a
shared object. Using this option, you can link position-dependent
code into a shared object.
--mmiimmppuurree--tteexxtt suppresses the "relocations remain against
allocatable but non-writable sections" linker error message.
However, the necessary relocations will trigger copy-on-write, and the
shared object is not actually shared across processes. Instead of
using --mmiimmppuurree--tteexxtt, you should compile all source code with
--ffppiicc or --ffPPIICC.
This option is only available on SunOS and Solaris.
-
--mmccppuu==_c_p_u___t_y_p_e
Set the instruction set, register set, and instruction scheduling parameters
-
for machine type _c_p_u___t_y_p_e. Supported values for _c_p_u___t_y_p_e are
vv77, ccyypprreessss, vv88, ssuuppeerrssppaarrcc, ssppaarrcclliittee,
ff993300, ff993344, hhyyppeerrssppaarrcc, ssppaarrcclliittee8866xx,
ssppaarrcclleett, ttsscc770011, vv99, uullttrraassppaarrcc, and
uullttrraassppaarrcc33.
Default instruction scheduling parameters are used for values that select
an architecture and not an implementation. These are vv77, vv88,
ssppaarrcclliittee, ssppaarrcclleett, vv99.
Here is a list of each supported architecture and their supported
implementations.
v7: cypress
v8: supersparc, hypersparc
sparclite: f930, f934, sparclite86x
sparclet: tsc701
v9: ultrasparc, ultrasparc3
By default (unless configured otherwise), GCC generates code for the V7
variant of the SPARC architecture. With --mmccppuu==ccyypprreessss, the compiler
additionally optimizes it for the Cypress CY7C602 chip, as used in the
SPARCStation/SPARCServer 3xx series. This is also appropriate for the older
SPARCStation 1, 2, IPX etc.
With --mmccppuu==vv88, GCC generates code for the V8 variant of the SPARC
architecture. The only difference from V7 code is that the compiler emits
the integer multiply and integer divide instructions which exist in SPARC-V8
but not in SPARC-V7. With --mmccppuu==ssuuppeerrssppaarrcc, the compiler additionally
optimizes it for the SuperSPARC chip, as used in the SPARCStation 10, 1000 and
2000 series.
With --mmccppuu==ssppaarrcclliittee, GCC generates code for the SPARClite variant of
the SPARC architecture. This adds the integer multiply, integer divide step
and scan ("ffs") instructions which exist in SPARClite but not in SPARC-V7.
With --mmccppuu==ff993300, the compiler additionally optimizes it for the
Fujitsu MB86930 chip, which is the original SPARClite, with no FPU. With
--mmccppuu==ff993344, the compiler additionally optimizes it for the Fujitsu
MB86934 chip, which is the more recent SPARClite with FPU.
With --mmccppuu==ssppaarrcclleett, GCC generates code for the SPARClet variant of
the SPARC architecture. This adds the integer multiply, multiply/accumulate,
integer divide step and scan ("ffs") instructions which exist in SPARClet
but not in SPARC-V7. With --mmccppuu==ttsscc770011, the compiler additionally
optimizes it for the TEMIC SPARClet chip.
With --mmccppuu==vv99, GCC generates code for the V9 variant of the SPARC
architecture. This adds 64-bit integer and floating-point move instructions,
3 additional floating-point condition code registers and conditional move
instructions. With --mmccppuu==uullttrraassppaarrcc, the compiler additionally
optimizes it for the Sun UltraSPARC I/II chips. With
--mmccppuu==uullttrraassppaarrcc33, the compiler additionally optimizes it for the
Sun UltraSPARC III chip.
-
--mmttuunnee==_c_p_u___t_y_p_e
Set the instruction scheduling parameters for machine type
-
_c_p_u___t_y_p_e, but do not set the instruction set or register set that the
option --mmccppuu==_c_p_u___t_y_p_e would.
The same values for --mmccppuu==_c_p_u___t_y_p_e can be used for
--mmttuunnee==_c_p_u___t_y_p_e, but the only useful values are those
that select a particular cpu implementation. Those are ccyypprreessss,
ssuuppeerrssppaarrcc, hhyyppeerrssppaarrcc, ff993300, ff993344,
ssppaarrcclliittee8866xx, ttsscc770011, uullttrraassppaarrcc, and
uullttrraassppaarrcc33.
-
--mmvv88pplluuss
-
-
--mmnnoo--vv88pplluuss
With --mmvv88pplluuss, GCC generates code for the SPARC-V8+ ABI. The
-
difference from the V8 ABI is that the global and out registers are
considered 64-bit wide. This is enabled by default on Solaris in 32-bit
mode for all SPARC-V9 processors.
-
--mmvviiss
-
-
--mmnnoo--vviiss
With --mmvviiss, GCC generates code that takes advantage of the UltraSPARC
-
Visual Instruction Set extensions. The default is --mmnnoo--vviiss.
These --mm options are supported in addition to the above
on SPARC-V9 processors in 64-bit environments:
-
--mmlliittttllee--eennddiiaann
Generate code for a processor running in little-endian mode. It is only
-
available for a few configurations and most notably not on Solaris and Linux.
-
--mm3322
-
-
--mm6644
Generate code for a 32-bit or 64-bit environment.
-
The 32-bit environment sets int, long and pointer to 32 bits.
The 64-bit environment sets int to 32 bits and long and pointer
to 64 bits.
-
--mmccmmooddeell==mmeeddllooww
Generate code for the Medium/Low code model: 64-bit addresses, programs
-
must be linked in the low 32 bits of memory. Programs can be statically
or dynamically linked.
-
--mmccmmooddeell==mmeeddmmiidd
Generate code for the Medium/Middle code model: 64-bit addresses, programs
-
must be linked in the low 44 bits of memory, the text and data segments must
be less than 2GB in size and the data segment must be located within 2GB of
the text segment.
