path: root/usr.bin/unifdef/unifdef.1

.\"	$OpenBSD: unifdef.1,v 1.16 2007/05/31 19:20:19 jmc Exp $
.\" Copyright (c) 1985, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Dave Yost. Support for #if and #elif was added by Tony Finch.
.\"
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.\"     @(#)unifdef.1	8.2 (Berkeley) 4/1/94
.\"	$dotat: things/unifdef.1,v 1.26 2002/09/24 19:44:12 fanf2 Exp $
.\" $FreeBSD: src/usr.bin/unifdef/unifdef.1,v 1.15 2002/09/24 19:48:39 fanf Exp $
.\"
.Dd $Mdocdate: May 31 2007 $
.Dt UNIFDEF 1
.Os
.Sh NAME
.Nm unifdef
.Nd remove preprocessor conditionals from code
.Sh SYNOPSIS
.Nm
.Op Fl ceklst
.Sm off
.Oo
.Fl D Ar sym
.Op = Ar val
.Oc
.Op Fl I Ar path
.Oo
.Fl iD Ar sym
.Op = Ar val
.Oc
.Op Fl iU Ar sym
.Op Fl U Ar sym
.Sm on
.Op Ar file
.Sh DESCRIPTION
The
.Nm
utility selectively processes conditional
.Xr 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.
.Pp
The
.Nm
utility acts on
.Ic #if , #ifdef , #ifndef ,
.Ic #elif , #else ,
and
.Ic #endif
lines,
and it understands only the commonly-used subset
of the expression syntax for
.Ic #if
and
.Ic #elif
lines.
It handles
integer values of symbols defined on the command line,
the
.Fn defined
operator applied to symbols defined or undefined on the command line,
the operators
.Ic \&! , < , > , <= ,
.Ic >= , == , != , && ,
.Ic || ,
and parenthesized expressions.
Anything that it does not understand is passed through unharmed.
It only processes
.Ic #ifdef
and
.Ic #ifndef
directives if the symbol is specified on the command line,
otherwise they are also passed through unchanged.
By default, it ignores
.Ic #if
and
.Ic #elif
lines with constant expressions,
or they may be processed by specifying the
.Fl k
flag on the command line.
.Pp
The
.Nm
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.
.Pp
The options are as follows:
.Pp
.Bl -tag -width indent -compact
.It Fl c
If the
.Fl c
flag is specified,
then the operation of
.Nm
is complemented,
i.e., the lines that would have been removed or blanked
are retained and vice versa.
.Pp
.Sm off
.It Xo
.Fl D Ar sym
.Op = Ar val
.Xc
.Sm on
Specify that a symbol is defined,
and optionally specify what value to give it
for the purpose of handling
.Ic #if
and
.Ic #elif
directives.
.Pp
.It Fl e
Because
.Nm
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
.Nm
has to process such a directive,
it will complain that the line is too obfuscated.
The
.Fl e
option changes the behavior so that,
where possible,
such lines are left unprocessed instead of reporting an error.
.Pp
.Sm off
.It Xo
.Fl iD Ar sym
.Op = Ar val
.Xc
.Sm on
.It Fl iU Ns Ar sym
Ignore
.Ic #ifdef Ns s .
If your C code uses
.Ic #ifdef Ns s
to delimit non-C lines,
such as comments
or code which is under construction,
then you must tell
.Nm
which symbols are used for that purpose so that it will not try to parse
comments and line continuations
inside those
.Ic #ifdef Ns s .
One specifies ignored symbols with
.Sm off
.Fl iD Ar sym Op = Ar val
.Sm on
and
.Fl iU Ns Ar sym ,
similar to
.Sm off
.Fl D Ar sym Op = Ar val
.Sm on
and
.Fl U Ns Ar sym .
.Pp
.It Fl k
Process
.Ic #if
and
.Ic #elif
lines with constant expressions.
By default, sections controlled by such lines are passed through unchanged
because they typically start
.Li #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.
.Pp
.It Fl l
Replace removed lines with blank lines
instead of deleting them.
.Pp
.It Fl s
Instead of processing the input file as usual,
this option causes
.Nm
to produce a list of symbols that appear in expressions
that
.Nm
understands.
It is useful in conjunction with the
.Fl dM
option of
.Xr cpp 1
for creating
.Nm
command lines.
.Pp
.It Fl t
Disables parsing for C comments
and line continuations,
which is useful
for plain text.
.Pp
.It Fl U Ns Ar sym
Specify that a symbol is undefined.
If the same symbol appears in more than one argument,
the last occurrence dominates.
.Pp
.El
.Pp
The
.Nm
utility copies its output to
.Em stdout
and will take its input from
.Em stdin
if no
.Ar file
argument is given.
.Pp
The
.Nm
utility works nicely with the
.Fl D Ns Ar sym
option of
.Xr diff 1 .
.Sh DIAGNOSTICS
.Bl -item
.It
Too many levels of nesting.
.It
Inappropriate
.Ic #elif ,
.Ic #else
or
.Ic #endif .
.It
Obfuscated preprocessor control line.
.It
Premature
.Tn EOF
(with the line number of the most recent unterminated
.Ic #if ) .
.It
.Tn EOF
in comment.
.El
.Pp
The
.Nm
utility exits 0 if the output is an exact copy of the input,
1 if not, and 2 if in trouble.
.Sh SEE ALSO
.Xr cpp 1 ,
.Xr diff 1
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.3 .
.Sh BUGS
Expression evaluation is very limited.
.Pp
Preprocessor control lines split across more than one physical line
(because of comments or backslash-newline)
cannot be handled in every situation.
.Pp
Trigraphs are not recognized.
.Pp
There is no support for symbols with different definitions at
different points in the source file.
.Pp
The text-mode and ignore functionality doesn't correspond to modern
.Xr cpp 1
behaviour.