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129 .\" ========================================================================
132 .TH CPP 1 "2007-07-19" "gcc-4.2.1" "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 and \*(C+ source
157 code. In the past, it has been abused as a general text processor. It
158 will choke on input which does not obey C's lexical rules. For
159 example, apostrophes will be interpreted as the beginning of character
160 constants, and cause errors. Also, you cannot rely on it preserving
161 characteristics of the input which are not significant to C\-family
162 languages. If a Makefile is preprocessed, all the hard tabs will be
163 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"
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.
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
302 Warn the first time \fB#import\fR is used.
303 .IP "\fB\-Wundef\fR" 4
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
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.
315 Built-in macros, macros defined on the command line, and macros
316 defined in include files are not warned about.
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:
325 \& #if defined the_macro_causing_the_warning
328 .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
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
345 Make all warnings into hard errors. Source code which triggers warnings
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.
354 Suppress all warnings, including those which \s-1GNU\s0 \s-1CPP\s0 issues by default.
355 .IP "\fB\-pedantic\fR" 4
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
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.
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.
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.
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.
387 Passing \fB\-M\fR to the driver implies \fB\-E\fR, and suppresses
388 warnings with an implicit \fB\-w\fR.
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.
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
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
406 When used with the driver options \fB\-MD\fR or \fB\-MMD\fR,
407 \&\fB\-MF\fR overrides the default dependency output file.
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
418 This feature is used in automatic updating of makefiles.
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.
426 This is typical output:
429 \& test.o: test.c test.h
435 .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.
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.
446 For example, \fB\-MT\ '$(objpfx)foo.o'\fR might give
449 \& $(objpfx)foo.o: foo.c
451 .IP "\fB\-MQ\fR \fItarget\fR" 4
452 .IX Item "-MQ target"
453 Same as \fB\-MT\fR, but it quotes any characters which are special to
454 Make. \fB\-MQ\ '$(objpfx)foo.o'\fR gives
457 \& $$(objpfx)foo.o: foo.c
460 The default target is automatically quoted, as if it were given with
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.
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.
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.
478 Like \fB\-MD\fR except mention only user header files, not system
483 .IP "\fB\-x c++\fR" 4
485 .IP "\fB\-x assembler-with-cpp\fR" 4
486 .IX Item "-x assembler-with-cpp"
488 Specify the source language: C, \*(C+, or assembly. This has nothing
489 to do with standards conformance or extensions; it merely selects which
490 base syntax to expect. If you give none of these options, cpp will
491 deduce the language from the extension of the source file: \&\fB.c\fR,
492 \fB.cc\fR, or \fB.S\fR. Some other common extensions for \*(C+ and
493 assembly are also recognized. If cpp does not recognize the extension,
494 it will treat the file as C; this is the most generic mode.
496 \&\fINote:\fR Previous versions of cpp accepted a \fB\-lang\fR option
497 which selected both the language and the standards conformance level.
498 This option has been removed, because it conflicts with the \fB\-l\fR
500 .IP "\fB\-std=\fR\fIstandard\fR" 4
501 .IX Item "-std=standard"
506 Specify the standard to which the code should conform. Currently \s-1CPP\s0
507 knows about C and \*(C+ standards; others may be added in the future.
512 .ie n .IP """iso9899:1990""" 4
513 .el .IP "\f(CWiso9899:1990\fR" 4
514 .IX Item "iso9899:1990"
516 .ie n .IP """c89""" 4
517 .el .IP "\f(CWc89\fR" 4
520 The \s-1ISO\s0 C standard from 1990. \fBc89\fR is the customary shorthand for
521 this version of the standard.
523 The \fB\-ansi\fR option is equivalent to \fB\-std=c89\fR.
524 .ie n .IP """iso9899:199409""" 4
525 .el .IP "\f(CWiso9899:199409\fR" 4
526 .IX Item "iso9899:199409"
527 The 1990 C standard, as amended in 1994.
528 .ie n .IP """iso9899:1999""" 4
529 .el .IP "\f(CWiso9899:1999\fR" 4
530 .IX Item "iso9899:1999"
532 .ie n .IP """c99""" 4
533 .el .IP "\f(CWc99\fR" 4
535 .ie n .IP """iso9899:199x""" 4
536 .el .IP "\f(CWiso9899:199x\fR" 4
537 .IX Item "iso9899:199x"
538 .ie n .IP """c9x""" 4
539 .el .IP "\f(CWc9x\fR" 4
542 The revised \s-1ISO\s0 C standard, published in December 1999. Before
543 publication, this was known as C9X.