-
--mmccmmooddeell==mmeeddaannyy
Generate code for the Medium/Anywhere code model: 64-bit addresses, programs
-
may be linked anywhere in memory, the text and data segments must be less
than 2GB in size and the data segment must be located within 2GB of the
text segment.
-
--mmccmmooddeell==eemmbbmmeeddaannyy
Generate code for the Medium/Anywhere code model for embedded systems:
-
64-bit addresses, the text and data segments must be less than 2GB in
size, both starting anywhere in memory (determined at link time). The
global register %g4 points to the base of the data segment. Programs
are statically linked and PIC is not supported.
-
--mmssttaacckk--bbiiaass
-
-
--mmnnoo--ssttaacckk--bbiiaass
With --mmssttaacckk--bbiiaass, GCC assumes that the stack pointer, and
-
frame pointer if present, are offset by -2047 which must be added back
when making stack frame references. This is the default in 64-bit mode.
Otherwise, assume no such offset is present.
These switches are supported in addition to the above on Solaris:
-
--tthhrreeaaddss
Add support for multithreading using the Solaris threads library. This
-
option sets flags for both the preprocessor and linker. This option does
not affect the thread safety of object code produced by the compiler or
that of libraries supplied with it.
-
--pptthhrreeaaddss
Add support for multithreading using the POSIX threads library. This
-
option sets flags for both the preprocessor and linker. This option does
not affect the thread safety of object code produced by the compiler or
that of libraries supplied with it.
-
--pptthhrreeaadd
This is a synonym for --pptthhrreeaaddss.
-
_O_p_t_i_o_n_s _f_o_r _S_y_s_t_e_m _V
These additional options are available on System V Release 4 for
compatibility with other compilers on those systems:
-
--GG
Create a shared object.
-
It is recommended that --ssyymmbboolliicc or --sshhaarreedd be used instead.
-
--QQyy
Identify the versions of each tool used by the compiler, in a
-
".ident" assembler directive in the output.
-
--QQnn
Refrain from adding ".ident" directives to the output file (this is
-
the default).
-
--YYPP,,_d_i_r_s
Search the directories _d_i_r_s, and no others, for libraries
-
specified with --ll.
-
--YYmm,,_d_i_r
Look in the directory _d_i_r to find the M4 preprocessor.
-
The assembler uses this option.
_T_M_S_3_2_0_C_3_x_/_C_4_x _O_p_t_i_o_n_s
These --mm options are defined for TMS320C3x/C4x implementations:
-
--mmccppuu==_c_p_u___t_y_p_e
Set the instruction set, register set, and instruction scheduling
-
parameters for machine type _c_p_u___t_y_p_e. Supported values for
_c_p_u___t_y_p_e are cc3300, cc3311, cc3322, cc4400, and
cc4444. The default is cc4400 to generate code for the
TMS320C40.
-
--mmbbiigg--mmeemmoorryy
-
-
--mmbbiigg
-
-
--mmssmmaallll--mmeemmoorryy
-
-
--mmssmmaallll
Generates code for the big or small memory model. The small memory
-
model assumed that all data fits into one 64K word page. At run-time
the data page (DP) register must be set to point to the 64K page
containing the .bss and .data program sections. The big memory model is
the default and requires reloading of the DP register for every direct
memory access.
-
--mmbbkk
-
-
--mmnnoo--bbkk
Allow (disallow) allocation of general integer operands into the block
-
count register BK.
-
--mmddbb
-
-
--mmnnoo--ddbb
Enable (disable) generation of code using decrement and branch,
-
DBcond(D), instructions. This is enabled by default for the C4x. To be
on the safe side, this is disabled for the C3x, since the maximum
iteration count on the C3x is 2^{23 + 1} (but who iterates loops more than
2^{23} times on the C3x?). Note that GCC will try to reverse a loop so
that it can utilize the decrement and branch instruction, but will give
up if there is more than one memory reference in the loop. Thus a loop
where the loop counter is decremented can generate slightly more
efficient code, in cases where the RPTB instruction cannot be utilized.
-
--mmddpp--iissrr--rreellooaadd
-
-
--mmppaarraannooiidd
Force the DP register to be saved on entry to an interrupt service
-
routine (ISR), reloaded to point to the data section, and restored on
exit from the ISR. This should not be required unless someone has
violated the small memory model by modifying the DP register, say within
an object library.
-
--mmmmppyyii
-
-
--mmnnoo--mmppyyii
For the C3x use the 24-bit MPYI instruction for integer multiplies
-
instead of a library call to guarantee 32-bit results. Note that if one
of the operands is a constant, then the multiplication will be performed
using shifts and adds. If the --mmmmppyyii option is not specified for the C3x,
then squaring operations are performed inline instead of a library call.
-
--mmffaasstt--ffiixx
-
-
--mmnnoo--ffaasstt--ffiixx
The C3x/C4x FIX instruction to convert a floating point value to an
-
integer value chooses the nearest integer less than or equal to the
floating point value rather than to the nearest integer. Thus if the
floating point number is negative, the result will be incorrectly
truncated an additional code is necessary to detect and correct this
case. This option can be used to disable generation of the additional
code required to correct the result.
-
--mmrrppttbb
-
-
--mmnnoo--rrppttbb
Enable (disable) generation of repeat block sequences using the RPTB
-
instruction for zero overhead looping. The RPTB construct is only used
for innermost loops that do not call functions or jump across the loop
boundaries. There is no advantage having nested RPTB loops due to the
overhead required to save and restore the RC, RS, and RE registers.
This is enabled by default with --OO22.
