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.rm #[ #] #H #V #F C
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.\" ========================================================================
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.\"
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.IX Title "CPP 1"
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.TH CPP 1 "2007-10-07" "gcc-4.2.2" "GNU"
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.SH "NAME"
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cpp \- The C Preprocessor
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.SH "SYNOPSIS"
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.IX Header "SYNOPSIS"
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cpp [\fB\-D\fR\fImacro\fR[=\fIdefn\fR]...] [\fB\-U\fR\fImacro\fR]
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    [\fB\-I\fR\fIdir\fR...] [\fB\-iquote\fR\fIdir\fR...]
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    [\fB\-W\fR\fIwarn\fR...]
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    [\fB\-M\fR|\fB\-MM\fR] [\fB\-MG\fR] [\fB\-MF\fR \fIfilename\fR]
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    [\fB\-MP\fR] [\fB\-MQ\fR \fItarget\fR...]
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    [\fB\-MT\fR \fItarget\fR...]
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    [\fB\-P\fR] [\fB\-fno\-working\-directory\fR]
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    [\fB\-x\fR \fIlanguage\fR] [\fB\-std=\fR\fIstandard\fR]
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    \fIinfile\fR \fIoutfile\fR
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.PP
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Only the most useful options are listed here; see below for the remainder.
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.SH "DESCRIPTION"
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.IX Header "DESCRIPTION"
150
The C preprocessor, often known as \fIcpp\fR, is a \fImacro processor\fR
151
that is used automatically by the C compiler to transform your program
152
before compilation.  It is called a macro processor because it allows
153
you to define \fImacros\fR, which are brief abbreviations for longer
154
constructs.
155
.PP
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The C preprocessor is intended to be used only with C, \*(C+, and
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Objective-C source code.  In the past, it has been abused as a general
158
text processor.  It will choke on input which does not obey C's lexical
159
rules.  For example, apostrophes will be interpreted as the beginning of
160
character constants, and cause errors.  Also, you cannot rely on it
161
preserving characteristics of the input which are not significant to
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C\-family languages.  If a Makefile is preprocessed, all the hard tabs
163
will be removed, and the Makefile will not work.
164
.PP
165
Having said that, you can often get away with using cpp on things which
166
are not C.  Other Algol-ish programming languages are often safe
167
(Pascal, Ada, etc.) So is assembly, with caution.  \fB\-traditional\-cpp\fR
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mode preserves more white space, and is otherwise more permissive.  Many
169
of the problems can be avoided by writing C or \*(C+ style comments
170
instead of native language comments, and keeping macros simple.
171
.PP
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Wherever possible, you should use a preprocessor geared to the language
173
you are writing in.  Modern versions of the \s-1GNU\s0 assembler have macro
174
facilities.  Most high level programming languages have their own
175
conditional compilation and inclusion mechanism.  If all else fails,
176
try a true general text processor, such as \s-1GNU\s0 M4.
177
.PP
178
C preprocessors vary in some details.  This manual discusses the \s-1GNU\s0 C
179
preprocessor, which provides a small superset of the features of \s-1ISO\s0
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Standard C.  In its default mode, the \s-1GNU\s0 C preprocessor does not do a
181
few things required by the standard.  These are features which are
182
rarely, if ever, used, and may cause surprising changes to the meaning
183
of a program which does not expect them.  To get strict \s-1ISO\s0 Standard C,
184
you should use the \fB\-std=c89\fR or \fB\-std=c99\fR options, depending
185
on which version of the standard you want.  To get all the mandatory
186
diagnostics, you must also use \fB\-pedantic\fR.
187
.PP
188
This manual describes the behavior of the \s-1ISO\s0 preprocessor.  To
189
minimize gratuitous differences, where the \s-1ISO\s0 preprocessor's
190
behavior does not conflict with traditional semantics, the
191
traditional preprocessor should behave the same way.  The various
192
differences that do exist are detailed in the section \fBTraditional
193
Mode\fR.
194
.PP
195
For clarity, unless noted otherwise, references to \fB\s-1CPP\s0\fR in this
196
manual refer to \s-1GNU\s0 \s-1CPP\s0.
197
.SH "OPTIONS"
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.IX Header "OPTIONS"
199
The C preprocessor expects two file names as arguments, \fIinfile\fR and
200
\&\fIoutfile\fR.  The preprocessor reads \fIinfile\fR together with any
201
other files it specifies with \fB#include\fR.  All the output generated
202
by the combined input files is written in \fIoutfile\fR.
203
.PP
204
Either \fIinfile\fR or \fIoutfile\fR may be \fB\-\fR, which as
205
\&\fIinfile\fR means to read from standard input and as \fIoutfile\fR
206
means to write to standard output.  Also, if either file is omitted, it
207
means the same as if \fB\-\fR had been specified for that file.
208
.PP
209
Unless otherwise noted, or the option ends in \fB=\fR, all options
210
which take an argument may have that argument appear either immediately
211
after the option, or with a space between option and argument:
212
\&\fB\-Ifoo\fR and \fB\-I foo\fR have the same effect.
213
.PP
214
Many options have multi-letter names; therefore multiple single-letter
215
options may \fInot\fR be grouped: \fB\-dM\fR is very different from
216
\&\fB\-d\ \-M\fR.
217
.IP "\fB\-D\fR \fIname\fR" 4
218
.IX Item "-D name"
219
Predefine \fIname\fR as a macro, with definition \f(CW1\fR.
