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132 .\" ========================================================================
135 .TH CPP 1 "2009-10-15" "gcc-4.4.2" "GNU"
136 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
137 .\" way too many mistakes in technical documents.
141 cpp \- The C Preprocessor
143 .IX Header "SYNOPSIS"
144 cpp [\fB\-D\fR\fImacro\fR[=\fIdefn\fR]...] [\fB\-U\fR\fImacro\fR]
145 [\fB\-I\fR\fIdir\fR...] [\fB\-iquote\fR\fIdir\fR...]
146 [\fB\-W\fR\fIwarn\fR...]
147 [\fB\-M\fR|\fB\-MM\fR] [\fB\-MG\fR] [\fB\-MF\fR \fIfilename\fR]
148 [\fB\-MP\fR] [\fB\-MQ\fR \fItarget\fR...]
149 [\fB\-MT\fR \fItarget\fR...]
150 [\fB\-P\fR] [\fB\-fno\-working\-directory\fR]
151 [\fB\-x\fR \fIlanguage\fR] [\fB\-std=\fR\fIstandard\fR]
152 \fIinfile\fR \fIoutfile\fR
154 Only the most useful options are listed here; see below for the remainder.
156 .IX Header "DESCRIPTION"
157 The C preprocessor, often known as \fIcpp\fR, is a \fImacro processor\fR
158 that is used automatically by the C compiler to transform your program
159 before compilation. It is called a macro processor because it allows
160 you to define \fImacros\fR, which are brief abbreviations for longer
163 The C preprocessor is intended to be used only with C, \*(C+, and
164 Objective-C source code. In the past, it has been abused as a general
165 text processor. It will choke on input which does not obey C's lexical
166 rules. For example, apostrophes will be interpreted as the beginning of
167 character constants, and cause errors. Also, you cannot rely on it
168 preserving characteristics of the input which are not significant to
169 C\-family languages. If a Makefile is preprocessed, all the hard tabs
170 will be removed, and the Makefile will not work.
172 Having said that, you can often get away with using cpp on things which
173 are not C. Other Algol-ish programming languages are often safe
174 (Pascal, Ada, etc.) So is assembly, with caution. \fB\-traditional\-cpp\fR
175 mode preserves more white space, and is otherwise more permissive. Many
176 of the problems can be avoided by writing C or \*(C+ style comments
177 instead of native language comments, and keeping macros simple.
179 Wherever possible, you should use a preprocessor geared to the language
180 you are writing in. Modern versions of the \s-1GNU\s0 assembler have macro
181 facilities. Most high level programming languages have their own
182 conditional compilation and inclusion mechanism. If all else fails,
183 try a true general text processor, such as \s-1GNU\s0 M4.
185 C preprocessors vary in some details. This manual discusses the \s-1GNU\s0 C
186 preprocessor, which provides a small superset of the features of \s-1ISO\s0
187 Standard C. In its default mode, the \s-1GNU\s0 C preprocessor does not do a
188 few things required by the standard. These are features which are
189 rarely, if ever, used, and may cause surprising changes to the meaning
190 of a program which does not expect them. To get strict \s-1ISO\s0 Standard C,
191 you should use the \fB\-std=c89\fR or \fB\-std=c99\fR options, depending
192 on which version of the standard you want. To get all the mandatory
193 diagnostics, you must also use \fB\-pedantic\fR.
195 This manual describes the behavior of the \s-1ISO\s0 preprocessor. To
196 minimize gratuitous differences, where the \s-1ISO\s0 preprocessor's
197 behavior does not conflict with traditional semantics, the
198 traditional preprocessor should behave the same way. The various
199 differences that do exist are detailed in the section \fBTraditional
202 For clarity, unless noted otherwise, references to \fB\s-1CPP\s0\fR in this
203 manual refer to \s-1GNU\s0 \s-1CPP\s0.
206 The C preprocessor expects two file names as arguments, \fIinfile\fR and
207 \&\fIoutfile\fR. The preprocessor reads \fIinfile\fR together with any
208 other files it specifies with \fB#include\fR. All the output generated
209 by the combined input files is written in \fIoutfile\fR.
211 Either \fIinfile\fR or \fIoutfile\fR may be \fB\-\fR, which as
212 \&\fIinfile\fR means to read from standard input and as \fIoutfile\fR
213 means to write to standard output. Also, if either file is omitted, it
214 means the same as if \fB\-\fR had been specified for that file.
216 Unless otherwise noted, or the option ends in \fB=\fR, all options
217 which take an argument may have that argument appear either immediately
218 after the option, or with a space between option and argument:
219 \&\fB\-Ifoo\fR and \fB\-I foo\fR have the same effect.
