unifdef.1

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.\" Dave Yost. It was rewritten to support ANSI C by Tony Finch.
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.Dd January 18, 2011
.Dt UNIFDEF 1 PRM
.Os " "
.Sh NAME
.Nm unifdef , unifdefall
.Nd remove preprocessor conditionals from code
.Sh SYNOPSIS
.Nm
.Op Fl bBcdeKknsStV
.Op Fl I Ns Ar path
.Op Fl D Ns Ar sym Ns Op = Ns Ar val
.Op Fl U Ns Ar sym
.Op Fl iD Ns Ar sym Ns Op = Ns Ar val
.Op Fl iU Ns Ar sym
.Ar ...
.Op Fl o Ar outfile
.Op Ar infile
.Nm unifdefall
.Op Fl I Ns Ar path
.Ar ...
.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 , #elif , #else ,
and
.Ic #endif
lines.
A directive is only processed
if the symbols specified on the command line are sufficient to allow
.Nm
to get a definite value for its control expression.
If the result is false,
the directive and the following lines under its control are removed.
If the result is true,
only the directive is removed.
An
.Ic #ifdef
or
.Ic #ifndef
directive is passed through unchanged
if its controlling symbol is not specified on the command line.
Any
.Ic #if
or
.Ic #elif
control expression that has an unknown value or that
.Nm
cannot parse is passed through unchanged.
By default,
.Nm
ignores
.Ic #if
and
.Ic #elif
lines with constant expressions;
it can be told to process them by specifying the
.Fl k
flag on the command line.
.Pp
It understands a commonly-used subset
of the expression syntax for
.Ic #if
and
.Ic #elif
lines:
integer constants,
integer values of symbols defined on the command line,
the
.Fn defined
operator,
the operators
.Ic \&! , < , > , <= , >= , == , != , && , || ,
and parenthesized expressions.
A kind of
.Dq "short circuit"
evaluation is used for the
.Ic &&
operator:
if either operand is definitely false then the result is false,
even if the value of the other operand is unknown.
Similarly,
if either operand of
.Ic ||
is definitely true then the result is true.
.Pp
In most cases, the
.Nm
utility does not distinguish between object-like macros
(without arguments) and function-like arguments (with arguments).
If a macro is not explicitly defined, or is defined with the
.Fl D
flag on the command-line, its arguments are ignored.
If a macro is explicitly undefined on the command line with the
.Fl U
flag, it may not have any arguments since this leads to a syntax error.
.Pp
The
.Nm
utility 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 for it to handle.
.Pp
A script called
.Nm unifdefall
can be used to remove all conditional
.Xr cpp 1
directives from a file.
It uses
.Nm Fl s
and
.Nm cpp Fl dM
to get lists of all the controlling symbols
and their definitions (or lack thereof),
then invokes
.Nm
with appropriate arguments to process the file.
.Sh OPTIONS
.Pp
.Bl -tag -width indent -compact
.It Fl D Ns Ar sym Ns = Ns Ar val
Specify that a symbol is defined to a given value
which is used when evaluating
.Ic #if
and
.Ic #elif
control expressions.
.Pp
.It Fl D Ns Ar sym
Specify that a symbol is defined to the value 1.
.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
.It Fl b
Replace removed lines with blank lines
instead of deleting them.
Mutually exclusive with the
.Fl B
option.
.Pp
.It Fl B
Compress blank lines around a deleted section.
Mutually exclusive with the
.Fl b
option.
.Pp
.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
.It Fl d
Turn on printing of debugging messages.
.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 behaviour so that,
where possible,
such lines are left unprocessed instead of reporting an error.
.Pp
.It Fl K
Always treat the result of
.Ic &&
and
.Ic ||
operators as unknown if either operand is unknown,
instead of short-circuiting when unknown operands can't affect the result.
This option is for compatibility with older versions of
.Nm .
.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
.Dq 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 n
Add
.Li #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.
.Pp
.It Fl o Ar outfile
Write output to the file
.Ar outfile
instead of the standard output.
If
.Ar outfile
is the same as the input file,
the output is written to a temporary file
which is renamed into place when
.Nm
completes successfully.
.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 S
Like the
.Fl s
option, but the nesting depth of each symbol is also printed.
This is useful for working out the number of possible combinations
of interdependent defined/undefined symbols.
.Pp
.It Fl t
Disables parsing for C comments
and line continuations,
which is useful
for plain text.
.Pp
.It Fl iD Ns Ar sym Ns Op = Ns Ar val
.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 .
You can specify ignored symbols with
.Fl iD Ns Ar sym Ns Oo = Ns Ar val Oc
and
.Fl iU Ns Ar sym
similar to
.Fl D Ns Ar sym Ns Op = Ns Ar val
and
.Fl U Ns Ar sym
above.
.Pp
.It Fl I Ns Ar path
Specifies to
.Nm unifdefall
an additional place to look for
.Ic #include
files.
This option is ignored by
.Nm
for compatibility with
.Xr cpp 1
and to simplify the implementation of
.Nm unifdefall .
.Pp
.It Fl V
Print version details.
.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 EXIT STATUS
The
.Nm
utility exits 0 if the output is an exact copy of the input,
1 if not, and 2 if in trouble.
.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
.Sh SEE ALSO
.Xr cpp 1 ,
.Xr diff 1
.Sh HISTORY
The
.Nm
command appeared in
.Bx 2.9 .
.Tn ANSI\~C
support was added in
.Fx 4.7 .
.Sh AUTHORS
The original implementation was written by
.An Dave Yost Aq Dave@Yost.com .
.An Tony Finch Aq dot@dotat.at
rewrote it to support
.Tn ANSI\~C .
.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 does not correspond to modern
.Xr cpp 1
behaviour.