220
.IP "\fB\-D\fR \fIname\fR\fB=\fR\fIdefinition\fR" 4
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.IX Item "-D name=definition"
222
The contents of \fIdefinition\fR are tokenized and processed as if
223
they appeared during translation phase three in a \fB#define\fR
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directive.  In particular, the definition will be truncated by
225
embedded newline characters.
226
.Sp
227
If you are invoking the preprocessor from a shell or shell-like
228
program you may need to use the shell's quoting syntax to protect
229
characters such as spaces that have a meaning in the shell syntax.
230
.Sp
231
If you wish to define a function-like macro on the command line, write
232
its argument list with surrounding parentheses before the equals sign
233
(if any).  Parentheses are meaningful to most shells, so you will need
234
to quote the option.  With \fBsh\fR and \fBcsh\fR,
235
\&\fB\-D'\fR\fIname\fR\fB(\fR\fIargs...\fR\fB)=\fR\fIdefinition\fR\fB'\fR works.
236
.Sp
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\&\fB\-D\fR and \fB\-U\fR options are processed in the order they
238
are given on the command line.  All \fB\-imacros\fR \fIfile\fR and
239
\&\fB\-include\fR \fIfile\fR options are processed after all
240
\&\fB\-D\fR and \fB\-U\fR options.
241
.IP "\fB\-U\fR \fIname\fR" 4
242
.IX Item "-U name"
243
Cancel any previous definition of \fIname\fR, either built in or
244
provided with a \fB\-D\fR option.
245
.IP "\fB\-undef\fR" 4
246
.IX Item "-undef"
247
Do not predefine any system-specific or GCC-specific macros.  The
248
standard predefined macros remain defined.
249
.IP "\fB\-I\fR \fIdir\fR" 4
250
.IX Item "-I dir"
251
Add the directory \fIdir\fR to the list of directories to be searched
252
for header files.
253
.Sp
254
Directories named by \fB\-I\fR are searched before the standard
255
system include directories.  If the directory \fIdir\fR is a standard
256
system include directory, the option is ignored to ensure that the
257
default search order for system directories and the special treatment
258
of system headers are not defeated
259
\&.
260
.IP "\fB\-o\fR \fIfile\fR" 4
261
.IX Item "-o file"
262
Write output to \fIfile\fR.  This is the same as specifying \fIfile\fR
263
as the second non-option argument to \fBcpp\fR.  \fBgcc\fR has a
264
different interpretation of a second non-option argument, so you must
265
use \fB\-o\fR to specify the output file.
266
.IP "\fB\-Wall\fR" 4
267
.IX Item "-Wall"
268
Turns on all optional warnings which are desirable for normal code.
269
At present this is \fB\-Wcomment\fR, \fB\-Wtrigraphs\fR,
270
\&\fB\-Wmultichar\fR and a warning about integer promotion causing a
271
change of sign in \f(CW\*(C`#if\*(C'\fR expressions.  Note that many of the
272
preprocessor's warnings are on by default and have no options to
273
control them.
274
.IP "\fB\-Wcomment\fR" 4
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.IX Item "-Wcomment"
276
.PD 0
277
.IP "\fB\-Wcomments\fR" 4
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.IX Item "-Wcomments"
279
.PD
280
Warn whenever a comment-start sequence \fB/*\fR appears in a \fB/*\fR
281
comment, or whenever a backslash-newline appears in a \fB//\fR comment.
282
(Both forms have the same effect.)
283
.IP "\fB\-Wtrigraphs\fR" 4
284
.IX Item "-Wtrigraphs"
285
Most trigraphs in comments cannot affect the meaning of the program.
286
However, a trigraph that would form an escaped newline (\fB??/\fR at
287
the end of a line) can, by changing where the comment begins or ends.
288
Therefore, only trigraphs that would form escaped newlines produce
289
warnings inside a comment.
290
.Sp
291
This option is implied by \fB\-Wall\fR.  If \fB\-Wall\fR is not
292
given, this option is still enabled unless trigraphs are enabled.  To
293
get trigraph conversion without warnings, but get the other
294
\&\fB\-Wall\fR warnings, use \fB\-trigraphs \-Wall \-Wno\-trigraphs\fR.
295
.IP "\fB\-Wtraditional\fR" 4
296
.IX Item "-Wtraditional"
297
Warn about certain constructs that behave differently in traditional and
298
\&\s-1ISO\s0 C.  Also warn about \s-1ISO\s0 C constructs that have no traditional C
299
equivalent, and problematic constructs which should be avoided.
300
.IP "\fB\-Wimport\fR" 4
301
.IX Item "-Wimport"
302
Warn the first time \fB#import\fR is used.
303
.IP "\fB\-Wundef\fR" 4
304
.IX Item "-Wundef"
305
Warn whenever an identifier which is not a macro is encountered in an
306
\&\fB#if\fR directive, outside of \fBdefined\fR.  Such identifiers are
307
replaced with zero.
308
.IP "\fB\-Wunused\-macros\fR" 4
309
.IX Item "-Wunused-macros"
310
Warn about macros defined in the main file that are unused.  A macro
311
is \fIused\fR if it is expanded or tested for existence at least once.
312
The preprocessor will also warn if the macro has not been used at the
313
time it is redefined or undefined.
314
.Sp
315
Built-in macros, macros defined on the command line, and macros
316
defined in include files are not warned about.
