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129 .\" ========================================================================
132 .TH CPP 1 "2007-02-14" "gcc-4.1.2" "GNU"
134 cpp \- The C Preprocessor
136 .IX Header "SYNOPSIS"
137 cpp [\fB\-D\fR\fImacro\fR[=\fIdefn\fR]...] [\fB\-U\fR\fImacro\fR]
138 [\fB\-I\fR\fIdir\fR...] [\fB\-iquote\fR\fIdir\fR...]
139 [\fB\-W\fR\fIwarn\fR...]
140 [\fB\-M\fR|\fB\-MM\fR] [\fB\-MG\fR] [\fB\-MF\fR \fIfilename\fR]
141 [\fB\-MP\fR] [\fB\-MQ\fR \fItarget\fR...]
142 [\fB\-MT\fR \fItarget\fR...]
143 [\fB\-P\fR] [\fB\-fno\-working\-directory\fR]
144 [\fB\-x\fR \fIlanguage\fR] [\fB\-std=\fR\fIstandard\fR]
145 \fIinfile\fR \fIoutfile\fR
147 Only the most useful options are listed here; see below for the remainder.
149 .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
156 The C preprocessor is intended to be used only with C, \*(C+, and
157 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
162 C\-family languages. If a Makefile is preprocessed, all the hard tabs
163 will be removed, and the Makefile will not work.
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
168 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.
172 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.
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
180 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.
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
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.
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.
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.
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.
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
217 .IP "\fB\-D\fR \fIname\fR" 4
219 Predefine \fIname\fR as a macro, with definition \f(CW1\fR.
220 .IP "\fB\-D\fR \fIname\fR\fB=\fR\fIdefinition\fR" 4
221 .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
224 directive. In particular, the definition will be truncated by
225 embedded newline characters.
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.
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.
237 \&\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
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
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
251 Add the directory \fIdir\fR to the list of directories to be searched
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
260 .IP "\fB\-o\fR \fIfile\fR" 4
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.
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
274 .IP "\fB\-Wcomment\fR" 4
277 .IP "\fB\-Wcomments\fR" 4
278 .IX Item "-Wcomments"
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"
286 Most trigraphs in comments cannot affect the meaning of the program.
287 However, a trigraph that would form an escaped newline (\fB??/\fR at
288 the end of a line) can, by changing where the comment begins or ends.
289 Therefore, only trigraphs that would form escaped newlines produce
290 warnings inside a comment.
292 This option is implied by \fB\-Wall\fR. If \fB\-Wall\fR is not
293 given, this option is still enabled unless trigraphs are enabled. To
294 get trigraph conversion without warnings, but get the other
295 \&\fB\-Wall\fR warnings, use \fB\-trigraphs \-Wall \-Wno\-trigraphs\fR.
296 .IP "\fB\-Wtraditional\fR" 4
297 .IX Item "-Wtraditional"
298 Warn about certain constructs that behave differently in traditional and
299 \&\s-1ISO\s0 C. Also warn about \s-1ISO\s0 C constructs that have no traditional C
300 equivalent, and problematic constructs which should be avoided.
301 .IP "\fB\-Wimport\fR" 4
303 Warn the first time \fB#import\fR is used.
304 .IP "\fB\-Wundef\fR" 4
306 Warn whenever an identifier which is not a macro is encountered in an
307 \&\fB#if\fR directive, outside of \fBdefined\fR. Such identifiers are
309 .IP "\fB\-Wunused\-macros\fR" 4
310 .IX Item "-Wunused-macros"
311 Warn about macros defined in the main file that are unused. A macro
312 is \fIused\fR if it is expanded or tested for existence at least once.
313 The preprocessor will also warn if the macro has not been used at the
314 time it is redefined or undefined.
316 Built-in macros, macros defined on the command line, and macros
317 defined in include files are not warned about.
319 \&\fINote:\fR If a macro is actually used, but only used in skipped
320 conditional blocks, then \s-1CPP\s0 will report it as unused. To avoid the
321 warning in such a case, you might improve the scope of the macro's
322 definition by, for example, moving it into the first skipped block.
323 Alternatively, you could provide a dummy use with something like:
326 \& #if defined the_macro_causing_the_warning
329 .IP "\fB\-Wendif\-labels\fR" 4
330 .IX Item "-Wendif-labels"
331 Warn whenever an \fB#else\fR or an \fB#endif\fR are followed by text.
332 This usually happens in code of the form
342 The second and third \f(CW\*(C`FOO\*(C'\fR should be in comments, but often are not
343 in older programs. This warning is on by default.