-
--mmrrppttss==_c_o_u_n_t
-
-
--mmnnoo--rrppttss
Enable (disable) the use of the single instruction repeat instruction
-
RPTS. If a repeat block contains a single instruction, and the loop
count can be guaranteed to be less than the value _c_o_u_n_t, GCC will
emit a RPTS instruction instead of a RPTB. If no value is specified,
then a RPTS will be emitted even if the loop count cannot be determined
at compile time. Note that the repeated instruction following RPTS does
not have to be reloaded from memory each iteration, thus freeing up the
CPU buses for operands. However, since interrupts are blocked by this
instruction, it is disabled by default.
-
--mmlloooopp--uunnssiiggnneedd
-
-
--mmnnoo--lloooopp--uunnssiiggnneedd
The maximum iteration count when using RPTS and RPTB (and DB on the C40)
-
is 2^{31 + 1} since these instructions test if the iteration count is
negative to terminate the loop. If the iteration count is unsigned
there is a possibility than the 2^{31 + 1} maximum iteration count may be
exceeded. This switch allows an unsigned iteration count.
-
--mmttii
Try to emit an assembler syntax that the TI assembler (asm30) is happy
-
with. This also enforces compatibility with the API employed by the TI
C3x C compiler. For example, long doubles are passed as structures
rather than in floating point registers.
-
--mmrreeggppaarrmm
-
-
--mmmmeemmppaarrmm
Generate code that uses registers (stack) for passing arguments to functions.
-
By default, arguments are passed in registers where possible rather
than by pushing arguments on to the stack.
-
--mmppaarraalllleell--iinnssnnss
-
-
--mmnnoo--ppaarraalllleell--iinnssnnss
Allow the generation of parallel instructions. This is enabled by
-
default with --OO22.
-
--mmppaarraalllleell--mmppyy
-
-
--mmnnoo--ppaarraalllleell--mmppyy
Allow the generation of MPY||ADD and MPY||SUB parallel instructions,
-
provided --mmppaarraalllleell--iinnssnnss is also specified. These instructions have
tight register constraints which can pessimize the code generation
of large functions.
_V_8_5_0 _O_p_t_i_o_n_s
These --mm options are defined for V850 implementations:
-
--mmlloonngg--ccaallllss
-
-
--mmnnoo--lloonngg--ccaallllss
Treat all calls as being far away (near). If calls are assumed to be
-
far away, the compiler will always load the functions address up into a
register, and call indirect through the pointer.
-
--mmnnoo--eepp
-
-
--mmeepp
Do not optimize (do optimize) basic blocks that use the same index
-
pointer 4 or more times to copy pointer into the "ep" register, and
use the shorter "sld" and "sst" instructions. The --mmeepp
option is on by default if you optimize.
-
--mmnnoo--pprroolloogg--ffuunnccttiioonn
-
-
--mmpprroolloogg--ffuunnccttiioonn
Do not use (do use) external functions to save and restore registers
-
at the prologue and epilogue of a function. The external functions
are slower, but use less code space if more than one function saves
the same number of registers. The --mmpprroolloogg--ffuunnccttiioonn option
is on by default if you optimize.
-
--mmssppaaccee
Try to make the code as small as possible. At present, this just turns
-
on the --mmeepp and --mmpprroolloogg--ffuunnccttiioonn options.
-
--mmttddaa==_n
Put static or global variables whose size is _n bytes or less into
-
the tiny data area that register "ep" points to. The tiny data
area can hold up to 256 bytes in total (128 bytes for byte references).
-
--mmssddaa==_n
Put static or global variables whose size is _n bytes or less into
-
the small data area that register "gp" points to. The small data
area can hold up to 64 kilobytes.
-
--mmzzddaa==_n
Put static or global variables whose size is _n bytes or less into
-
the first 32 kilobytes of memory.
-
--mmvv885500
Specify that the target processor is the V850.
-
-
--mmbbiigg--sswwiittcchh
Generate code suitable for big switch tables. Use this option only if
-
the assembler/linker complain about out of range branches within a switch
table.
-
--mmaapppp--rreeggss
This option will cause r2 and r5 to be used in the code generated by
-
the compiler. This setting is the default.
-
--mmnnoo--aapppp--rreeggss
This option will cause r2 and r5 to be treated as fixed registers.
-
-
--mmvv885500ee11
Specify that the target processor is the V850E1. The preprocessor
-
constants ____vv885500ee11____ and ____vv885500ee____ will be defined if
this option is used.
-
--mmvv885500ee
Specify that the target processor is the V850E. The preprocessor
-
constant ____vv885500ee____ will be defined if this option is used.
If neither --mmvv885500 nor --mmvv885500ee nor --mmvv885500ee11
are defined then a default target processor will be chosen and the
relevant ____vv885500**____ preprocessor constant will be defined.
The preprocessor constants ____vv885500 and ____vv885511____ are always
defined, regardless of which processor variant is the target.
-
--mmddiissaabbllee--ccaalllltt
This option will suppress generation of the CALLT instruction for the
-
v850e and v850e1 flavors of the v850 architecture. The default is
--mmnnoo--ddiissaabbllee--ccaalllltt which allows the CALLT instruction to be used.
_V_A_X _O_p_t_i_o_n_s
These --mm options are defined for the VAX:
-
--mmuunniixx
Do not output certain jump instructions ("aobleq" and so on)
-
that the Unix assembler for the VAX cannot handle across long
ranges.
-
--mmggnnuu
Do output those jump instructions, on the assumption that you
-
will assemble with the GNU assembler.
-
--mmgg
Output code for g-format floating point numbers instead of d-format.
-
_x_8_6_-_6_4 _O_p_t_i_o_n_s
These are listed under
_X_s_t_o_r_m_y_1_6 _O_p_t_i_o_n_s
These options are defined for Xstormy16:
-
--mmssiimm
Choose startup files and linker script suitable for the simulator.