317
.Sp
318
\&\fINote:\fR If a macro is actually used, but only used in skipped
319
conditional blocks, then \s-1CPP\s0 will report it as unused.  To avoid the
320
warning in such a case, you might improve the scope of the macro's
321
definition by, for example, moving it into the first skipped block.
322
Alternatively, you could provide a dummy use with something like:
323
.Sp
324
.Vb 2
325
\&        #if defined the_macro_causing_the_warning
326
\&        #endif
327
.Ve
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.IP "\fB\-Wendif\-labels\fR" 4
329
.IX Item "-Wendif-labels"
330
Warn whenever an \fB#else\fR or an \fB#endif\fR are followed by text.
331
This usually happens in code of the form
332
.Sp
333
.Vb 5
334
\&        #if FOO
335
\&        ...
336
\&        #else FOO
337
\&        ...
338
\&        #endif FOO
339
.Ve
340
.Sp
341
The second and third \f(CW\*(C`FOO\*(C'\fR should be in comments, but often are not
342
in older programs.  This warning is on by default.
343
.IP "\fB\-Werror\fR" 4
344
.IX Item "-Werror"
345
Make all warnings into hard errors.  Source code which triggers warnings
346
will be rejected.
347
.IP "\fB\-Wsystem\-headers\fR" 4
348
.IX Item "-Wsystem-headers"
349
Issue warnings for code in system headers.  These are normally unhelpful
350
in finding bugs in your own code, therefore suppressed.  If you are
351
responsible for the system library, you may want to see them.
352
.IP "\fB\-w\fR" 4
353
.IX Item "-w"
354
Suppress all warnings, including those which \s-1GNU\s0 \s-1CPP\s0 issues by default.
355
.IP "\fB\-pedantic\fR" 4
356
.IX Item "-pedantic"
357
Issue all the mandatory diagnostics listed in the C standard.  Some of
358
them are left out by default, since they trigger frequently on harmless
359
code.
360
.IP "\fB\-pedantic\-errors\fR" 4
361
.IX Item "-pedantic-errors"
362
Issue all the mandatory diagnostics, and make all mandatory diagnostics
363
into errors.  This includes mandatory diagnostics that \s-1GCC\s0 issues
364
without \fB\-pedantic\fR but treats as warnings.
365
.IP "\fB\-M\fR" 4
366
.IX Item "-M"
367
Instead of outputting the result of preprocessing, output a rule
368
suitable for \fBmake\fR describing the dependencies of the main
369
source file.  The preprocessor outputs one \fBmake\fR rule containing
370
the object file name for that source file, a colon, and the names of all
371
the included files, including those coming from \fB\-include\fR or
372
\&\fB\-imacros\fR command line options.
373
.Sp
374
Unless specified explicitly (with \fB\-MT\fR or \fB\-MQ\fR), the
375
object file name consists of the basename of the source file with any
376
suffix replaced with object file suffix.  If there are many included
377
files then the rule is split into several lines using \fB\e\fR\-newline.
378
The rule has no commands.
379
.Sp
380
This option does not suppress the preprocessor's debug output, such as
381
\&\fB\-dM\fR.  To avoid mixing such debug output with the dependency
382
rules you should explicitly specify the dependency output file with
383
\&\fB\-MF\fR, or use an environment variable like
384
\&\fB\s-1DEPENDENCIES_OUTPUT\s0\fR.  Debug output
385
will still be sent to the regular output stream as normal.
386
.Sp
387
Passing \fB\-M\fR to the driver implies \fB\-E\fR, and suppresses
388
warnings with an implicit \fB\-w\fR.
389
.IP "\fB\-MM\fR" 4
390
.IX Item "-MM"
391
Like \fB\-M\fR but do not mention header files that are found in
392
system header directories, nor header files that are included,
393
directly or indirectly, from such a header.
394
.Sp
395
This implies that the choice of angle brackets or double quotes in an
396
\&\fB#include\fR directive does not in itself determine whether that
397
header will appear in \fB\-MM\fR dependency output.  This is a
398
slight change in semantics from \s-1GCC\s0 versions 3.0 and earlier.
399
.IP "\fB\-MF\fR \fIfile\fR" 4
400
.IX Item "-MF file"
401
When used with \fB\-M\fR or \fB\-MM\fR, specifies a
402
file to write the dependencies to.  If no \fB\-MF\fR switch is given
403
the preprocessor sends the rules to the same place it would have sent
404
preprocessed output.
405
.Sp
406
When used with the driver options \fB\-MD\fR or \fB\-MMD\fR,
407
\&\fB\-MF\fR overrides the default dependency output file.
408
.IP "\fB\-MG\fR" 4
409
.IX Item "-MG"
410
In conjunction with an option such as \fB\-M\fR requesting
411
dependency generation, \fB\-MG\fR assumes missing header files are
412
generated files and adds them to the dependency list without raising
413
an error.  The dependency filename is taken directly from the
414
\&\f(CW\*(C`#include\*(C'\fR directive without prepending any path.  \fB\-MG\fR
415
also suppresses preprocessed output, as a missing header file renders
416
this useless.
417
.Sp
418
This feature is used in automatic updating of makefiles.
419
.IP "\fB\-MP\fR" 4
420
.IX Item "-MP"
421
This option instructs \s-1CPP\s0 to add a phony target for each dependency
422
other than the main file, causing each to depend on nothing.  These
423
dummy rules work around errors \fBmake\fR gives if you remove header
424
files without updating the \fIMakefile\fR to match.
