NAME
unifdef,
unifdefall
- remove preprocessor conditionals from code
SYNOPSIS
unifdef
[-ceklst]
[-Ipath]
[-Dsym[=val]]
[-Usym]
[-iDsym[=val]]
[-iUsym]
...
[file]
unifdefall
[-Ipath]
...
file
DESCRIPTION
The
unifdef
utility selectively processes conditional
cpp(1)
directives.
It removes from a file both the directives and any additional text
that they specify should be removed, while otherwise leaving the
file alone.
The
unifdef
utility acts on
#if, #ifdef, #ifndef, #elif, #else,
and
#endif
lines,
and it understands only the commonly-used subset
of the expression syntax for
#if
and
#elif
lines.
It handles
integer values of symbols defined on the command line,
the
defined(
)
operator applied to symbols defined or undefined on the command line,
the operators
!, <, >, <=, >=, ==, !=, &&, ||,
and parenthesized expressions.
Anything that it does not understand is passed through unharmed.
It only processes
#ifdef
and
#ifndef
directives if the symbol is specified on the command line,
otherwise they are also passed through unchanged.
By default, it ignores
#if
and
#elif
lines with constant expressions,
or they may be processed by specifying the
-k
flag on the command line.
The
unifdef
utility also understands just enough about C
to know when one of the directives is inactive
because it is inside
a comment,
or affected by a backslash-continued line.
It spots unusually-formatted preprocessor directives
and knows when the layout is too odd to handle.
A script called
unifdefall
can be used to remove all conditional
cpp(1)
directives from a file.
It uses
Fls
and
cpp-dM
to get lists of all the controlling symbols
and their definitions (or lack thereof),
then invokes
unifdef
with appropriate arguments to process the file.
Available options:
- -Dsym[=val]
-
Specify that a symbol is defined,
and optionally specify what value to give it
for the purpose of handling
#if
and
#elif
directives.
- -Usym
-
Specify that a symbol is undefined.
If the same symbol appears in more than one argument,
the last occurrence dominates.
- -c
-
If the
-c
flag is specified,
then the operation of
unifdef
is complemented,
i.e., the lines that would have been removed or blanked
are retained and vice versa.
- -e
-
Because
unifdef
processes its input one line at a time,
it cannot remove preprocessor directives that span more than one line.
The most common example of this is a directive with a multi-line
comment hanging off its right hand end.
By default,
if
unifdef
has to process such a directive,
it will complain that the line is too obfuscated.
The
-e
option changes the behaviour so that,
where possible,
such lines are left unprocessed instead of reporting an error.
- -k
-
Process
#if
and
#elif
lines with constant expressions.
By default, sections controlled by such lines are passed through unchanged
because they typically start
``
#if 0
''
and are used as a kind of comment to sketch out future or past development.
It would be rude to strip them out, just as it would be for normal comments.
- -l
-
Replace removed lines with blank lines
instead of deleting them.
- -s
-
Instead of processing the input file as usual,
this option causes
unifdef
to produce a list of symbols that appear in expressions
that
unifdef
understands.
It is useful in conjunction with the
-dM
option of
cpp(1)
for creating
unifdef
command lines.
- -t
-
Disables parsing for C comments
and line continuations,
which is useful
for plain text.
- -iDsym[=val]
-
- -iUsym
-
Ignore
#ifdefs.
If your C code uses
#ifdefs
to delimit non-C lines,
such as comments
or code which is under construction,
then you must tell
unifdef
which symbols are used for that purpose so that it will not try to parse
comments
and line continuations
inside those
#ifdefs.
One specifies ignored symbols with
-iDsym=val[.blm Pp]
and
-iUsym
similar to
-Dsym[=val]
and
-Usym
above.
- -Ipath
-
Specifies to
unifdefall
an additional place to look for
#include
files.
This option is ignored by
unifdef
for compatibility with
cpp(1)
and to simplify the implementation of
unifdefall.
The
unifdef
utility copies its output to
stdout
and will take its input from
stdin
if no
file
argument is given.
The
unifdef
utility works nicely with the
-Dsym
option of
diff(1).
DIAGNOSTICS
-
Too many levels of nesting.
-
Inappropriate
#elif,
#else
or
#endif.
-
Obfuscated preprocessor control line.
-
Premature
EOF
(with the line number of the most recent unterminated
#if).
-
EOF
in comment.
The
unifdef
utility exits 0 if the output is an exact copy of the input,
1 if not, and 2 if in trouble.
SEE ALSO
cpp(1),
diff(1)
HISTORY
The
unifdef
command appeared in
4.3BSD.
ANSI C
support was added in
FreeBSD4.7.
BUGS
Expression evaluation is very limited.
Preprocessor control lines split across more than one physical line
(because of comments or backslash-newline)
cannot be handled in every situation.
Trigraphs are not recognized.
There is no support for symbols with different definitions at
different points in the source file.
The text-mode and ignore functionality does not correspond to modern
cpp(1)
behaviour.