-
_X_t_e_n_s_a _O_p_t_i_o_n_s
These options are supported for Xtensa targets:
-
--mmccoonnsstt1166
-
-
--mmnnoo--ccoonnsstt1166
Enable or disable use of "CONST16" instructions for loading
-
constant values. The "CONST16" instruction is currently not a
standard option from Tensilica. When enabled, "CONST16"
instructions are always used in place of the standard "L32R"
instructions. The use of "CONST16" is enabled by default only if
the "L32R" instruction is not available.
-
--mmffuusseedd--mmaadddd
-
-
--mmnnoo--ffuusseedd--mmaadddd
Enable or disable use of fused multiply/add and multiply/subtract
-
instructions in the floating-point option. This has no effect if the
floating-point option is not also enabled. Disabling fused multiply/add
and multiply/subtract instructions forces the compiler to use separate
instructions for the multiply and add/subtract operations. This may be
desirable in some cases where strict IEEE 754-compliant results are
required: the fused multiply add/subtract instructions do not round the
intermediate result, thereby producing results with _m_o_r_e bits of
precision than specified by the IEEE standard. Disabling fused multiply
add/subtract instructions also ensures that the program output is not
sensitive to the compiler's ability to combine multiply and add/subtract
operations.
-
--mmtteexxtt--sseeccttiioonn--lliitteerraallss
-
-
--mmnnoo--tteexxtt--sseeccttiioonn--lliitteerraallss
Control the treatment of literal pools. The default is
-
--mmnnoo--tteexxtt--sseeccttiioonn--lliitteerraallss, which places literals in a separate
section in the output file. This allows the literal pool to be placed
in a data RAM/ROM, and it also allows the linker to combine literal
pools from separate object files to remove redundant literals and
improve code size. With --mmtteexxtt--sseeccttiioonn--lliitteerraallss, the literals
are interspersed in the text section in order to keep them as close as
possible to their references. This may be necessary for large assembly
files.
-
--mmttaarrggeett--aalliiggnn
-
-
--mmnnoo--ttaarrggeett--aalliiggnn
When this option is enabled, GCC instructs the assembler to
-
automatically align instructions to reduce branch penalties at the
expense of some code density. The assembler attempts to widen density
instructions to align branch targets and the instructions following call
instructions. If there are not enough preceding safe density
instructions to align a target, no widening will be performed. The
default is --mmttaarrggeett--aalliiggnn. These options do not affect the
treatment of auto-aligned instructions like "LOOP", which the
assembler will always align, either by widening density instructions or
by inserting no-op instructions.
-
--mmlloonnggccaallllss
-
-
--mmnnoo--lloonnggccaallllss
When this option is enabled, GCC instructs the assembler to translate
-
direct calls to indirect calls unless it can determine that the target
of a direct call is in the range allowed by the call instruction. This
translation typically occurs for calls to functions in other source
files. Specifically, the assembler translates a direct "CALL"
instruction into an "L32R" followed by a "CALLX" instruction.
The default is --mmnnoo--lloonnggccaallllss. This option should be used in
programs where the call target can potentially be out of range. This
option is implemented in the assembler, not the compiler, so the
assembly code generated by GCC will still show direct call
instructions---look at the disassembled object code to see the actual
instructions. Note that the assembler will use an indirect call for
every cross-file call, not just those that really will be out of range.
_z_S_e_r_i_e_s _O_p_t_i_o_n_s
These are listed under
OOppttiioonnss ffoorr CCooddee GGeenneerraattiioonn CCoonnvveennttiioonnss
These machine-independent options control the interface conventions
used in code generation.
Most of them have both positive and negative forms; the negative form
of --ffffoooo would be --ffnnoo--ffoooo. In the table below, only
one of the forms is listed---the one which is not the default. You
can figure out the other form by either removing nnoo-- or adding
it.
-
--ffbboouunnddss--cchheecckk
For front-ends that support it, generate additional code to check that
-
indices used to access arrays are within the declared range. This is
currently only supported by the Java and Fortran 77 front-ends, where
this option defaults to true and false respectively.
-
--ffttrraappvv
This option generates traps for signed overflow on addition, subtraction,
-
multiplication operations.
-
--ffwwrraappvv
This option instructs the compiler to assume that signed arithmetic
-
overflow of addition, subtraction and multiplication wraps around
using twos-complement representation. This flag enables some optimizations
and disables others. This option is enabled by default for the Java
front-end, as required by the Java language specification.
-
--ffeexxcceeppttiioonnss
Enable exception handling. Generates extra code needed to propagate
-
exceptions. For some targets, this implies GCC will generate frame
unwind information for all functions, which can produce significant data
size overhead, although it does not affect execution. If you do not
specify this option, GCC will enable it by default for languages like
C++ which normally require exception handling, and disable it for
languages like C that do not normally require it. However, you may need
to enable this option when compiling C code that needs to interoperate
properly with exception handlers written in C++. You may also wish to
disable this option if you are compiling older C++ programs that don't
use exception handling.
-
--ffnnoonn--ccaallll--eexxcceeppttiioonnss
Generate code that allows trapping instructions to throw exceptions.
-
Note that this requires platform-specific runtime support that does
not exist everywhere. Moreover, it only allows _t_r_a_p_p_i_n_g
instructions to throw exceptions, i.e. memory references or floating
point instructions. It does not allow exceptions to be thrown from
arbitrary signal handlers such as "SIGALRM".
-
--ffuunnwwiinndd--ttaabblleess
Similar to --ffeexxcceeppttiioonnss, except that it will just generate any needed
-
static data, but will not affect the generated code in any other way.
You will normally not enable this option; instead, a language processor
that needs this handling would enable it on your behalf.
-
--ffaassyynncchhrroonnoouuss--uunnwwiinndd--ttaabblleess
Generate unwind table in dwarf2 format, if supported by target machine. The
-
table is exact at each instruction boundary, so it can be used for stack
unwinding from asynchronous events (such as debugger or garbage collector).