425
.Sp
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This is typical output:
427
.Sp
428
.Vb 1
429
\&        test.o: test.c test.h
430
.Ve
431
.Sp
432
.Vb 1
433
\&        test.h:
434
.Ve
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.IP "\fB\-MT\fR \fItarget\fR" 4
436
.IX Item "-MT target"
437
Change the target of the rule emitted by dependency generation.  By
438
default \s-1CPP\s0 takes the name of the main input file, including any path,
439
deletes any file suffix such as \fB.c\fR, and appends the platform's
440
usual object suffix.  The result is the target.
441
.Sp
442
An \fB\-MT\fR option will set the target to be exactly the string you
443
specify.  If you want multiple targets, you can specify them as a single
444
argument to \fB\-MT\fR, or use multiple \fB\-MT\fR options.
445
.Sp
446
For example, \fB\-MT\ '$(objpfx)foo.o'\fR might give
447
.Sp
448
.Vb 1
449
\&        $(objpfx)foo.o: foo.c
450
.Ve
451
.IP "\fB\-MQ\fR \fItarget\fR" 4
452
.IX Item "-MQ target"
453
Same as \fB\-MT\fR, but it quotes any characters which are special to
454
Make.  \fB\-MQ\ '$(objpfx)foo.o'\fR gives
455
.Sp
456
.Vb 1
457
\&        $$(objpfx)foo.o: foo.c
458
.Ve
459
.Sp
460
The default target is automatically quoted, as if it were given with
461
\&\fB\-MQ\fR.
462
.IP "\fB\-MD\fR" 4
463
.IX Item "-MD"
464
\&\fB\-MD\fR is equivalent to \fB\-M \-MF\fR \fIfile\fR, except that
465
\&\fB\-E\fR is not implied.  The driver determines \fIfile\fR based on
466
whether an \fB\-o\fR option is given.  If it is, the driver uses its
467
argument but with a suffix of \fI.d\fR, otherwise it take the
468
basename of the input file and applies a \fI.d\fR suffix.
469
.Sp
470
If \fB\-MD\fR is used in conjunction with \fB\-E\fR, any
471
\&\fB\-o\fR switch is understood to specify the dependency output file, but if used without \fB\-E\fR, each \fB\-o\fR
472
is understood to specify a target object file.
473
.Sp
474
Since \fB\-E\fR is not implied, \fB\-MD\fR can be used to generate
475
a dependency output file as a side-effect of the compilation process.
476
.IP "\fB\-MMD\fR" 4
477
.IX Item "-MMD"
478
Like \fB\-MD\fR except mention only user header files, not system
479
header files.
480
.IP "\fB\-x c\fR" 4
481
.IX Item "-x c"
482
.PD 0
483
.IP "\fB\-x c++\fR" 4
484
.IX Item "-x c++"
485
.IP "\fB\-x objective-c\fR" 4
486
.IX Item "-x objective-c"
487
.IP "\fB\-x assembler-with-cpp\fR" 4
488
.IX Item "-x assembler-with-cpp"
489
.PD
490
Specify the source language: C, \*(C+, Objective\-C, or assembly.  This has
491
nothing to do with standards conformance or extensions; it merely
492
selects which base syntax to expect.  If you give none of these options,
493
cpp will deduce the language from the extension of the source file:
494
\&\fB.c\fR, \fB.cc\fR, \fB.m\fR, or \fB.S\fR.  Some other common
495
extensions for \*(C+ and assembly are also recognized.  If cpp does not
496
recognize the extension, it will treat the file as C; this is the most
497
generic mode.
498
.Sp
499
\&\fINote:\fR Previous versions of cpp accepted a \fB\-lang\fR option
500
which selected both the language and the standards conformance level.
501
This option has been removed, because it conflicts with the \fB\-l\fR
502
option.
503
.IP "\fB\-std=\fR\fIstandard\fR" 4
504
.IX Item "-std=standard"
505
.PD 0
506
.IP "\fB\-ansi\fR" 4
507
.IX Item "-ansi"
508
.PD
509
Specify the standard to which the code should conform.  Currently \s-1CPP\s0
510
knows about C and \*(C+ standards; others may be added in the future.
511
.Sp
512
\&\fIstandard\fR
513
may be one of:
514
.RS 4
515
.ie n .IP """iso9899:1990""" 4
516
.el .IP "\f(CWiso9899:1990\fR" 4
517
.IX Item "iso9899:1990"
518
.PD 0
519
.ie n .IP """c89""" 4
520
.el .IP "\f(CWc89\fR" 4
521
.IX Item "c89"
522
.PD
523
The \s-1ISO\s0 C standard from 1990.  \fBc89\fR is the customary shorthand for
524
this version of the standard.
525
.Sp
526
The \fB\-ansi\fR option is equivalent to \fB\-std=c89\fR.
527
.ie n .IP """iso9899:199409""" 4
528
.el .IP "\f(CWiso9899:199409\fR" 4
529
.IX Item "iso9899:199409"
530
The 1990 C standard, as amended in 1994.