544 .ie n .IP """gnu89""" 4
545 .el .IP "\f(CWgnu89\fR" 4
547 The 1990 C standard plus \s-1GNU\s0 extensions. This is the default.
548 .ie n .IP """gnu99""" 4
549 .el .IP "\f(CWgnu99\fR" 4
552 .ie n .IP """gnu9x""" 4
553 .el .IP "\f(CWgnu9x\fR" 4
556 The 1999 C standard plus \s-1GNU\s0 extensions.
557 .ie n .IP """c++98""" 4
558 .el .IP "\f(CWc++98\fR" 4
560 The 1998 \s-1ISO\s0 \*(C+ standard plus amendments.
561 .ie n .IP """gnu++98""" 4
562 .el .IP "\f(CWgnu++98\fR" 4
564 The same as \fB\-std=c++98\fR plus \s-1GNU\s0 extensions. This is the
565 default for \*(C+ code.
571 Split the include path. Any directories specified with \fB\-I\fR
572 options before \fB\-I\-\fR are searched only for headers requested with
573 \&\f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR; they are not searched for
574 \&\f(CW\*(C`#include\ <\f(CIfile\f(CW>\*(C'\fR. If additional directories are
575 specified with \fB\-I\fR options after the \fB\-I\-\fR, those
576 directories are searched for all \fB#include\fR directives.
578 In addition, \fB\-I\-\fR inhibits the use of the directory of the current
579 file directory as the first search directory for \f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR.
581 This option has been deprecated.
582 .IP "\fB\-nostdinc\fR" 4
584 Do not search the standard system directories for header files.
585 Only the directories you have specified with \fB\-I\fR options
586 (and the directory of the current file, if appropriate) are searched.
587 .IP "\fB\-nostdinc++\fR" 4
588 .IX Item "-nostdinc++"
589 Do not search for header files in the \*(C+\-specific standard directories,
590 but do still search the other standard directories. (This option is
591 used when building the \*(C+ library.)
592 .IP "\fB\-include\fR \fIfile\fR" 4
593 .IX Item "-include file"
594 Process \fIfile\fR as if \f(CW\*(C`#include "file"\*(C'\fR appeared as the first
595 line of the primary source file. However, the first directory searched
596 for \fIfile\fR is the preprocessor's working directory \fIinstead of\fR
597 the directory containing the main source file. If not found there, it
598 is searched for in the remainder of the \f(CW\*(C`#include "..."\*(C'\fR search
601 If multiple \fB\-include\fR options are given, the files are included
602 in the order they appear on the command line.
603 .IP "\fB\-imacros\fR \fIfile\fR" 4
604 .IX Item "-imacros file"
605 Exactly like \fB\-include\fR, except that any output produced by
606 scanning \fIfile\fR is thrown away. Macros it defines remain defined.
607 This allows you to acquire all the macros from a header without also
608 processing its declarations.
610 All files specified by \fB\-imacros\fR are processed before all files
611 specified by \fB\-include\fR.
612 .IP "\fB\-idirafter\fR \fIdir\fR" 4
613 .IX Item "-idirafter dir"
614 Search \fIdir\fR for header files, but do it \fIafter\fR all
615 directories specified with \fB\-I\fR and the standard system directories
616 have been exhausted. \fIdir\fR is treated as a system include directory.
617 .IP "\fB\-iprefix\fR \fIprefix\fR" 4
618 .IX Item "-iprefix prefix"
619 Specify \fIprefix\fR as the prefix for subsequent \fB\-iwithprefix\fR
620 options. If the prefix represents a directory, you should include the
622 .IP "\fB\-iwithprefix\fR \fIdir\fR" 4
623 .IX Item "-iwithprefix dir"
625 .IP "\fB\-iwithprefixbefore\fR \fIdir\fR" 4
626 .IX Item "-iwithprefixbefore dir"
628 Append \fIdir\fR to the prefix specified previously with
629 \&\fB\-iprefix\fR, and add the resulting directory to the include search
630 path. \fB\-iwithprefixbefore\fR puts it in the same place \fB\-I\fR
631 would; \fB\-iwithprefix\fR puts it where \fB\-idirafter\fR would.
632 .IP "\fB\-isysroot\fR \fIdir\fR" 4
633 .IX Item "-isysroot dir"
634 This option is like the \fB\-\-sysroot\fR option, but applies only to
635 header files. See the \fB\-\-sysroot\fR option for more information.
636 .IP "\fB\-imultilib\fR \fIdir\fR" 4
637 .IX Item "-imultilib dir"
638 Use \fIdir\fR as a subdirectory of the directory containing
639 target-specific \*(C+ headers.