-
--ffppcccc--ssttrruucctt--rreettuurrnn
Return "short" "struct" and "union" values in memory like
-
longer ones, rather than in registers. This convention is less
efficient, but it has the advantage of allowing intercallability between
GCC-compiled files and files compiled with other compilers, particularly
the Portable C Compiler (pcc).
The precise convention for returning structures in memory depends
on the target configuration macros.
Short structures and unions are those whose size and alignment match
that of some integer type.
WWaarrnniinngg:: code compiled with the --ffppcccc--ssttrruucctt--rreettuurrnn
switch is not binary compatible with code compiled with the
--ffrreegg--ssttrruucctt--rreettuurrnn switch.
Use it to conform to a non-default application binary interface.
-
--ffrreegg--ssttrruucctt--rreettuurrnn
Return "struct" and "union" values in registers when possible.
-
This is more efficient for small structures than
--ffppcccc--ssttrruucctt--rreettuurrnn.
If you specify neither --ffppcccc--ssttrruucctt--rreettuurrnn nor
--ffrreegg--ssttrruucctt--rreettuurrnn, GCC defaults to whichever convention is
standard for the target. If there is no standard convention, GCC
defaults to --ffppcccc--ssttrruucctt--rreettuurrnn, except on targets where GCC is
the principal compiler. In those cases, we can choose the standard, and
we chose the more efficient register return alternative.
WWaarrnniinngg:: code compiled with the --ffrreegg--ssttrruucctt--rreettuurrnn
switch is not binary compatible with code compiled with the
--ffppcccc--ssttrruucctt--rreettuurrnn switch.
Use it to conform to a non-default application binary interface.
-
--ffsshhoorrtt--eennuummss
Allocate to an "enum" type only as many bytes as it needs for the
-
declared range of possible values. Specifically, the "enum" type
will be equivalent to the smallest integer type which has enough room.
WWaarrnniinngg:: the --ffsshhoorrtt--eennuummss switch causes GCC to generate
code that is not binary compatible with code generated without that switch.
Use it to conform to a non-default application binary interface.
-
--ffsshhoorrtt--ddoouubbllee
Use the same size for "double" as for "float".
-
WWaarrnniinngg:: the --ffsshhoorrtt--ddoouubbllee switch causes GCC to generate
code that is not binary compatible with code generated without that switch.
Use it to conform to a non-default application binary interface.
-
--ffsshhoorrtt--wwcchhaarr
Override the underlying type for wwcchhaarr__tt to be sshhoorrtt
<>
uunnssiiggnneedd iinntt instead of the default for the target. This option is
useful for building programs to run under WINE.
WWaarrnniinngg:: the --ffsshhoorrtt--wwcchhaarr switch causes GCC to generate
code that is not binary compatible with code generated without that switch.
Use it to conform to a non-default application binary interface.
-
--ffsshhaarreedd--ddaattaa
Requests that the data and non-"const" variables of this
-
compilation be shared data rather than private data. The distinction
makes sense only on certain operating systems, where shared data is
shared between processes running the same program, while private data
exists in one copy per process.
-
--ffnnoo--ccoommmmoonn
In C, allocate even uninitialized global variables in the data section of the
-
object file, rather than generating them as common blocks. This has the
effect that if the same variable is declared (without "extern") in
two different compilations, you will get an error when you link them.
The only reason this might be useful is if you wish to verify that the
program will work on other systems which always work this way.
-
--ffnnoo--iiddeenntt
Ignore the ##iiddeenntt directive.
-
-
--ffiinnhhiibbiitt--ssiizzee--ddiirreeccttiivvee
Don't output a ".size" assembler directive, or anything else that
-
would cause trouble if the function is split in the middle, and the
two halves are placed at locations far apart in memory. This option is
used when compiling _c_r_t_s_t_u_f_f_._c; you should not need to use it
for anything else.
-
--ffvveerrbboossee--aassmm
Put extra commentary information in the generated assembly code to
-
make it more readable. This option is generally only of use to those
who actually need to read the generated assembly code (perhaps while
debugging the compiler itself).
--ffnnoo--vveerrbboossee--aassmm, the default, causes the
extra information to be omitted and is useful when comparing two assembler
files.
-
--ffppiicc
Generate position-independent code (PIC) suitable for use in a shared
-
library, if supported for the target machine. Such code accesses all
constant addresses through a global offset table (GOT). The dynamic
loader resolves the GOT entries when the program starts (the dynamic
loader is not part of GCC; it is part of the operating system). If
the GOT size for the linked executable exceeds a machine-specific
maximum size, you get an error message from the linker indicating that
--ffppiicc does not work; in that case, recompile with --ffPPIICC
instead. (These maximums are 8k on the SPARC and 32k
on the m68k and RS/6000. The 386 has no such limit.)
Position-independent code requires special support, and therefore works
only on certain machines. For the 386, GCC supports PIC for System V
but not for the Sun 386i. Code generated for the IBM RS/6000 is always
position-independent.
-
--ffPPIICC
If supported for the target machine, emit position-independent code,
-
suitable for dynamic linking and avoiding any limit on the size of the
global offset table. This option makes a difference on the m68k,
PowerPC and SPARC.
Position-independent code requires special support, and therefore works
only on certain machines.
-
--ffppiiee
-
-
--ffPPIIEE
These options are similar to --ffppiicc and --ffPPIICC, but
-
generated position independent code can be only linked into executables.
Usually these options are used when --ppiiee GCC option will be
used during linking.
-
--ffnnoo--jjuummpp--ttaabblleess
Do not use jump tables for switch statements even where it would be
-
more efficient than other code generation strategies. This option is
of use in conjunction with --ffppiicc or --ffPPIICC for
building code which forms part of a dynamic linker and cannot
reference the address of a jump table. On some targets, jump tables
do not require a GOT and this option is not needed.