531
.ie n .IP """iso9899:1999""" 4
532
.el .IP "\f(CWiso9899:1999\fR" 4
533
.IX Item "iso9899:1999"
534
.PD 0
535
.ie n .IP """c99""" 4
536
.el .IP "\f(CWc99\fR" 4
537
.IX Item "c99"
538
.ie n .IP """iso9899:199x""" 4
539
.el .IP "\f(CWiso9899:199x\fR" 4
540
.IX Item "iso9899:199x"
541
.ie n .IP """c9x""" 4
542
.el .IP "\f(CWc9x\fR" 4
543
.IX Item "c9x"
544
.PD
545
The revised \s-1ISO\s0 C standard, published in December 1999.  Before
546
publication, this was known as C9X.
547
.ie n .IP """gnu89""" 4
548
.el .IP "\f(CWgnu89\fR" 4
549
.IX Item "gnu89"
550
The 1990 C standard plus \s-1GNU\s0 extensions.  This is the default.
551
.ie n .IP """gnu99""" 4
552
.el .IP "\f(CWgnu99\fR" 4
553
.IX Item "gnu99"
554
.PD 0
555
.ie n .IP """gnu9x""" 4
556
.el .IP "\f(CWgnu9x\fR" 4
557
.IX Item "gnu9x"
558
.PD
559
The 1999 C standard plus \s-1GNU\s0 extensions.
560
.ie n .IP """c++98""" 4
561
.el .IP "\f(CWc++98\fR" 4
562
.IX Item "c++98"
563
The 1998 \s-1ISO\s0 \*(C+ standard plus amendments.
564
.ie n .IP """gnu++98""" 4
565
.el .IP "\f(CWgnu++98\fR" 4
566
.IX Item "gnu++98"
567
The same as \fB\-std=c++98\fR plus \s-1GNU\s0 extensions.  This is the
568
default for \*(C+ code.
569
.RE
570
.RS 4
571
.RE
572
.IP "\fB\-I\-\fR" 4
573
.IX Item "-I-"
574
Split the include path.  Any directories specified with \fB\-I\fR
575
options before \fB\-I\-\fR are searched only for headers requested with
576
\&\f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR; they are not searched for
577
\&\f(CW\*(C`#include\ <\f(CIfile\f(CW>\*(C'\fR.  If additional directories are
578
specified with \fB\-I\fR options after the \fB\-I\-\fR, those
579
directories are searched for all \fB#include\fR directives.
580
.Sp
581
In addition, \fB\-I\-\fR inhibits the use of the directory of the current
582
file directory as the first search directory for \f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR.
583
.Sp
584
This option has been deprecated.
585
.IP "\fB\-nostdinc\fR" 4
586
.IX Item "-nostdinc"
587
Do not search the standard system directories for header files.
588
Only the directories you have specified with \fB\-I\fR options
589
(and the directory of the current file, if appropriate) are searched.
590
.IP "\fB\-nostdinc++\fR" 4
591
.IX Item "-nostdinc++"
592
Do not search for header files in the \*(C+\-specific standard directories,
593
but do still search the other standard directories.  (This option is
594
used when building the \*(C+ library.)
595
.IP "\fB\-include\fR \fIfile\fR" 4
596
.IX Item "-include file"
597
Process \fIfile\fR as if \f(CW\*(C`#include "file"\*(C'\fR appeared as the first
598
line of the primary source file.  However, the first directory searched
599
for \fIfile\fR is the preprocessor's working directory \fIinstead of\fR
600
the directory containing the main source file.  If not found there, it
601
is searched for in the remainder of the \f(CW\*(C`#include "..."\*(C'\fR search
602
chain as normal.
603
.Sp
604
If multiple \fB\-include\fR options are given, the files are included
605
in the order they appear on the command line.
606
.IP "\fB\-imacros\fR \fIfile\fR" 4
607
.IX Item "-imacros file"
608
Exactly like \fB\-include\fR, except that any output produced by
609
scanning \fIfile\fR is thrown away.  Macros it defines remain defined.
610
This allows you to acquire all the macros from a header without also
611
processing its declarations.
612
.Sp
613
All files specified by \fB\-imacros\fR are processed before all files
614
specified by \fB\-include\fR.
615
.IP "\fB\-idirafter\fR \fIdir\fR" 4
616
.IX Item "-idirafter dir"
617
Search \fIdir\fR for header files, but do it \fIafter\fR all
618
directories specified with \fB\-I\fR and the standard system directories
619
have been exhausted.  \fIdir\fR is treated as a system include directory.
620
.IP "\fB\-iprefix\fR \fIprefix\fR" 4
621
.IX Item "-iprefix prefix"
622
Specify \fIprefix\fR as the prefix for subsequent \fB\-iwithprefix\fR
623
options.  If the prefix represents a directory, you should include the
624
final \fB/\fR.
625
.IP "\fB\-iwithprefix\fR \fIdir\fR" 4
626
.IX Item "-iwithprefix dir"
627
.PD 0
628
.IP "\fB\-iwithprefixbefore\fR \fIdir\fR" 4
629
.IX Item "-iwithprefixbefore dir"
630
.PD
631
Append \fIdir\fR to the prefix specified previously with
632
\&\fB\-iprefix\fR, and add the resulting directory to the include search
633
path.  \fB\-iwithprefixbefore\fR puts it in the same place \fB\-I\fR
634
would; \fB\-iwithprefix\fR puts it where \fB\-idirafter\fR would.
635
.IP "\fB\-isysroot\fR \fIdir\fR" 4
636
.IX Item "-isysroot dir"
637
This option is like the \fB\-\-sysroot\fR option, but applies only to
638
header files.  See the \fB\-\-sysroot\fR option for more information.