344 .IP "\fB\-Werror\fR" 4
346 Make all warnings into hard errors. Source code which triggers warnings
348 .IP "\fB\-Wsystem\-headers\fR" 4
349 .IX Item "-Wsystem-headers"
350 Issue warnings for code in system headers. These are normally unhelpful
351 in finding bugs in your own code, therefore suppressed. If you are
352 responsible for the system library, you may want to see them.
355 Suppress all warnings, including those which \s-1GNU\s0 \s-1CPP\s0 issues by default.
356 .IP "\fB\-pedantic\fR" 4
358 Issue all the mandatory diagnostics listed in the C standard. Some of
359 them are left out by default, since they trigger frequently on harmless
361 .IP "\fB\-pedantic\-errors\fR" 4
362 .IX Item "-pedantic-errors"
363 Issue all the mandatory diagnostics, and make all mandatory diagnostics
364 into errors. This includes mandatory diagnostics that \s-1GCC\s0 issues
365 without \fB\-pedantic\fR but treats as warnings.
368 Instead of outputting the result of preprocessing, output a rule
369 suitable for \fBmake\fR describing the dependencies of the main
370 source file. The preprocessor outputs one \fBmake\fR rule containing
371 the object file name for that source file, a colon, and the names of all
372 the included files, including those coming from \fB\-include\fR or
373 \&\fB\-imacros\fR command line options.
375 Unless specified explicitly (with \fB\-MT\fR or \fB\-MQ\fR), the
376 object file name consists of the basename of the source file with any
377 suffix replaced with object file suffix. If there are many included
378 files then the rule is split into several lines using \fB\e\fR\-newline.
379 The rule has no commands.
381 This option does not suppress the preprocessor's debug output, such as
382 \&\fB\-dM\fR. To avoid mixing such debug output with the dependency
383 rules you should explicitly specify the dependency output file with
384 \&\fB\-MF\fR, or use an environment variable like
385 \&\fB\s-1DEPENDENCIES_OUTPUT\s0\fR. Debug output
386 will still be sent to the regular output stream as normal.
388 Passing \fB\-M\fR to the driver implies \fB\-E\fR, and suppresses
389 warnings with an implicit \fB\-w\fR.
392 Like \fB\-M\fR but do not mention header files that are found in
393 system header directories, nor header files that are included,
394 directly or indirectly, from such a header.
396 This implies that the choice of angle brackets or double quotes in an
397 \&\fB#include\fR directive does not in itself determine whether that
398 header will appear in \fB\-MM\fR dependency output. This is a
399 slight change in semantics from \s-1GCC\s0 versions 3.0 and earlier.
402 .IP "\fB\-MF\fR \fIfile\fR" 4
404 When used with \fB\-M\fR or \fB\-MM\fR, specifies a
405 file to write the dependencies to. If no \fB\-MF\fR switch is given
406 the preprocessor sends the rules to the same place it would have sent
409 When used with the driver options \fB\-MD\fR or \fB\-MMD\fR,
410 \&\fB\-MF\fR overrides the default dependency output file.
413 In conjunction with an option such as \fB\-M\fR requesting
414 dependency generation, \fB\-MG\fR assumes missing header files are
415 generated files and adds them to the dependency list without raising
416 an error. The dependency filename is taken directly from the
417 \&\f(CW\*(C`#include\*(C'\fR directive without prepending any path. \fB\-MG\fR
418 also suppresses preprocessed output, as a missing header file renders
421 This feature is used in automatic updating of makefiles.
424 This option instructs \s-1CPP\s0 to add a phony target for each dependency
425 other than the main file, causing each to depend on nothing. These
426 dummy rules work around errors \fBmake\fR gives if you remove header
427 files without updating the \fIMakefile\fR to match.
429 This is typical output:
432 \& test.o: test.c test.h
438 .IP "\fB\-MT\fR \fItarget\fR" 4
439 .IX Item "-MT target"
440 Change the target of the rule emitted by dependency generation. By
441 default \s-1CPP\s0 takes the name of the main input file, including any path,
442 deletes any file suffix such as \fB.c\fR, and appends the platform's
443 usual object suffix. The result is the target.