-
--ffffiixxeedd--_r_e_g
Treat the register named _r_e_g as a fixed register; generated code
-
should never refer to it (except perhaps as a stack pointer, frame
pointer or in some other fixed role).
_r_e_g must be the name of a register. The register names accepted
are machine-specific and are defined in the "REGISTER_NAMES"
macro in the machine description macro file.
This flag does not have a negative form, because it specifies a
three-way choice.
-
--ffccaallll--uusseedd--_r_e_g
Treat the register named _r_e_g as an allocable register that is
-
clobbered by function calls. It may be allocated for temporaries or
variables that do not live across a call. Functions compiled this way
will not save and restore the register _r_e_g.
It is an error to used this flag with the frame pointer or stack pointer.
Use of this flag for other registers that have fixed pervasive roles in
the machine's execution model will produce disastrous results.
This flag does not have a negative form, because it specifies a
three-way choice.
-
--ffccaallll--ssaavveedd--_r_e_g
Treat the register named _r_e_g as an allocable register saved by
-
functions. It may be allocated even for temporaries or variables that
live across a call. Functions compiled this way will save and restore
the register _r_e_g if they use it.
It is an error to used this flag with the frame pointer or stack pointer.
Use of this flag for other registers that have fixed pervasive roles in
the machine's execution model will produce disastrous results.
A different sort of disaster will result from the use of this flag for
a register in which function values may be returned.
This flag does not have a negative form, because it specifies a
three-way choice.
-
--ffppaacckk--ssttrruucctt[[==_n]]
Without a value specified, pack all structure members together without
-
holes. When a value is specified (which must be a small power of two), pack
structure members according to this value, representing the maximum
alignment (that is, objects with default alignment requirements larger than
this will be output potentially unaligned at the next fitting location.
WWaarrnniinngg:: the --ffppaacckk--ssttrruucctt switch causes GCC to generate
code that is not binary compatible with code generated without that switch.
Additionally, it makes the code suboptimal.
Use it to conform to a non-default application binary interface.
-
--ffiinnssttrruummeenntt--ffuunnccttiioonnss
Generate instrumentation calls for entry and exit to functions. Just
-
after function entry and just before function exit, the following
profiling functions will be called with the address of the current
function and its call site. (On some platforms,
"__builtin_return_address" does not work beyond the current
function, so the call site information may not be available to the
profiling functions otherwise.)
void __cyg_profile_func_enter (void *this_fn,
void *call_site);
void __cyg_profile_func_exit (void *this_fn,
void *call_site);
The first argument is the address of the start of the current function,
which may be looked up exactly in the symbol table.
This instrumentation is also done for functions expanded inline in other
functions. The profiling calls will indicate where, conceptually, the
inline function is entered and exited. This means that addressable
versions of such functions must be available. If all your uses of a
function are expanded inline, this may mean an additional expansion of
code size. If you use eexxtteerrnn iinnlliinnee in your C code, an
addressable version of such functions must be provided. (This is
normally the case anyways, but if you get lucky and the optimizer always
expands the functions inline, you might have gotten away without
providing static copies.)
A function may be given the attribute "no_instrument_function", in
which case this instrumentation will not be done. This can be used, for
example, for the profiling functions listed above, high-priority
interrupt routines, and any functions from which the profiling functions
cannot safely be called (perhaps signal handlers, if the profiling
routines generate output or allocate memory).
-
--ffssttaacckk--cchheecckk
Generate code to verify that you do not go beyond the boundary of the
-
stack. You should specify this flag if you are running in an
environment with multiple threads, but only rarely need to specify it in
a single-threaded environment since stack overflow is automatically
detected on nearly all systems if there is only one stack.
Note that this switch does not actually cause checking to be done; the
operating system must do that. The switch causes generation of code
to ensure that the operating system sees the stack being extended.
-
--ffssttaacckk--lliimmiitt--rreeggiisstteerr==_r_e_g
-
-
--ffssttaacckk--lliimmiitt--ssyymmbbooll==_s_y_m
-
-
--ffnnoo--ssttaacckk--lliimmiitt
Generate code to ensure that the stack does not grow beyond a certain value,
-
either the value of a register or the address of a symbol. If the stack
would grow beyond the value, a signal is raised. For most targets,
the signal is raised before the stack overruns the boundary, so
it is possible to catch the signal without taking special precautions.
For instance, if the stack starts at absolute address 00xx8800000000000000
and grows downwards, you can use the flags
--ffssttaacckk--lliimmiitt--ssyymmbbooll==____ssttaacckk__lliimmiitt and
--WWll,,----ddeeffssyymm,,____ssttaacckk__lliimmiitt==00xx77ffffee00000000 to enforce a stack limit
of 128KB. Note that this may only work with the GNU linker.
-
--ffaarrgguummeenntt--aalliiaass
-
-
--ffaarrgguummeenntt--nnooaalliiaass
-
-
--ffaarrgguummeenntt--nnooaalliiaass--gglloobbaall
Specify the possible relationships among parameters and between
-
parameters and global data.
--ffaarrgguummeenntt--aalliiaass specifies that arguments (parameters) may
alias each other and may alias global storage.--ffaarrgguummeenntt--nnooaalliiaass specifies that arguments do not alias
each other, but may alias global storage.--ffaarrgguummeenntt--nnooaalliiaass--gglloobbaall specifies that arguments do not
alias each other and do not alias global storage.
Each language will automatically use whatever option is required by
the language standard. You should not need to use these options yourself.
-
--fflleeaaddiinngg--uunnddeerrssccoorree
This option and its counterpart, --ffnnoo--lleeaaddiinngg--uunnddeerrssccoorree, forcibly
-
change the way C symbols are represented in the object file. One use
is to help link with legacy assembly code.