640 .IP "\fB\-isystem\fR \fIdir\fR" 4
641 .IX Item "-isystem dir"
642 Search \fIdir\fR for header files, after all directories specified by
643 \&\fB\-I\fR but before the standard system directories. Mark it
644 as a system directory, so that it gets the same special treatment as
645 is applied to the standard system directories.
646 .IP "\fB\-iquote\fR \fIdir\fR" 4
647 .IX Item "-iquote dir"
648 Search \fIdir\fR only for header files requested with
649 \&\f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR; they are not searched for
650 \&\f(CW\*(C`#include\ <\f(CIfile\f(CW>\*(C'\fR, before all directories specified by
651 \&\fB\-I\fR and before the standard system directories.
652 .IP "\fB\-fdollars\-in\-identifiers\fR" 4
653 .IX Item "-fdollars-in-identifiers"
654 Accept \fB$\fR in identifiers.
655 .IP "\fB\-fextended\-identifiers\fR" 4
656 .IX Item "-fextended-identifiers"
657 Accept universal character names in identifiers. This option is
658 experimental; in a future version of \s-1GCC\s0, it will be enabled by
659 default for C99 and \*(C+.
660 .IP "\fB\-fpreprocessed\fR" 4
661 .IX Item "-fpreprocessed"
662 Indicate to the preprocessor that the input file has already been
663 preprocessed. This suppresses things like macro expansion, trigraph
664 conversion, escaped newline splicing, and processing of most directives.
665 The preprocessor still recognizes and removes comments, so that you can
666 pass a file preprocessed with \fB\-C\fR to the compiler without
667 problems. In this mode the integrated preprocessor is little more than
668 a tokenizer for the front ends.
670 \&\fB\-fpreprocessed\fR is implicit if the input file has one of the
671 extensions \fB.i\fR, \fB.ii\fR or \fB.mi\fR. These are the
672 extensions that \s-1GCC\s0 uses for preprocessed files created by
673 \&\fB\-save\-temps\fR.
674 .IP "\fB\-ftabstop=\fR\fIwidth\fR" 4
675 .IX Item "-ftabstop=width"
676 Set the distance between tab stops. This helps the preprocessor report
677 correct column numbers in warnings or errors, even if tabs appear on the
678 line. If the value is less than 1 or greater than 100, the option is
679 ignored. The default is 8.
680 .IP "\fB\-fexec\-charset=\fR\fIcharset\fR" 4
681 .IX Item "-fexec-charset=charset"
682 Set the execution character set, used for string and character
683 constants. The default is \s-1UTF\-8\s0. \fIcharset\fR can be any encoding
684 supported by the system's \f(CW\*(C`iconv\*(C'\fR library routine.
685 .IP "\fB\-fwide\-exec\-charset=\fR\fIcharset\fR" 4
686 .IX Item "-fwide-exec-charset=charset"
687 Set the wide execution character set, used for wide string and
688 character constants. The default is \s-1UTF\-32\s0 or \s-1UTF\-16\s0, whichever
689 corresponds to the width of \f(CW\*(C`wchar_t\*(C'\fR. As with
690 \&\fB\-fexec\-charset\fR, \fIcharset\fR can be any encoding supported
691 by the system's \f(CW\*(C`iconv\*(C'\fR library routine; however, you will have
692 problems with encodings that do not fit exactly in \f(CW\*(C`wchar_t\*(C'\fR.
693 .IP "\fB\-finput\-charset=\fR\fIcharset\fR" 4
694 .IX Item "-finput-charset=charset"
695 Set the input character set, used for translation from the character
696 set of the input file to the source character set used by \s-1GCC\s0. If the
697 locale does not specify, or \s-1GCC\s0 cannot get this information from the
698 locale, the default is \s-1UTF\-8\s0. This can be overridden by either the locale
699 or this command line option. Currently the command line option takes
700 precedence if there's a conflict. \fIcharset\fR can be any encoding
701 supported by the system's \f(CW\*(C`iconv\*(C'\fR library routine.
702 .IP "\fB\-fworking\-directory\fR" 4
703 .IX Item "-fworking-directory"
704 Enable generation of linemarkers in the preprocessor output that will
705 let the compiler know the current working directory at the time of
706 preprocessing. When this option is enabled, the preprocessor will
707 emit, after the initial linemarker, a second linemarker with the
708 current working directory followed by two slashes. \s-1GCC\s0 will use this
709 directory, when it's present in the preprocessed input, as the
710 directory emitted as the current working directory in some debugging
711 information formats. This option is implicitly enabled if debugging
712 information is enabled, but this can be inhibited with the negated
713 form \fB\-fno\-working\-directory\fR. If the \fB\-P\fR flag is
714 present in the command line, this option has no effect, since no
715 \&\f(CW\*(C`#line\*(C'\fR directives are emitted whatsoever.