445 An \fB\-MT\fR option will set the target to be exactly the string you
446 specify. If you want multiple targets, you can specify them as a single
447 argument to \fB\-MT\fR, or use multiple \fB\-MT\fR options.
449 For example, \fB\-MT\ '$(objpfx)foo.o'\fR might give
452 \& $(objpfx)foo.o: foo.c
454 .IP "\fB\-MQ\fR \fItarget\fR" 4
455 .IX Item "-MQ target"
456 Same as \fB\-MT\fR, but it quotes any characters which are special to
457 Make. \fB\-MQ\ '$(objpfx)foo.o'\fR gives
460 \& $$(objpfx)foo.o: foo.c
463 The default target is automatically quoted, as if it were given with
467 \&\fB\-MD\fR is equivalent to \fB\-M \-MF\fR \fIfile\fR, except that
468 \&\fB\-E\fR is not implied. The driver determines \fIfile\fR based on
469 whether an \fB\-o\fR option is given. If it is, the driver uses its
470 argument but with a suffix of \fI.d\fR, otherwise it take the
471 basename of the input file and applies a \fI.d\fR suffix.
473 If \fB\-MD\fR is used in conjunction with \fB\-E\fR, any
474 \&\fB\-o\fR switch is understood to specify the dependency output file
475 (but \f(CW@pxref\fR{dashMF,,\-MF}), but if used without \fB\-E\fR, each \fB\-o\fR
476 is understood to specify a target object file.
478 Since \fB\-E\fR is not implied, \fB\-MD\fR can be used to generate
479 a dependency output file as a side-effect of the compilation process.
482 Like \fB\-MD\fR except mention only user header files, not system
487 .IP "\fB\-x c++\fR" 4
489 .IP "\fB\-x objective-c\fR" 4
490 .IX Item "-x objective-c"
491 .IP "\fB\-x assembler-with-cpp\fR" 4
492 .IX Item "-x assembler-with-cpp"
494 Specify the source language: C, \*(C+, Objective\-C, or assembly. This has
495 nothing to do with standards conformance or extensions; it merely
496 selects which base syntax to expect. If you give none of these options,
497 cpp will deduce the language from the extension of the source file:
498 \&\fB.c\fR, \fB.cc\fR, \fB.m\fR, or \fB.S\fR. Some other common
499 extensions for \*(C+ and assembly are also recognized. If cpp does not
500 recognize the extension, it will treat the file as C; this is the most
503 \&\fINote:\fR Previous versions of cpp accepted a \fB\-lang\fR option
504 which selected both the language and the standards conformance level.
505 This option has been removed, because it conflicts with the \fB\-l\fR
507 .IP "\fB\-std=\fR\fIstandard\fR" 4
508 .IX Item "-std=standard"
513 Specify the standard to which the code should conform. Currently \s-1CPP\s0
514 knows about C and \*(C+ standards; others may be added in the future.
519 .ie n .IP """iso9899:1990""" 4
520 .el .IP "\f(CWiso9899:1990\fR" 4
521 .IX Item "iso9899:1990"
523 .ie n .IP """c89""" 4
524 .el .IP "\f(CWc89\fR" 4
527 The \s-1ISO\s0 C standard from 1990. \fBc89\fR is the customary shorthand for
528 this version of the standard.
530 The \fB\-ansi\fR option is equivalent to \fB\-std=c89\fR.
531 .ie n .IP """iso9899:199409""" 4
532 .el .IP "\f(CWiso9899:199409\fR" 4
533 .IX Item "iso9899:199409"
534 The 1990 C standard, as amended in 1994.
535 .ie n .IP """iso9899:1999""" 4
536 .el .IP "\f(CWiso9899:1999\fR" 4
537 .IX Item "iso9899:1999"
539 .ie n .IP """c99""" 4
540 .el .IP "\f(CWc99\fR" 4
542 .ie n .IP """iso9899:199x""" 4
543 .el .IP "\f(CWiso9899:199x\fR" 4
544 .IX Item "iso9899:199x"
545 .ie n .IP """c9x""" 4
546 .el .IP "\f(CWc9x\fR" 4
549 The revised \s-1ISO\s0 C standard, published in December 1999. Before
550 publication, this was known as C9X.