WWaarrnniinngg:: the --fflleeaaddiinngg--uunnddeerrssccoorree switch causes GCC to
generate code that is not binary compatible with code generated without that
switch. Use it to conform to a non-default application binary interface.
Not all targets provide complete support for this switch.
-
--ffttllss--mmooddeell==_m_o_d_e_l
Alter the thread-local storage model to be used.
-
The _m_o_d_e_l argument should be one of "global-dynamic",
"local-dynamic", "initial-exec" or "local-exec".
The default without --ffppiicc is "initial-exec"; with
--ffppiicc the default is "global-dynamic".
-
--ffvviissiibbiilliittyy==_d_e_f_a_u_l_t_|_i_n_t_e_r_n_a_l_|_h_i_d_d_e_n_|_p_r_o_t_e_c_t_e_d
Set the default ELF image symbol visibility to the specified option---all
-
symbols will be marked with this unless overridden within the code.
Using this feature can very substantially improve linking and
load times of shared object libraries, produce more optimized
code, provide near-perfect API export and prevent symbol clashes.
It is ssttrroonnggllyy recommended that you use this in any shared objects
you distribute.
Despite the nomenclature, "default" always means public ie;
available to be linked against from outside the shared object.
"protected" and "internal" are pretty useless in real-world
usage so the only other commonly used option will be "hidden".
The default if --ffvviissiibbiilliittyy isn't specified is
"default", i.e., make every
symbol public---this causes the same behavior as previous versions of
GCC.
A good explanation of the benefits offered by ensuring ELF
symbols have the correct visibility is given by "How To Write
Shared Libraries" by Ulrich Drepper (which can be found at
)---however a superior
solution made possible by this option to marking things hidden when
the default is public is to make the default hidden and mark things
public. This is the norm with DLL's on Windows and with --ffvviissiibbiilliittyy==hhiiddddeenn
and "__attribute__ ((visibility("default")))" instead of
"__declspec(dllexport)" you get almost identical semantics with
identical syntax. This is a great boon to those working with
cross-platform projects.
For those adding visibility support to existing code, you may find
##pprraaggmmaa GGCCCC vviissiibbiilliittyy of use. This works by you enclosing
the declarations you wish to set visibility for with (for example)
##pprraaggmmaa GGCCCC vviissiibbiilliittyy ppuusshh((hhiiddddeenn)) and
##pprraaggmmaa GGCCCC vviissiibbiilliittyy ppoopp.
Bear in mind that symbol visibility should be viewed aass
ppaarrtt ooff tthhee AAPPII iinntteerrffaaccee ccoonnttrraacctt and thus all new code should
always specify visibility when it is not the default ie; declarations
only for use within the local DSO should aallwwaayyss be marked explicitly
as hidden as so to avoid PLT indirection overheads---making this
abundantly clear also aids readability and self-documentation of the code.
Note that due to ISO C++ specification requirements, operator new and
operator delete must always be of default visibility.
An overview of these techniques, their benefits and how to use them
is at .
ENVIRONMENT
This section describes several environment variables that affect how GCC
operates. Some of them work by specifying directories or prefixes to use
when searching for various kinds of files. Some are used to specify other
aspects of the compilation environment.
Note that you can also specify places to search using options such as
--BB, --II and --LL. These
take precedence over places specified using environment variables, which
in turn take precedence over those specified by the configuration of GCC.
-
LLAANNGG
-
-
LLCC__CCTTYYPPEE
-
-
LLCC__MMEESSSSAAGGEESS
-
-
LLCC__AALLLL
These environment variables control the way that GCC uses
-
localization information that allow GCC to work with different
national conventions. GCC inspects the locale categories
LLCC__CCTTYYPPEE and LLCC__MMEESSSSAAGGEESS if it has been configured to do
so. These locale categories can be set to any value supported by your
installation. A typical value is eenn__GGBB..UUTTFF--88 for English in the United
Kingdom encoded in UTF-8.
The LLCC__CCTTYYPPEE environment variable specifies character
classification. GCC uses it to determine the character boundaries in
a string; this is needed for some multibyte encodings that contain quote
and escape characters that would otherwise be interpreted as a string
end or escape.
The LLCC__MMEESSSSAAGGEESS environment variable specifies the language to
use in diagnostic messages.
If the LLCC__AALLLL environment variable is set, it overrides the value
of LLCC__CCTTYYPPEE and LLCC__MMEESSSSAAGGEESS; otherwise, LLCC__CCTTYYPPEE
and LLCC__MMEESSSSAAGGEESS default to the value of the LLAANNGG
environment variable. If none of these variables are set, GCC
defaults to traditional C English behavior.
-
TTMMPPDDIIRR
If TTMMPPDDIIRR is set, it specifies the directory to use for temporary
-
files. GCC uses temporary files to hold the output of one stage of
compilation which is to be used as input to the next stage: for example,
the output of the preprocessor, which is the input to the compiler
proper.
-
GGCCCC__EEXXEECC__PPRREEFFIIXX
If GGCCCC__EEXXEECC__PPRREEFFIIXX is set, it specifies a prefix to use in the
-
names of the subprograms executed by the compiler. No slash is added
when this prefix is combined with the name of a subprogram, but you can
specify a prefix that ends with a slash if you wish.
If GGCCCC__EEXXEECC__PPRREEFFIIXX is not set, GCC will attempt to figure out
an appropriate prefix to use based on the pathname it was invoked with.
If GCC cannot find the subprogram using the specified prefix, it
tries looking in the usual places for the subprogram.
The default value of GGCCCC__EEXXEECC__PPRREEFFIIXX is
_p_r_e_f_i_x_/_l_i_b_/_g_c_c_/ where _p_r_e_f_i_x is the value
of "prefix" when you ran the _c_o_n_f_i_g_u_r_e script.
Other prefixes specified with --BB take precedence over this prefix.
