UNIFDEF(1)						    BSD General Commands Manual 						UNIFDEF(1)

NAME

     unifdef, unifdefall -- remove preprocessor conditionals from code

SYNOPSIS

     unifdef [-ceklst] [-Ipath] [-Dsym[=val]] [-Usym] [-iDsym[=val]] [-iUsym] ... [-o output] [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 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.

     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 pos-
	     sible, 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.
     -o output
	     The argument given is the name of an output file to be used instead of the standard output.  This file can be the same as the input
	     file.
     -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] 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 FreeBSD 4.7.

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.

BSD
								   June 5, 2009 							       BSD