551 .ie n .IP """gnu89""" 4
552 .el .IP "\f(CWgnu89\fR" 4
554 The 1990 C standard plus \s-1GNU\s0 extensions. This is the default.
555 .ie n .IP """gnu99""" 4
556 .el .IP "\f(CWgnu99\fR" 4
559 .ie n .IP """gnu9x""" 4
560 .el .IP "\f(CWgnu9x\fR" 4
563 The 1999 C standard plus \s-1GNU\s0 extensions.
564 .ie n .IP """c++98""" 4
565 .el .IP "\f(CWc++98\fR" 4
567 The 1998 \s-1ISO\s0 \*(C+ standard plus amendments.
568 .ie n .IP """gnu++98""" 4
569 .el .IP "\f(CWgnu++98\fR" 4
571 The same as \fB\-std=c++98\fR plus \s-1GNU\s0 extensions. This is the
572 default for \*(C+ code.
578 Split the include path. Any directories specified with \fB\-I\fR
579 options before \fB\-I\-\fR are searched only for headers requested with
580 \&\f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR; they are not searched for
581 \&\f(CW\*(C`#include\ <\f(CIfile\f(CW>\*(C'\fR. If additional directories are
582 specified with \fB\-I\fR options after the \fB\-I\-\fR, those
583 directories are searched for all \fB#include\fR directives.
585 In addition, \fB\-I\-\fR inhibits the use of the directory of the current
586 file directory as the first search directory for \f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR.
588 This option has been deprecated.
589 .IP "\fB\-nostdinc\fR" 4
591 Do not search the standard system directories for header files.
592 Only the directories you have specified with \fB\-I\fR options
593 (and the directory of the current file, if appropriate) are searched.
594 .IP "\fB\-nostdinc++\fR" 4
595 .IX Item "-nostdinc++"
596 Do not search for header files in the \*(C+\-specific standard directories,
597 but do still search the other standard directories. (This option is
598 used when building the \*(C+ library.)
599 .IP "\fB\-include\fR \fIfile\fR" 4
600 .IX Item "-include file"
601 Process \fIfile\fR as if \f(CW\*(C`#include "file"\*(C'\fR appeared as the first
602 line of the primary source file. However, the first directory searched
603 for \fIfile\fR is the preprocessor's working directory \fIinstead of\fR
604 the directory containing the main source file. If not found there, it
605 is searched for in the remainder of the \f(CW\*(C`#include "..."\*(C'\fR search
608 If multiple \fB\-include\fR options are given, the files are included
609 in the order they appear on the command line.
610 .IP "\fB\-imacros\fR \fIfile\fR" 4
611 .IX Item "-imacros file"
612 Exactly like \fB\-include\fR, except that any output produced by
613 scanning \fIfile\fR is thrown away. Macros it defines remain defined.
614 This allows you to acquire all the macros from a header without also
615 processing its declarations.
617 All files specified by \fB\-imacros\fR are processed before all files
618 specified by \fB\-include\fR.
619 .IP "\fB\-idirafter\fR \fIdir\fR" 4
620 .IX Item "-idirafter dir"
621 Search \fIdir\fR for header files, but do it \fIafter\fR all
622 directories specified with \fB\-I\fR and the standard system directories
623 have been exhausted. \fIdir\fR is treated as a system include directory.
624 .IP "\fB\-iprefix\fR \fIprefix\fR" 4
625 .IX Item "-iprefix prefix"
626 Specify \fIprefix\fR as the prefix for subsequent \fB\-iwithprefix\fR
627 options. If the prefix represents a directory, you should include the
629 .IP "\fB\-iwithprefix\fR \fIdir\fR" 4
630 .IX Item "-iwithprefix dir"
632 .IP "\fB\-iwithprefixbefore\fR \fIdir\fR" 4
633 .IX Item "-iwithprefixbefore dir"
635 Append \fIdir\fR to the prefix specified previously with
636 \&\fB\-iprefix\fR, and add the resulting directory to the include search
637 path. \fB\-iwithprefixbefore\fR puts it in the same place \fB\-I\fR
638 would; \fB\-iwithprefix\fR puts it where \fB\-idirafter\fR would.
639 .IP "\fB\-isysroot\fR \fIdir\fR" 4
640 .IX Item "-isysroot dir"
641 This option is like the \fB\-\-sysroot\fR option, but applies only to
642 header files. See the \fB\-\-sysroot\fR option for more information.