This prefix is also used for finding files such as _c_r_t_0_._o that are
used for linking.
In addition, the prefix is used in an unusual way in finding the
directories to search for header files. For each of the standard
directories whose name normally begins with //uussrr//llooccaall//lliibb//ggcccc
(more precisely, with the value of GGCCCC__IINNCCLLUUDDEE__DDIIRR), GCC tries
replacing that beginning with the specified prefix to produce an
alternate directory name. Thus, with --BBffoooo//, GCC will search
_f_o_o_/_b_a_r where it would normally search _/_u_s_r_/_l_o_c_a_l_/_l_i_b_/_b_a_r.
These alternate directories are searched first; the standard directories
come next.
-
CCOOMMPPIILLEERR__PPAATTHH
The value of CCOOMMPPIILLEERR__PPAATTHH is a colon-separated list of
-
directories, much like PPAATTHH. GCC tries the directories thus
specified when searching for subprograms, if it can't find the
subprograms using GGCCCC__EEXXEECC__PPRREEFFIIXX.
-
LLIIBBRRAARRYY__PPAATTHH
The value of LLIIBBRRAARRYY__PPAATTHH is a colon-separated list of
-
directories, much like PPAATTHH. When configured as a native compiler,
GCC tries the directories thus specified when searching for special
linker files, if it can't find them using GGCCCC__EEXXEECC__PPRREEFFIIXX. Linking
using GCC also uses these directories when searching for ordinary
libraries for the --ll option (but directories specified with
--LL come first).
-
LLAANNGG
This variable is used to pass locale information to the compiler. One way in
-
which this information is used is to determine the character set to be used
when character literals, string literals and comments are parsed in C and C++.
When the compiler is configured to allow multibyte characters,
the following values for LLAANNGG are recognized:
-
CC--JJIISS
Recognize JIS characters.
-
-
CC--SSJJIISS
Recognize SJIS characters.
-
-
CC--EEUUCCJJPP
Recognize EUCJP characters.
-
If LLAANNGG is not defined, or if it has some other value, then the
compiler will use mblen and mbtowc as defined by the default locale to
recognize and translate multibyte characters.
Some additional environments variables affect the behavior of the
preprocessor.
-
CCPPAATTHH
-
-
CC__IINNCCLLUUDDEE__PPAATTHH
-
-
CCPPLLUUSS__IINNCCLLUUDDEE__PPAATTHH
-
-
OOBBJJCC__IINNCCLLUUDDEE__PPAATTHH
Each variable's value is a list of directories separated by a special
-
character, much like PPAATTHH, in which to look for header files.
The special character, "PATH_SEPARATOR", is target-dependent and
determined at GCC build time. For Microsoft Windows-based targets it is a
semicolon, and for almost all other targets it is a colon.
CCPPAATTHH specifies a list of directories to be searched as if
specified with --II, but after any paths given with --II
options on the command line. This environment variable is used
regardless of which language is being preprocessed.
The remaining environment variables apply only when preprocessing the
particular language indicated. Each specifies a list of directories
to be searched as if specified with --iissyysstteemm, but after any
paths given with --iissyysstteemm options on the command line.
In all these variables, an empty element instructs the compiler to
search its current working directory. Empty elements can appear at the
beginning or end of a path. For instance, if the value of
CCPPAATTHH is ":/special/include", that has the same
effect as --II.. --II//ssppeecciiaall//iinncclluuddee.
-
DDEEPPEENNDDEENNCCIIEESS__OOUUTTPPUUTT
If this variable is set, its value specifies how to output
-
dependencies for Make based on the non-system header files processed
by the compiler. System header files are ignored in the dependency
output.
The value of DDEEPPEENNDDEENNCCIIEESS__OOUUTTPPUUTT can be just a file name, in
which case the Make rules are written to that file, guessing the target
name from the source file name. Or the value can have the form
_f_i_l_e _t_a_r_g_e_t, in which case the rules are written to
file _f_i_l_e using _t_a_r_g_e_t as the target name.
In other words, this environment variable is equivalent to combining
the options --MMMM and --MMFF,
with an optional --MMTT switch too.
-
SSUUNNPPRROO__DDEEPPEENNDDEENNCCIIEESS
This variable is the same as DDEEPPEENNDDEENNCCIIEESS__OOUUTTPPUUTT (see above),
-
except that system header files are not ignored, so it implies
--MM rather than --MMMM. However, the dependence on the
main input file is omitted.
BUGS
For instructions on reporting bugs, see
.
-
1.
On some systems, ggcccc --sshhaarreedd
-
needs to build supplementary stub code for constructors to work. On
multi-libbed systems, ggcccc --sshhaarreedd must select the correct support
libraries to link against. Failing to supply the correct flags may lead
to subtle defects. Supplying them in cases where they are not necessary
is innocuous.
SEE ALSO
_g_p_l(7), _g_f_d_l(7), _f_s_f_-_f_u_n_d_i_n_g(7),
_c_p_p(1), _g_c_o_v(1), _a_s(1), _l_d(1), _g_d_b(1), _a_d_b(1), _d_b_x(1), _s_d_b(1)
and the Info entries for _g_c_c, _c_p_p, _a_s,
_l_d, _b_i_n_u_t_i_l_s and _g_d_b.
AUTHOR
See the Info entry for ggcccc, or
,
for contributors to GCC.
COPYRIGHT
Copyright (c) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997,
1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "GNU General Public License" and "Funding
Free Software", the Front-Cover texts being (a) (see below), and with
the Back-Cover Texts being (b) (see below). A copy of the license is
included in the _g_f_d_l(7) man page.
(a) The FSF's Front-Cover Text is:
A GNU Manual
(b) The FSF's Back-Cover Text is:
You have freedom to copy and modify this GNU Manual, like GNU
software. Copies published by the Free Software Foundation raise
funds for GNU development.