UNIFDEF(1) Programmer's Manual UNIFDEF(1)
NAME
unifdef, unifdefall — remove preprocessor conditionals from code
SYNOPSIS
unifdef [-bBcdehKkmnsStV] [-Ipath] [-[i]Dsym[=val]] [-[i]Usym] ...
[-f defile] [-x {012}] [-M backext] [-o outfile] [infile ...]
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, using macros specified in -D and -U command line options or
in -f definitions files. A directive is processed if the macro specifi-
cations are sufficient to provide a definite value for its control ex-
pression. 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 #ifdef or #ifndef directive is passed through unchanged
if its controlling macro is not specified. Any #if or #elif control ex-
pression that has an unknown value or that unifdef cannot parse is passed
through unchanged. By default, unifdef ignores #if and #elif lines with
constant expressions; it can be told to process them by specifying the -k
flag on the command line.
It understands a commonly-used subset of the expression syntax for #if
and #elif lines: integer constants, integer values of macros defined on
the command line, the defined() operator, the operators !, <, >, <=, >=,
==, !=, &&, ||, and parenthesized expressions. A kind of “short circuit”
evaluation is used for the && 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 || is definitely true then the
result is true.
When evaluating an expression, unifdef does not expand macros first. The
value of a macro must be a simple number, not an expression. A limited
form of indirection is allowed, where one macro's value is the name of
another.
In most cases, unifdef does not distinguish between object-like macros
(without arguments) and function-like macros (with arguments). A func-
tion-like macro invocation can appear in #if and #elif control expres-
sions. If the macro is not explicitly defined, or is defined with the -D
flag on the command-line, or with #define in a -f definitions file, its
arguments are ignored. If a macro is explicitly undefined on the command
line with the -U flag, or with #undef in a -f definitions file, it may
not have any arguments since this leads to a syntax error.
The unifdef 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.
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 macros and their definitions (or lack thereof), then
invokes unifdef with appropriate arguments to process the file.
OPTIONS
-Dsym=val
Specify that a macro is defined to a given value.
-Dsym Specify that a macro is defined to the value 1.
-Usym Specify that a macro is undefined.
If the same macro appears in more than one argument, the last oc-
currence dominates.
-iDsym[=val]
-iUsym C strings, comments, and line continuations are ignored within
#ifdef and #ifndef blocks controlled by macros specified with
these options.
-f defile
The file defile contains #define and #undef preprocessor direc-
tives, which have the same effect as the corresponding -D and -U
command-line arguments. You can have multiple -f arguments and
mix them with -D and -U arguments; later options override earlier
ones.
Each directive must be on a single line. Object-like macro defi-
nitions (without arguments) are set to the given value. Func-
tion-like macro definitions (with arguments) are treated as if
they are set to 1.
-b Replace removed lines with blank lines instead of deleting them.
Mutually exclusive with the -B option.
-B Compress blank lines around a deleted section. Mutually exclu-
sive with the -b option.
-c Complement, i.e., lines that would have been removed or blanked
are retained and vice versa.
-d Turn on printing of debugging messages.
-e By default, unifdef will report an error if it needs to remove a
preprocessor directive that spans more than one line, for exam-
ple, if it has a multi-line comment hanging off its right hand
end. The -e flag makes it ignore the line instead.
-h Print help.
-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.
-K Always treat the result of && and || operators as unknown if ei-
ther operand is unknown, instead of short-circuiting when unknown
operands can't affect the result. This option is for compatibil-
ity with older versions of unifdef.
-k Process #if and #elif lines with constant expressions. By de-
fault, sections controlled by such lines are passed through un-
changed 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.
-m Modify one or more input files in place.
-M backext
Modify input files in place, and keep backups of the original
files by appending the backext to the input filenames.
-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.
-o outfile
Write output to the file outfile instead of the standard output
when processing a single file.
-s Instead of processing an input file as usual, this option causes
unifdef to produce a list of macros that are used in preprocessor
directive controlling expressions.
-S Like the -s option, but the nesting depth of each macro is also
printed. This is useful for working out the number of possible
combinations of interdependent defined/undefined macros.
-t Disables parsing for C strings, comments, and line continuations,
which is useful for plain text. This is a blanket version of the
-iD and -iU flags.
-V Print version details.
-x {012}
Set exit status mode to zero, one, or two. See the EXIT STATUS
section below for details.
The unifdef utility takes its input from stdin if there are no file argu-
ments. You must use the -m or -M options if there are multiple input
files. You can specify inut from stdin or output to stdout with ‘-’.
The unifdef utility works nicely with the -Dsym option of diff(1).
EXIT STATUS
In normal usage the unifdef utility's exit status depends on the mode set
using the -x option.
If the exit mode is zero (the default) then unifdef exits with status 0
if the output is an exact copy of the input, or with status 1 if the out-
put differs.
If the exit mode is one, unifdef exits with status 1 if the output is un-
modified or 0 if it differs.
If the exit mode is two, unifdef exits with status zero in both cases.
In all exit modes, unifdef exits with status 2 if there is an error.
The exit status is 0 if the -h or -V command line options are given.
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.
SEE ALSO
cpp(1), diff(1)
The unifdef home page is http://dotat.at/prog/unifdef
HISTORY
The unifdef command appeared in 2.9BSD. ANSI C support was added in
FreeBSD 4.7.
AUTHORS
The original implementation was written by Dave Yost <Dave@Yost.com>.
Tony Finch <dot@dotat.at> rewrote it to support ANSI C.
BUGS
Expression evaluation is very limited.
Handling one line at a time means preprocessor directives 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 macros with different definitions at different
points in the source file.
The text-mode and ignore functionality does not correspond to modern
cpp(1) behaviour.
January 7, 2014
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