221 Many options have multi-letter names; therefore multiple single-letter
222 options may \fInot\fR be grouped: \fB\-dM\fR is very different from
224 .IP "\fB\-D\fR \fIname\fR" 4
226 Predefine \fIname\fR as a macro, with definition \f(CW1\fR.
227 .IP "\fB\-D\fR \fIname\fR\fB=\fR\fIdefinition\fR" 4
228 .IX Item "-D name=definition"
229 The contents of \fIdefinition\fR are tokenized and processed as if
230 they appeared during translation phase three in a \fB#define\fR
231 directive. In particular, the definition will be truncated by
232 embedded newline characters.
234 If you are invoking the preprocessor from a shell or shell-like
235 program you may need to use the shell's quoting syntax to protect
236 characters such as spaces that have a meaning in the shell syntax.
238 If you wish to define a function-like macro on the command line, write
239 its argument list with surrounding parentheses before the equals sign
240 (if any). Parentheses are meaningful to most shells, so you will need
241 to quote the option. With \fBsh\fR and \fBcsh\fR,
242 \&\fB\-D'\fR\fIname\fR\fB(\fR\fIargs...\fR\fB)=\fR\fIdefinition\fR\fB'\fR works.
244 \&\fB\-D\fR and \fB\-U\fR options are processed in the order they
245 are given on the command line. All \fB\-imacros\fR \fIfile\fR and
246 \&\fB\-include\fR \fIfile\fR options are processed after all
247 \&\fB\-D\fR and \fB\-U\fR options.
248 .IP "\fB\-U\fR \fIname\fR" 4
250 Cancel any previous definition of \fIname\fR, either built in or
251 provided with a \fB\-D\fR option.
252 .IP "\fB\-undef\fR" 4
254 Do not predefine any system-specific or GCC-specific macros. The
255 standard predefined macros remain defined.
256 .IP "\fB\-I\fR \fIdir\fR" 4
258 Add the directory \fIdir\fR to the list of directories to be searched
261 Directories named by \fB\-I\fR are searched before the standard
262 system include directories. If the directory \fIdir\fR is a standard
263 system include directory, the option is ignored to ensure that the
264 default search order for system directories and the special treatment
265 of system headers are not defeated
267 If \fIdir\fR begins with \f(CW\*(C`=\*(C'\fR, then the \f(CW\*(C`=\*(C'\fR will be replaced
268 by the sysroot prefix; see \fB\-\-sysroot\fR and \fB\-isysroot\fR.
269 .IP "\fB\-o\fR \fIfile\fR" 4
271 Write output to \fIfile\fR. This is the same as specifying \fIfile\fR
272 as the second non-option argument to \fBcpp\fR. \fBgcc\fR has a
273 different interpretation of a second non-option argument, so you must
274 use \fB\-o\fR to specify the output file.
277 Turns on all optional warnings which are desirable for normal code.
278 At present this is \fB\-Wcomment\fR, \fB\-Wtrigraphs\fR,
279 \&\fB\-Wmultichar\fR and a warning about integer promotion causing a
280 change of sign in \f(CW\*(C`#if\*(C'\fR expressions. Note that many of the
281 preprocessor's warnings are on by default and have no options to
283 .IP "\fB\-Wcomment\fR" 4
286 .IP "\fB\-Wcomments\fR" 4
287 .IX Item "-Wcomments"
289 Warn whenever a comment-start sequence \fB/*\fR appears in a \fB/*\fR
290 comment, or whenever a backslash-newline appears in a \fB//\fR comment.
291 (Both forms have the same effect.)
292 .IP "\fB\-Wtrigraphs\fR" 4
293 .IX Item "-Wtrigraphs"
294 Most trigraphs in comments cannot affect the meaning of the program.
295 However, a trigraph that would form an escaped newline (\fB??/\fR at
296 the end of a line) can, by changing where the comment begins or ends.
297 Therefore, only trigraphs that would form escaped newlines produce
298 warnings inside a comment.
300 This option is implied by \fB\-Wall\fR. If \fB\-Wall\fR is not
301 given, this option is still enabled unless trigraphs are enabled. To
302 get trigraph conversion without warnings, but get the other
303 \&\fB\-Wall\fR warnings, use \fB\-trigraphs \-Wall \-Wno\-trigraphs\fR.
304 .IP "\fB\-Wtraditional\fR" 4
305 .IX Item "-Wtraditional"
306 Warn about certain constructs that behave differently in traditional and
307 \&\s-1ISO\s0 C. Also warn about \s-1ISO\s0 C constructs that have no traditional C
308 equivalent, and problematic constructs which should be avoided.
309 .IP "\fB\-Wundef\fR" 4
311 Warn whenever an identifier which is not a macro is encountered in an
312 \&\fB#if\fR directive, outside of \fBdefined\fR. Such identifiers are
314 .IP "\fB\-Wunused\-macros\fR" 4
315 .IX Item "-Wunused-macros"
316 Warn about macros defined in the main file that are unused. A macro
317 is \fIused\fR if it is expanded or tested for existence at least once.
