NAME    [Toc]    [Back]

     unifdef - remove preprocessor conditionals from code

SYNOPSIS    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

     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.

     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  behavior
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] and -iUsym similar to -Dsym [=val] and  -Usym
above.

     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    [Toc]    [Back]

     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    [Toc]    [Back]

     cpp(1), diff(1)

HISTORY    [Toc]    [Back]

     The unifdef command appeared in 4.3BSD.

BUGS    [Toc]    [Back]

     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 doesn't correspond to
modern
     cpp(1) behaviour.

OpenBSD      3.6                       September     24,     2002