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 @anchor{fdollars\-in\-identifiers}
658 Accept \fB$\fR in identifiers.
659 .IP "\fB\-fextended\-identifiers\fR" 4
660 .IX Item "-fextended-identifiers"
661 Accept universal character names in identifiers. This option is
662 experimental; in a future version of \s-1GCC\s0, it will be enabled by
663 default for C99 and \*(C+.
664 .IP "\fB\-fpreprocessed\fR" 4
665 .IX Item "-fpreprocessed"
666 Indicate to the preprocessor that the input file has already been
667 preprocessed. This suppresses things like macro expansion, trigraph
668 conversion, escaped newline splicing, and processing of most directives.
669 The preprocessor still recognizes and removes comments, so that you can
670 pass a file preprocessed with \fB\-C\fR to the compiler without
671 problems. In this mode the integrated preprocessor is little more than
672 a tokenizer for the front ends.
674 \&\fB\-fpreprocessed\fR is implicit if the input file has one of the
675 extensions \fB.i\fR, \fB.ii\fR or \fB.mi\fR. These are the
676 extensions that \s-1GCC\s0 uses for preprocessed files created by
677 \&\fB\-save\-temps\fR.
678 .IP "\fB\-ftabstop=\fR\fIwidth\fR" 4
679 .IX Item "-ftabstop=width"
680 Set the distance between tab stops. This helps the preprocessor report
681 correct column numbers in warnings or errors, even if tabs appear on the
682 line. If the value is less than 1 or greater than 100, the option is
683 ignored. The default is 8.
684 .IP "\fB\-fexec\-charset=\fR\fIcharset\fR" 4
685 .IX Item "-fexec-charset=charset"
686 Set the execution character set, used for string and character
687 constants. The default is \s-1UTF\-8\s0. \fIcharset\fR can be any encoding
688 supported by the system's \f(CW\*(C`iconv\*(C'\fR library routine.
689 .IP "\fB\-fwide\-exec\-charset=\fR\fIcharset\fR" 4
690 .IX Item "-fwide-exec-charset=charset"
691 Set the wide execution character set, used for wide string and
692 character constants. The default is \s-1UTF\-32\s0 or \s-1UTF\-16\s0, whichever
693 corresponds to the width of \f(CW\*(C`wchar_t\*(C'\fR. As with
694 \&\fB\-fexec\-charset\fR, \fIcharset\fR can be any encoding supported
695 by the system's \f(CW\*(C`iconv\*(C'\fR library routine; however, you will have
696 problems with encodings that do not fit exactly in \f(CW\*(C`wchar_t\*(C'\fR.
697 .IP "\fB\-finput\-charset=\fR\fIcharset\fR" 4
698 .IX Item "-finput-charset=charset"
699 Set the input character set, used for translation from the character
700 set of the input file to the source character set used by \s-1GCC\s0. If the
701 locale does not specify, or \s-1GCC\s0 cannot get this information from the
702 locale, the default is \s-1UTF\-8\s0. This can be overridden by either the locale
703 or this command line option. Currently the command line option takes
704 precedence if there's a conflict. \fIcharset\fR can be any encoding
705 supported by the system's \f(CW\*(C`iconv\*(C'\fR library routine.
706 .IP "\fB\-fworking\-directory\fR" 4
707 .IX Item "-fworking-directory"
708 Enable generation of linemarkers in the preprocessor output that will
709 let the compiler know the current working directory at the time of
710 preprocessing. When this option is enabled, the preprocessor will
711 emit, after the initial linemarker, a second linemarker with the
712 current working directory followed by two slashes. \s-1GCC\s0 will use this
713 directory, when it's present in the preprocessed input, as the
714 directory emitted as the current working directory in some debugging
715 information formats. This option is implicitly enabled if debugging
716 information is enabled, but this can be inhibited with the negated
717 form \fB\-fno\-working\-directory\fR. If the \fB\-P\fR flag is
718 present in the command line, this option has no effect, since no
719 \&\f(CW\*(C`#line\*(C'\fR directives are emitted whatsoever.
720 .IP "\fB\-fno\-show\-column\fR" 4
721 .IX Item "-fno-show-column"
722 Do not print column numbers in diagnostics. This may be necessary if
723 diagnostics are being scanned by a program that does not understand the
724 column numbers, such as \fBdejagnu\fR.