318 The preprocessor will also warn if the macro has not been used at the
319 time it is redefined or undefined.
321 Built-in macros, macros defined on the command line, and macros
322 defined in include files are not warned about.
324 \&\fINote:\fR If a macro is actually used, but only used in skipped
325 conditional blocks, then \s-1CPP\s0 will report it as unused. To avoid the
326 warning in such a case, you might improve the scope of the macro's
327 definition by, for example, moving it into the first skipped block.
328 Alternatively, you could provide a dummy use with something like:
331 \& #if defined the_macro_causing_the_warning
334 .IP "\fB\-Wendif\-labels\fR" 4
335 .IX Item "-Wendif-labels"
336 Warn whenever an \fB#else\fR or an \fB#endif\fR are followed by text.
337 This usually happens in code of the form
347 The second and third \f(CW\*(C`FOO\*(C'\fR should be in comments, but often are not
348 in older programs. This warning is on by default.
349 .IP "\fB\-Werror\fR" 4
351 Make all warnings into hard errors. Source code which triggers warnings
353 .IP "\fB\-Wsystem\-headers\fR" 4
354 .IX Item "-Wsystem-headers"
355 Issue warnings for code in system headers. These are normally unhelpful
356 in finding bugs in your own code, therefore suppressed. If you are
357 responsible for the system library, you may want to see them.
360 Suppress all warnings, including those which \s-1GNU\s0 \s-1CPP\s0 issues by default.
361 .IP "\fB\-pedantic\fR" 4
363 Issue all the mandatory diagnostics listed in the C standard. Some of
364 them are left out by default, since they trigger frequently on harmless
366 .IP "\fB\-pedantic\-errors\fR" 4
367 .IX Item "-pedantic-errors"
368 Issue all the mandatory diagnostics, and make all mandatory diagnostics
369 into errors. This includes mandatory diagnostics that \s-1GCC\s0 issues
370 without \fB\-pedantic\fR but treats as warnings.
373 Instead of outputting the result of preprocessing, output a rule
374 suitable for \fBmake\fR describing the dependencies of the main
375 source file. The preprocessor outputs one \fBmake\fR rule containing
376 the object file name for that source file, a colon, and the names of all
377 the included files, including those coming from \fB\-include\fR or
378 \&\fB\-imacros\fR command line options.
380 Unless specified explicitly (with \fB\-MT\fR or \fB\-MQ\fR), the
381 object file name consists of the name of the source file with any
382 suffix replaced with object file suffix and with any leading directory
383 parts removed. If there are many included files then the rule is
384 split into several lines using \fB\e\fR\-newline. The rule has no
387 This option does not suppress the preprocessor's debug output, such as
388 \&\fB\-dM\fR. To avoid mixing such debug output with the dependency
389 rules you should explicitly specify the dependency output file with
390 \&\fB\-MF\fR, or use an environment variable like
391 \&\fB\s-1DEPENDENCIES_OUTPUT\s0\fR. Debug output
392 will still be sent to the regular output stream as normal.
394 Passing \fB\-M\fR to the driver implies \fB\-E\fR, and suppresses
395 warnings with an implicit \fB\-w\fR.
398 Like \fB\-M\fR but do not mention header files that are found in
399 system header directories, nor header files that are included,
400 directly or indirectly, from such a header.
402 This implies that the choice of angle brackets or double quotes in an
403 \&\fB#include\fR directive does not in itself determine whether that
404 header will appear in \fB\-MM\fR dependency output. This is a
405 slight change in semantics from \s-1GCC\s0 versions 3.0 and earlier.
406 .IP "\fB\-MF\fR \fIfile\fR" 4
408 When used with \fB\-M\fR or \fB\-MM\fR, specifies a
409 file to write the dependencies to. If no \fB\-MF\fR switch is given
410 the preprocessor sends the rules to the same place it would have sent
413 When used with the driver options \fB\-MD\fR or \fB\-MMD\fR,
414 \&\fB\-MF\fR overrides the default dependency output file.
417 In conjunction with an option such as \fB\-M\fR requesting
418 dependency generation, \fB\-MG\fR assumes missing header files are
419 generated files and adds them to the dependency list without raising
420 an error. The dependency filename is taken directly from the
421 \&\f(CW\*(C`#include\*(C'\fR directive without prepending any path. \fB\-MG\fR
422 also suppresses preprocessed output, as a missing header file renders
425 This feature is used in automatic updating of makefiles.
428 This option instructs \s-1CPP\s0 to add a phony target for each dependency
429 other than the main file, causing each to depend on nothing. These
430 dummy rules work around errors \fBmake\fR gives if you remove header
431 files without updating the \fIMakefile\fR to match.