716 .IP "\fB\-fno\-show\-column\fR" 4
717 .IX Item "-fno-show-column"
718 Do not print column numbers in diagnostics. This may be necessary if
719 diagnostics are being scanned by a program that does not understand the
720 column numbers, such as \fBdejagnu\fR.
721 .IP "\fB\-A\fR \fIpredicate\fR\fB=\fR\fIanswer\fR" 4
722 .IX Item "-A predicate=answer"
723 Make an assertion with the predicate \fIpredicate\fR and answer
724 \&\fIanswer\fR. This form is preferred to the older form \fB\-A\fR
725 \&\fIpredicate\fR\fB(\fR\fIanswer\fR\fB)\fR, which is still supported, because
726 it does not use shell special characters.
727 .IP "\fB\-A \-\fR\fIpredicate\fR\fB=\fR\fIanswer\fR" 4
728 .IX Item "-A -predicate=answer"
729 Cancel an assertion with the predicate \fIpredicate\fR and answer
731 .IP "\fB\-dCHARS\fR" 4
733 \&\fI\s-1CHARS\s0\fR is a sequence of one or more of the following characters,
734 and must not be preceded by a space. Other characters are interpreted
735 by the compiler proper, or reserved for future versions of \s-1GCC\s0, and so
736 are silently ignored. If you specify characters whose behavior
737 conflicts, the result is undefined.
741 Instead of the normal output, generate a list of \fB#define\fR
742 directives for all the macros defined during the execution of the
743 preprocessor, including predefined macros. This gives you a way of
744 finding out what is predefined in your version of the preprocessor.
745 Assuming you have no file \fIfoo.h\fR, the command
748 \& touch foo.h; cpp -dM foo.h
751 will show all the predefined macros.
754 Like \fBM\fR except in two respects: it does \fInot\fR include the
755 predefined macros, and it outputs \fIboth\fR the \fB#define\fR
756 directives and the result of preprocessing. Both kinds of output go to
757 the standard output file.
760 Like \fBD\fR, but emit only the macro names, not their expansions.
763 Output \fB#include\fR directives in addition to the result of
770 Inhibit generation of linemarkers in the output from the preprocessor.
771 This might be useful when running the preprocessor on something that is
772 not C code, and will be sent to a program which might be confused by the
776 Do not discard comments. All comments are passed through to the output
777 file, except for comments in processed directives, which are deleted
778 along with the directive.
780 You should be prepared for side effects when using \fB\-C\fR; it
781 causes the preprocessor to treat comments as tokens in their own right.
782 For example, comments appearing at the start of what would be a
783 directive line have the effect of turning that line into an ordinary
784 source line, since the first token on the line is no longer a \fB#\fR.
787 Do not discard comments, including during macro expansion. This is
788 like \fB\-C\fR, except that comments contained within macros are
789 also passed through to the output file where the macro is expanded.
791 In addition to the side-effects of the \fB\-C\fR option, the
792 \&\fB\-CC\fR option causes all \*(C+\-style comments inside a macro
793 to be converted to C\-style comments. This is to prevent later use
794 of that macro from inadvertently commenting out the remainder of
797 The \fB\-CC\fR option is generally used to support lint comments.
798 .IP "\fB\-traditional\-cpp\fR" 4
799 .IX Item "-traditional-cpp"
800 Try to imitate the behavior of old-fashioned C preprocessors, as
801 opposed to \s-1ISO\s0 C preprocessors.
802 .IP "\fB\-trigraphs\fR" 4
803 .IX Item "-trigraphs"
804 Process trigraph sequences.
805 .IP "\fB\-remap\fR" 4
807 Enable special code to work around file systems which only permit very
808 short file names, such as \s-1MS\-DOS\s0.
809 .IP "\fB\-\-help\fR" 4
812 .IP "\fB\-\-target\-help\fR" 4
813 .IX Item "--target-help"
815 Print text describing all the command line options instead of
816 preprocessing anything.
819 Verbose mode. Print out \s-1GNU\s0 \s-1CPP\s0's version number at the beginning of
820 execution, and report the final form of the include path.
823 Print the name of each header file used, in addition to other normal
824 activities. Each name is indented to show how deep in the
825 \&\fB#include\fR stack it is. Precompiled header files are also
826 printed, even if they are found to be invalid; an invalid precompiled
827 header file is printed with \fB...x\fR and a valid one with \fB...!\fR .
