unifdef, unifdefall -- remove preprocessor conditionals from code
unifdef [-ceklst] [-Ipath -Dsym[=val] -Usym -iDsym[=val] -iUsym] ...
unifdefall [-Ipath] ... file
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 unifdef -s 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.
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
-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.
-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] 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).
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.
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
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
The unifdef command appeared in 4.3BSD. ANSI C support was added in
FreeBSD 5.2.1 September 24, 2002 FreeBSD 5.2.1 [ Back ]