725 .IP "\fB\-A\fR \fIpredicate\fR\fB=\fR\fIanswer\fR" 4
726 .IX Item "-A predicate=answer"
727 Make an assertion with the predicate \fIpredicate\fR and answer
728 \&\fIanswer\fR. This form is preferred to the older form \fB\-A\fR
729 \&\fIpredicate\fR\fB(\fR\fIanswer\fR\fB)\fR, which is still supported, because
730 it does not use shell special characters.
731 .IP "\fB\-A \-\fR\fIpredicate\fR\fB=\fR\fIanswer\fR" 4
732 .IX Item "-A -predicate=answer"
733 Cancel an assertion with the predicate \fIpredicate\fR and answer
735 .IP "\fB\-dCHARS\fR" 4
737 \&\fI\s-1CHARS\s0\fR is a sequence of one or more of the following characters,
738 and must not be preceded by a space. Other characters are interpreted
739 by the compiler proper, or reserved for future versions of \s-1GCC\s0, and so
740 are silently ignored. If you specify characters whose behavior
741 conflicts, the result is undefined.
745 Instead of the normal output, generate a list of \fB#define\fR
746 directives for all the macros defined during the execution of the
747 preprocessor, including predefined macros. This gives you a way of
748 finding out what is predefined in your version of the preprocessor.
749 Assuming you have no file \fIfoo.h\fR, the command
752 \& touch foo.h; cpp -dM foo.h
755 will show all the predefined macros.
758 Like \fBM\fR except in two respects: it does \fInot\fR include the
759 predefined macros, and it outputs \fIboth\fR the \fB#define\fR
760 directives and the result of preprocessing. Both kinds of output go to
761 the standard output file.
764 Like \fBD\fR, but emit only the macro names, not their expansions.
767 Output \fB#include\fR directives in addition to the result of
774 Inhibit generation of linemarkers in the output from the preprocessor.
775 This might be useful when running the preprocessor on something that is
776 not C code, and will be sent to a program which might be confused by the
780 Do not discard comments. All comments are passed through to the output
781 file, except for comments in processed directives, which are deleted
782 along with the directive.
784 You should be prepared for side effects when using \fB\-C\fR; it
785 causes the preprocessor to treat comments as tokens in their own right.
786 For example, comments appearing at the start of what would be a
787 directive line have the effect of turning that line into an ordinary
788 source line, since the first token on the line is no longer a \fB#\fR.
791 Do not discard comments, including during macro expansion. This is
792 like \fB\-C\fR, except that comments contained within macros are
793 also passed through to the output file where the macro is expanded.
795 In addition to the side-effects of the \fB\-C\fR option, the
796 \&\fB\-CC\fR option causes all \*(C+\-style comments inside a macro
797 to be converted to C\-style comments. This is to prevent later use
798 of that macro from inadvertently commenting out the remainder of
801 The \fB\-CC\fR option is generally used to support lint comments.
802 .IP "\fB\-traditional\-cpp\fR" 4
803 .IX Item "-traditional-cpp"
804 Try to imitate the behavior of old-fashioned C preprocessors, as
805 opposed to \s-1ISO\s0 C preprocessors.
806 .IP "\fB\-trigraphs\fR" 4
807 .IX Item "-trigraphs"
808 Process trigraph sequences.
809 .IP "\fB\-remap\fR" 4
811 Enable special code to work around file systems which only permit very
812 short file names, such as \s-1MS\-DOS\s0.
813 .IP "\fB\-\-help\fR" 4
816 .IP "\fB\-\-target\-help\fR" 4
817 .IX Item "--target-help"
819 Print text describing all the command line options instead of
820 preprocessing anything.
823 Verbose mode. Print out \s-1GNU\s0 \s-1CPP\s0's version number at the beginning of
824 execution, and report the final form of the include path.
827 Print the name of each header file used, in addition to other normal
828 activities. Each name is indented to show how deep in the
829 \&\fB#include\fR stack it is. Precompiled header files are also
830 printed, even if they are found to be invalid; an invalid precompiled
831 header file is printed with \fB...x\fR and a valid one with \fB...!\fR .
832 .IP "\fB\-version\fR" 4
835 .IP "\fB\-\-version\fR" 4
838 Print out \s-1GNU\s0 \s-1CPP\s0's version number. With one dash, proceed to
839 preprocess as normal. With two dashes, exit immediately.
841 .IX Header "ENVIRONMENT"
842 This section describes the environment variables that affect how \s-1CPP\s0
843 operates. You can use them to specify directories or prefixes to use
844 when searching for include files, or to control dependency output.