828 .IP "\fB\-version\fR" 4
831 .IP "\fB\-\-version\fR" 4
834 Print out \s-1GNU\s0 \s-1CPP\s0's version number. With one dash, proceed to
835 preprocess as normal. With two dashes, exit immediately.
837 .IX Header "ENVIRONMENT"
838 This section describes the environment variables that affect how \s-1CPP\s0
839 operates. You can use them to specify directories or prefixes to use
840 when searching for include files, or to control dependency output.
842 Note that you can also specify places to search using options such as
843 \&\fB\-I\fR, and control dependency output with options like
844 \&\fB\-M\fR. These take precedence over
845 environment variables, which in turn take precedence over the
846 configuration of \s-1GCC\s0.
847 .IP "\fB\s-1CPATH\s0\fR" 4
850 .IP "\fBC_INCLUDE_PATH\fR" 4
851 .IX Item "C_INCLUDE_PATH"
852 .IP "\fB\s-1CPLUS_INCLUDE_PATH\s0\fR" 4
853 .IX Item "CPLUS_INCLUDE_PATH"
855 Each variable's value is a list of directories separated by a special
856 character, much like \fB\s-1PATH\s0\fR, in which to look for header files.
857 The special character, \f(CW\*(C`PATH_SEPARATOR\*(C'\fR, is target-dependent and
858 determined at \s-1GCC\s0 build time. For Microsoft Windows-based targets it is a
859 semicolon, and for almost all other targets it is a colon.
861 \&\fB\s-1CPATH\s0\fR specifies a list of directories to be searched as if
862 specified with \fB\-I\fR, but after any paths given with \fB\-I\fR
863 options on the command line. This environment variable is used
864 regardless of which language is being preprocessed.
866 The remaining environment variables apply only when preprocessing the
867 particular language indicated. Each specifies a list of directories
868 to be searched as if specified with \fB\-isystem\fR, but after any
869 paths given with \fB\-isystem\fR options on the command line.
871 In all these variables, an empty element instructs the compiler to
872 search its current working directory. Empty elements can appear at the
873 beginning or end of a path. For instance, if the value of
874 \&\fB\s-1CPATH\s0\fR is \f(CW\*(C`:/special/include\*(C'\fR, that has the same
875 effect as \fB\-I.\ \-I/special/include\fR.
876 .IP "\fB\s-1DEPENDENCIES_OUTPUT\s0\fR" 4
877 .IX Item "DEPENDENCIES_OUTPUT"
878 If this variable is set, its value specifies how to output
879 dependencies for Make based on the non-system header files processed
880 by the compiler. System header files are ignored in the dependency
883 The value of \fB\s-1DEPENDENCIES_OUTPUT\s0\fR can be just a file name, in
884 which case the Make rules are written to that file, guessing the target
885 name from the source file name. Or the value can have the form
886 \&\fIfile\fR\fB \fR\fItarget\fR, in which case the rules are written to
887 file \fIfile\fR using \fItarget\fR as the target name.
889 In other words, this environment variable is equivalent to combining
890 the options \fB\-MM\fR and \fB\-MF\fR,
891 with an optional \fB\-MT\fR switch too.
892 .IP "\fB\s-1SUNPRO_DEPENDENCIES\s0\fR" 4
893 .IX Item "SUNPRO_DEPENDENCIES"
894 This variable is the same as \fB\s-1DEPENDENCIES_OUTPUT\s0\fR (see above),
895 except that system header files are not ignored, so it implies
896 \&\fB\-M\fR rather than \fB\-MM\fR. However, the dependence on the
897 main input file is omitted.
899 .IX Header "SEE ALSO"
900 \&\fIgpl\fR\|(7), \fIgfdl\fR\|(7), \fIfsf\-funding\fR\|(7),
901 \&\fIgcc\fR\|(1), \fIas\fR\|(1), \fIld\fR\|(1), and the Info entries for \fIcpp\fR, \fIgcc\fR, and
904 .IX Header "COPYRIGHT"
905 Copyright (c) 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996,
906 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
907 Free Software Foundation, Inc.
909 Permission is granted to copy, distribute and/or modify this document
910 under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.1 or
911 any later version published by the Free Software Foundation. A copy of
912 the license is included in the
913 man page \fIgfdl\fR\|(7).
914 This manual contains no Invariant Sections. The Front-Cover Texts are
915 (a) (see below), and the Back-Cover Texts are (b) (see below).
917 (a) The \s-1FSF\s0's Front-Cover Text is:
923 (b) The \s-1FSF\s0's Back-Cover Text is:
926 \& You have freedom to copy and modify this GNU Manual, like GNU
927 \& software. Copies published by the Free Software Foundation raise
928 \& funds for GNU development.
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