639
.IP "\fB\-imultilib\fR \fIdir\fR" 4
640
.IX Item "-imultilib dir"
641
Use \fIdir\fR as a subdirectory of the directory containing
642
target-specific \*(C+ headers.
643
.IP "\fB\-isystem\fR \fIdir\fR" 4
644
.IX Item "-isystem dir"
645
Search \fIdir\fR for header files, after all directories specified by
646
\&\fB\-I\fR but before the standard system directories.  Mark it
647
as a system directory, so that it gets the same special treatment as
648
is applied to the standard system directories.
649
.IP "\fB\-iquote\fR \fIdir\fR" 4
650
.IX Item "-iquote dir"
651
Search \fIdir\fR only for header files requested with
652
\&\f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR; they are not searched for
653
\&\f(CW\*(C`#include\ <\f(CIfile\f(CW>\*(C'\fR, before all directories specified by
654
\&\fB\-I\fR and before the standard system directories.
655
.IP "\fB\-fdollars\-in\-identifiers\fR" 4
656
.IX Item "-fdollars-in-identifiers"
657
Accept \fB$\fR in identifiers.
658
.IP "\fB\-fextended\-identifiers\fR" 4
659
.IX Item "-fextended-identifiers"
660
Accept universal character names in identifiers.  This option is
661
experimental; in a future version of \s-1GCC\s0, it will be enabled by
662
default for C99 and \*(C+.
663
.IP "\fB\-fpreprocessed\fR" 4
664
.IX Item "-fpreprocessed"
665
Indicate to the preprocessor that the input file has already been
666
preprocessed.  This suppresses things like macro expansion, trigraph
667
conversion, escaped newline splicing, and processing of most directives.
668
The preprocessor still recognizes and removes comments, so that you can
669
pass a file preprocessed with \fB\-C\fR to the compiler without
670
problems.  In this mode the integrated preprocessor is little more than
671
a tokenizer for the front ends.
672
.Sp
673
\&\fB\-fpreprocessed\fR is implicit if the input file has one of the
674
extensions \fB.i\fR, \fB.ii\fR or \fB.mi\fR.  These are the
675
extensions that \s-1GCC\s0 uses for preprocessed files created by
676
\&\fB\-save\-temps\fR.
677
.IP "\fB\-ftabstop=\fR\fIwidth\fR" 4
678
.IX Item "-ftabstop=width"
679
Set the distance between tab stops.  This helps the preprocessor report
680
correct column numbers in warnings or errors, even if tabs appear on the
681
line.  If the value is less than 1 or greater than 100, the option is
682
ignored.  The default is 8.
683
.IP "\fB\-fexec\-charset=\fR\fIcharset\fR" 4
684
.IX Item "-fexec-charset=charset"
685
Set the execution character set, used for string and character
686
constants.  The default is \s-1UTF\-8\s0.  \fIcharset\fR can be any encoding
687
supported by the system's \f(CW\*(C`iconv\*(C'\fR library routine.
688
.IP "\fB\-fwide\-exec\-charset=\fR\fIcharset\fR" 4
689
.IX Item "-fwide-exec-charset=charset"
690
Set the wide execution character set, used for wide string and
691
character constants.  The default is \s-1UTF\-32\s0 or \s-1UTF\-16\s0, whichever
692
corresponds to the width of \f(CW\*(C`wchar_t\*(C'\fR.  As with
693
\&\fB\-fexec\-charset\fR, \fIcharset\fR can be any encoding supported
694
by the system's \f(CW\*(C`iconv\*(C'\fR library routine; however, you will have
695
problems with encodings that do not fit exactly in \f(CW\*(C`wchar_t\*(C'\fR.
696
.IP "\fB\-finput\-charset=\fR\fIcharset\fR" 4
697
.IX Item "-finput-charset=charset"
698
Set the input character set, used for translation from the character
699
set of the input file to the source character set used by \s-1GCC\s0.  If the
700
locale does not specify, or \s-1GCC\s0 cannot get this information from the
701
locale, the default is \s-1UTF\-8\s0.  This can be overridden by either the locale
702
or this command line option.  Currently the command line option takes
703
precedence if there's a conflict.  \fIcharset\fR can be any encoding
704
supported by the system's \f(CW\*(C`iconv\*(C'\fR library routine.
705
.IP "\fB\-fworking\-directory\fR" 4
706
.IX Item "-fworking-directory"
707
Enable generation of linemarkers in the preprocessor output that will
708
let the compiler know the current working directory at the time of
709
preprocessing.  When this option is enabled, the preprocessor will
710
emit, after the initial linemarker, a second linemarker with the
711
current working directory followed by two slashes.  \s-1GCC\s0 will use this
712
directory, when it's present in the preprocessed input, as the
713
directory emitted as the current working directory in some debugging
714
information formats.  This option is implicitly enabled if debugging
715
information is enabled, but this can be inhibited with the negated
716
form \fB\-fno\-working\-directory\fR.  If the \fB\-P\fR flag is
717
present in the command line, this option has no effect, since no
718
\&\f(CW\*(C`#line\*(C'\fR directives are emitted whatsoever.
719
.IP "\fB\-fno\-show\-column\fR" 4
720
.IX Item "-fno-show-column"
721
Do not print column numbers in diagnostics.  This may be necessary if
722
diagnostics are being scanned by a program that does not understand the
723
column numbers, such as \fBdejagnu\fR.
