unifdef - remove preprocessor conditionals from code
unifdef [-ceklst] [-Ipath -Dsym [=val] -Usym -iDsym [=val]
The unifdef utility selectively processes conditional cpp(1)
It removes from a file both the directives and any additional text that
they specify should be removed, while otherwise leaving the
The unifdef utility acts on #if, #ifdef, #ifndef, #elif,
#endif lines, and it understands only the commonly-used subset of the expression
syntax for #if and #elif lines. It handles integer
symbols defined on the command line, the defined() operator
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
and #ifndef directives if the symbol is specified on the
otherwise they are also passed through unchanged. By default, it ignores
#if and #elif lines with constant expressions, or they may
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
directives and knows when the layout is too odd to handle.
-Dsym [=val] Specify that a symbol is defined, and optionally specify
what value to give it for the purpose of handling
#if and #elif
-Usym Specify that a symbol is undefined. If the same
in more than one argument, the last occurrence dominates.
-c If the -c flag is specified, then the operation of
complemented, i.e., the lines that would have been
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
hanging off its right hand end. By default, if
to process such a directive, it will complain that
the line is
too obfuscated. The -e option changes the behavior
where possible, such lines are left unprocessed instead of reporting
-k Process #if and #elif lines with constant expressions. By default,
sections controlled by such lines are passed
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
-s Instead of processing the input file as usual, this
unifdef to produce a list of symbols that appear in
that unifdef understands. It is useful in conjunction with the
-dM option of cpp(1) for creating unifdef command
-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
[=val] and -iUsym similar to -Dsym [=val] and -Usym
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
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.
The unifdef command appeared in 4.3BSD.
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
Trigraphs are not recognized.
There is no support for symbols with different definitions
points in the source file.
The text-mode and ignore functionality doesn't correspond to
OpenBSD 3.6 September 24, 2002
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