846 Note that you can also specify places to search using options such as
847 \&\fB\-I\fR, and control dependency output with options like
848 \&\fB\-M\fR. These take precedence over
849 environment variables, which in turn take precedence over the
850 configuration of \s-1GCC\s0.
851 .IP "\fB\s-1CPATH\s0\fR" 4
854 .IP "\fBC_INCLUDE_PATH\fR" 4
855 .IX Item "C_INCLUDE_PATH"
856 .IP "\fB\s-1CPLUS_INCLUDE_PATH\s0\fR" 4
857 .IX Item "CPLUS_INCLUDE_PATH"
858 .IP "\fB\s-1OBJC_INCLUDE_PATH\s0\fR" 4
859 .IX Item "OBJC_INCLUDE_PATH"
861 Each variable's value is a list of directories separated by a special
862 character, much like \fB\s-1PATH\s0\fR, in which to look for header files.
863 The special character, \f(CW\*(C`PATH_SEPARATOR\*(C'\fR, is target-dependent and
864 determined at \s-1GCC\s0 build time. For Microsoft Windows-based targets it is a
865 semicolon, and for almost all other targets it is a colon.
867 \&\fB\s-1CPATH\s0\fR specifies a list of directories to be searched as if
868 specified with \fB\-I\fR, but after any paths given with \fB\-I\fR
869 options on the command line. This environment variable is used
870 regardless of which language is being preprocessed.
872 The remaining environment variables apply only when preprocessing the
873 particular language indicated. Each specifies a list of directories
874 to be searched as if specified with \fB\-isystem\fR, but after any
875 paths given with \fB\-isystem\fR options on the command line.
877 In all these variables, an empty element instructs the compiler to
878 search its current working directory. Empty elements can appear at the
879 beginning or end of a path. For instance, if the value of
880 \&\fB\s-1CPATH\s0\fR is \f(CW\*(C`:/special/include\*(C'\fR, that has the same
881 effect as \fB\-I.\ \-I/special/include\fR.
882 .IP "\fB\s-1DEPENDENCIES_OUTPUT\s0\fR" 4
883 .IX Item "DEPENDENCIES_OUTPUT"
884 If this variable is set, its value specifies how to output
885 dependencies for Make based on the non-system header files processed
886 by the compiler. System header files are ignored in the dependency
889 The value of \fB\s-1DEPENDENCIES_OUTPUT\s0\fR can be just a file name, in
890 which case the Make rules are written to that file, guessing the target
891 name from the source file name. Or the value can have the form
892 \&\fIfile\fR\fB \fR\fItarget\fR, in which case the rules are written to
893 file \fIfile\fR using \fItarget\fR as the target name.
895 In other words, this environment variable is equivalent to combining
896 the options \fB\-MM\fR and \fB\-MF\fR,
897 with an optional \fB\-MT\fR switch too.
898 .IP "\fB\s-1SUNPRO_DEPENDENCIES\s0\fR" 4
899 .IX Item "SUNPRO_DEPENDENCIES"
900 This variable is the same as \fB\s-1DEPENDENCIES_OUTPUT\s0\fR (see above),
901 except that system header files are not ignored, so it implies
902 \&\fB\-M\fR rather than \fB\-MM\fR. However, the dependence on the
903 main input file is omitted.
905 .IX Header "SEE ALSO"
906 \&\fIgpl\fR\|(7), \fIgfdl\fR\|(7), \fIfsf\-funding\fR\|(7),
907 \&\fIgcc\fR\|(1), \fIas\fR\|(1), \fIld\fR\|(1), and the Info entries for \fIcpp\fR, \fIgcc\fR, and
910 .IX Header "COPYRIGHT"
911 Copyright (c) 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996,
912 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
913 Free Software Foundation, Inc.
915 Permission is granted to copy, distribute and/or modify this document
916 under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.1 or
917 any later version published by the Free Software Foundation. A copy of
918 the license is included in the
919 man page \fIgfdl\fR\|(7).
920 This manual contains no Invariant Sections. The Front-Cover Texts are
921 (a) (see below), and the Back-Cover Texts are (b) (see below).
923 (a) The \s-1FSF\s0's Front-Cover Text is:
929 (b) The \s-1FSF\s0's Back-Cover Text is:
932 \& You have freedom to copy and modify this GNU Manual, like GNU
933 \& software. Copies published by the Free Software Foundation raise
934 \& funds for GNU development.
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