724
.IP "\fB\-A\fR \fIpredicate\fR\fB=\fR\fIanswer\fR" 4
725
.IX Item "-A predicate=answer"
726
Make an assertion with the predicate \fIpredicate\fR and answer
727
\&\fIanswer\fR.  This form is preferred to the older form \fB\-A\fR
728
\&\fIpredicate\fR\fB(\fR\fIanswer\fR\fB)\fR, which is still supported, because
729
it does not use shell special characters.
730
.IP "\fB\-A \-\fR\fIpredicate\fR\fB=\fR\fIanswer\fR" 4
731
.IX Item "-A -predicate=answer"
732
Cancel an assertion with the predicate \fIpredicate\fR and answer
733
\&\fIanswer\fR.
734
.IP "\fB\-dCHARS\fR" 4
735
.IX Item "-dCHARS"
736
\&\fI\s-1CHARS\s0\fR is a sequence of one or more of the following characters,
737
and must not be preceded by a space.  Other characters are interpreted
738
by the compiler proper, or reserved for future versions of \s-1GCC\s0, and so
739
are silently ignored.  If you specify characters whose behavior
740
conflicts, the result is undefined.
741
.RS 4
742
.IP "\fBM\fR" 4
743
.IX Item "M"
744
Instead of the normal output, generate a list of \fB#define\fR
745
directives for all the macros defined during the execution of the
746
preprocessor, including predefined macros.  This gives you a way of
747
finding out what is predefined in your version of the preprocessor.
748
Assuming you have no file \fIfoo.h\fR, the command
749
.Sp
750
.Vb 1
751
\&        touch foo.h; cpp -dM foo.h
752
.Ve
753
.Sp
754
will show all the predefined macros.
755
.IP "\fBD\fR" 4
756
.IX Item "D"
757
Like \fBM\fR except in two respects: it does \fInot\fR include the
758
predefined macros, and it outputs \fIboth\fR the \fB#define\fR
759
directives and the result of preprocessing.  Both kinds of output go to
760
the standard output file.
761
.IP "\fBN\fR" 4
762
.IX Item "N"
763
Like \fBD\fR, but emit only the macro names, not their expansions.
764
.IP "\fBI\fR" 4
765
.IX Item "I"
766
Output \fB#include\fR directives in addition to the result of
767
preprocessing.
768
.RE
769
.RS 4
770
.RE
771
.IP "\fB\-P\fR" 4
772
.IX Item "-P"
773
Inhibit generation of linemarkers in the output from the preprocessor.
774
This might be useful when running the preprocessor on something that is
775
not C code, and will be sent to a program which might be confused by the
776
linemarkers.
777
.IP "\fB\-C\fR" 4
778
.IX Item "-C"
779
Do not discard comments.  All comments are passed through to the output
780
file, except for comments in processed directives, which are deleted
781
along with the directive.
782
.Sp
783
You should be prepared for side effects when using \fB\-C\fR; it
784
causes the preprocessor to treat comments as tokens in their own right.
785
For example, comments appearing at the start of what would be a
786
directive line have the effect of turning that line into an ordinary
787
source line, since the first token on the line is no longer a \fB#\fR.
788
.IP "\fB\-CC\fR" 4
789
.IX Item "-CC"
790
Do not discard comments, including during macro expansion.  This is
791
like \fB\-C\fR, except that comments contained within macros are
792
also passed through to the output file where the macro is expanded.
793
.Sp
794
In addition to the side-effects of the \fB\-C\fR option, the
795
\&\fB\-CC\fR option causes all \*(C+\-style comments inside a macro
796
to be converted to C\-style comments.  This is to prevent later use
797
of that macro from inadvertently commenting out the remainder of
798
the source line.
799
.Sp
800
The \fB\-CC\fR option is generally used to support lint comments.
801
.IP "\fB\-traditional\-cpp\fR" 4
802
.IX Item "-traditional-cpp"
803
Try to imitate the behavior of old-fashioned C preprocessors, as
804
opposed to \s-1ISO\s0 C preprocessors.
805
.IP "\fB\-trigraphs\fR" 4
806
.IX Item "-trigraphs"
807
Process trigraph sequences.
808
.IP "\fB\-remap\fR" 4
809
.IX Item "-remap"
810
Enable special code to work around file systems which only permit very
811
short file names, such as \s-1MS\-DOS\s0.
812
.IP "\fB\-\-help\fR" 4
813
.IX Item "--help"
814
.PD 0
815
.IP "\fB\-\-target\-help\fR" 4
816
.IX Item "--target-help"
817
.PD
818
Print text describing all the command line options instead of
819
preprocessing anything.
820
.IP "\fB\-v\fR" 4
821
.IX Item "-v"
822
Verbose mode.  Print out \s-1GNU\s0 \s-1CPP\s0's version number at the beginning of
823
execution, and report the final form of the include path.
824
.IP "\fB\-H\fR" 4
825
.IX Item "-H"
826
Print the name of each header file used, in addition to other normal
827
activities.  Each name is indented to show how deep in the
828
\&\fB#include\fR stack it is.  Precompiled header files are also
829
printed, even if they are found to be invalid; an invalid precompiled
830
header file is printed with \fB...x\fR and a valid one with \fB...!\fR .
