The
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
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
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
-s
and
cpp -dM
to get lists of all the controlling symbols
and their definitions (or lack thereof),
then invokes
with appropriate arguments to process the file.
Available options:
-D sym [= val
]
Specify that a symbol is defined,
and optionally specify what value to give it
for the purpose of handling
#if
and
#elif
directives.
-U sym
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
is complemented,
i.e., the lines that would have been removed or blanked
are retained and vice versa.
-d
Turn on printing of degugging messages.
-e
Because
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
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.
-n
Add
#line
directives to the output following any deleted lines,
so that errors produced when compiling the output file correspond to
line numbers in the input file.
-s
Instead of processing the input file as usual,
this option causes
to produce a list of symbols that appear in expressions
that
understands.
It is useful in conjunction with the
-dM
option of
cpp(1)
for creating
command lines.
-t
Disables parsing for C comments
and line continuations,
which is useful
for plain text.
-iD sym [= val
]
-iU sym
Ignore
#ifdef s
If your C code uses
#ifdef s
to delimit non-C lines,
such as comments
or code which is under construction,
then you must tell
which symbols are used for that purpose so that it will not try to parse
comments
and line continuations
inside those
#ifdef s
One specifies ignored symbols with
-iD sym [= val ]
and
-iU sym
similar to
-D sym [= val
]
and
-U sym
above.
-I path
Specifies to
unifdefall
an additional place to look for
#include
files.
This option is ignored by
for compatibility with
cpp(1)
and to simplify the implementation of
unifdefall
The
utility copies its output to
stdout
and will take its input from
stdin
if no
file
argument is given.
The
utility works nicely with the
-D sym
option of
diff(1).
EXIT STATUS
The
utility exits 0 if the output is an exact copy of the input,
1 if not, and 2 if in trouble.
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 )