831
.IP "\fB\-version\fR" 4
832
.IX Item "-version"
833
.PD 0
834
.IP "\fB\-\-version\fR" 4
835
.IX Item "--version"
836
.PD
837
Print out \s-1GNU\s0 \s-1CPP\s0's version number.  With one dash, proceed to
838
preprocess as normal.  With two dashes, exit immediately.
839
.SH "ENVIRONMENT"
840
.IX Header "ENVIRONMENT"
841
This section describes the environment variables that affect how \s-1CPP\s0
842
operates.  You can use them to specify directories or prefixes to use
843
when searching for include files, or to control dependency output.
844
.PP
845
Note that you can also specify places to search using options such as
846
\&\fB\-I\fR, and control dependency output with options like
847
\&\fB\-M\fR.  These take precedence over
848
environment variables, which in turn take precedence over the
849
configuration of \s-1GCC\s0.
850
.IP "\fB\s-1CPATH\s0\fR" 4
851
.IX Item "CPATH"
852
.PD 0
853
.IP "\fBC_INCLUDE_PATH\fR" 4
854
.IX Item "C_INCLUDE_PATH"
855
.IP "\fB\s-1CPLUS_INCLUDE_PATH\s0\fR" 4
856
.IX Item "CPLUS_INCLUDE_PATH"
857
.IP "\fB\s-1OBJC_INCLUDE_PATH\s0\fR" 4
858
.IX Item "OBJC_INCLUDE_PATH"
859
.PD
860
Each variable's value is a list of directories separated by a special
861
character, much like \fB\s-1PATH\s0\fR, in which to look for header files.
862
The special character, \f(CW\*(C`PATH_SEPARATOR\*(C'\fR, is target-dependent and
863
determined at \s-1GCC\s0 build time.  For Microsoft Windows-based targets it is a
864
semicolon, and for almost all other targets it is a colon.
865
.Sp
866
\&\fB\s-1CPATH\s0\fR specifies a list of directories to be searched as if
867
specified with \fB\-I\fR, but after any paths given with \fB\-I\fR
868
options on the command line.  This environment variable is used
869
regardless of which language is being preprocessed.
870
.Sp
871
The remaining environment variables apply only when preprocessing the
872
particular language indicated.  Each specifies a list of directories
873
to be searched as if specified with \fB\-isystem\fR, but after any
874
paths given with \fB\-isystem\fR options on the command line.
875
.Sp
876
In all these variables, an empty element instructs the compiler to
877
search its current working directory.  Empty elements can appear at the
878
beginning or end of a path.  For instance, if the value of
879
\&\fB\s-1CPATH\s0\fR is \f(CW\*(C`:/special/include\*(C'\fR, that has the same
880
effect as \fB\-I.\ \-I/special/include\fR.
881
.IP "\fB\s-1DEPENDENCIES_OUTPUT\s0\fR" 4
882
.IX Item "DEPENDENCIES_OUTPUT"
883
If this variable is set, its value specifies how to output
884
dependencies for Make based on the non-system header files processed
885
by the compiler.  System header files are ignored in the dependency
886
output.
887
.Sp
888
The value of \fB\s-1DEPENDENCIES_OUTPUT\s0\fR can be just a file name, in
889
which case the Make rules are written to that file, guessing the target
890
name from the source file name.  Or the value can have the form
891
\&\fIfile\fR\fB \fR\fItarget\fR, in which case the rules are written to
892
file \fIfile\fR using \fItarget\fR as the target name.
893
.Sp
894
In other words, this environment variable is equivalent to combining
895
the options \fB\-MM\fR and \fB\-MF\fR,
896
with an optional \fB\-MT\fR switch too.
897
.IP "\fB\s-1SUNPRO_DEPENDENCIES\s0\fR" 4
898
.IX Item "SUNPRO_DEPENDENCIES"
899
This variable is the same as \fB\s-1DEPENDENCIES_OUTPUT\s0\fR (see above),
900
except that system header files are not ignored, so it implies
901
\&\fB\-M\fR rather than \fB\-MM\fR.  However, the dependence on the
902
main input file is omitted.
903
.SH "SEE ALSO"
904
.IX Header "SEE ALSO"
905
\&\fIgpl\fR\|(7), \fIgfdl\fR\|(7), \fIfsf\-funding\fR\|(7),
906
\&\fIgcc\fR\|(1), \fIas\fR\|(1), \fIld\fR\|(1), and the Info entries for \fIcpp\fR, \fIgcc\fR, and
907
\&\fIbinutils\fR.
908
.SH "COPYRIGHT"
909
.IX Header "COPYRIGHT"
910
Copyright (c) 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996,
911
1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
912
Free Software Foundation, Inc.
913
.PP
914
Permission is granted to copy, distribute and/or modify this document
915
under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.1 or
916
any later version published by the Free Software Foundation.  A copy of
917
the license is included in the
918
man page \fIgfdl\fR\|(7).
919
This manual contains no Invariant Sections.  The Front-Cover Texts are
920
(a) (see below), and the Back-Cover Texts are (b) (see below).
921
.PP
922
(a) The \s-1FSF\s0's Front-Cover Text is:
923
.PP
924
.Vb 1
925
\&     A GNU Manual
926
.Ve
927
.PP
928
(b) The \s-1FSF\s0's Back-Cover Text is:
929
.PP
930
.Vb 3
931
\&     You have freedom to copy and modify this GNU Manual, like GNU
932
\&     software.  Copies published by the Free Software Foundation raise
933
\&     funds for GNU development.
934
.Ve

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