433 This is typical output:
436 \& test.o: test.c test.h
440 .IP "\fB\-MT\fR \fItarget\fR" 4
441 .IX Item "-MT target"
442 Change the target of the rule emitted by dependency generation. By
443 default \s-1CPP\s0 takes the name of the main input file, deletes any
444 directory components and any file suffix such as \fB.c\fR, and
445 appends the platform's usual object suffix. The result is the target.
447 An \fB\-MT\fR option will set the target to be exactly the string you
448 specify. If you want multiple targets, you can specify them as a single
449 argument to \fB\-MT\fR, or use multiple \fB\-MT\fR options.
451 For example, \fB\-MT\ '$(objpfx)foo.o'\fR might give
454 \& $(objpfx)foo.o: foo.c
456 .IP "\fB\-MQ\fR \fItarget\fR" 4
457 .IX Item "-MQ target"
458 Same as \fB\-MT\fR, but it quotes any characters which are special to
459 Make. \fB\-MQ\ '$(objpfx)foo.o'\fR gives
462 \& $$(objpfx)foo.o: foo.c
465 The default target is automatically quoted, as if it were given with
469 \&\fB\-MD\fR is equivalent to \fB\-M \-MF\fR \fIfile\fR, except that
470 \&\fB\-E\fR is not implied. The driver determines \fIfile\fR based on
471 whether an \fB\-o\fR option is given. If it is, the driver uses its
472 argument but with a suffix of \fI.d\fR, otherwise it takes the name
473 of the input file, removes any directory components and suffix, and
474 applies a \fI.d\fR suffix.
476 If \fB\-MD\fR is used in conjunction with \fB\-E\fR, any
477 \&\fB\-o\fR switch is understood to specify the dependency output file, but if used without \fB\-E\fR, each \fB\-o\fR
478 is understood to specify a target object file.
480 Since \fB\-E\fR is not implied, \fB\-MD\fR can be used to generate
481 a dependency output file as a side-effect of the compilation process.
484 Like \fB\-MD\fR except mention only user header files, not system
489 .IP "\fB\-x c++\fR" 4
491 .IP "\fB\-x objective-c\fR" 4
492 .IX Item "-x objective-c"
493 .IP "\fB\-x assembler-with-cpp\fR" 4
494 .IX Item "-x assembler-with-cpp"
496 Specify the source language: C, \*(C+, Objective-C, or assembly. This has
497 nothing to do with standards conformance or extensions; it merely
498 selects which base syntax to expect. If you give none of these options,
499 cpp will deduce the language from the extension of the source file:
500 \&\fB.c\fR, \fB.cc\fR, \fB.m\fR, or \fB.S\fR. Some other common
501 extensions for \*(C+ and assembly are also recognized. If cpp does not
502 recognize the extension, it will treat the file as C; this is the most
505 \&\fINote:\fR Previous versions of cpp accepted a \fB\-lang\fR option
506 which selected both the language and the standards conformance level.
507 This option has been removed, because it conflicts with the \fB\-l\fR
509 .IP "\fB\-std=\fR\fIstandard\fR" 4
510 .IX Item "-std=standard"
515 Specify the standard to which the code should conform. Currently \s-1CPP\s0
516 knows about C and \*(C+ standards; others may be added in the future.
521 .ie n .IP """iso9899:1990""" 4
522 .el .IP "\f(CWiso9899:1990\fR" 4
523 .IX Item "iso9899:1990"
525 .ie n .IP """c89""" 4
526 .el .IP "\f(CWc89\fR" 4
529 The \s-1ISO\s0 C standard from 1990. \fBc89\fR is the customary shorthand for
530 this version of the standard.
532 The \fB\-ansi\fR option is equivalent to \fB\-std=c89\fR.
533 .ie n .IP """iso9899:199409""" 4
534 .el .IP "\f(CWiso9899:199409\fR" 4
535 .IX Item "iso9899:199409"
536 The 1990 C standard, as amended in 1994.
537 .ie n .IP """iso9899:1999""" 4
538 .el .IP "\f(CWiso9899:1999\fR" 4
539 .IX Item "iso9899:1999"
541 .ie n .IP """c99""" 4
542 .el .IP "\f(CWc99\fR" 4
544 .ie n .IP """iso9899:199x""" 4
545 .el .IP "\f(CWiso9899:199x\fR" 4
546 .IX Item "iso9899:199x"
547 .ie n .IP """c9x""" 4
548 .el .IP "\f(CWc9x\fR" 4
551 The revised \s-1ISO\s0 C standard, published in December 1999. Before
552 publication, this was known as C9X.
553 .ie n .IP """gnu89""" 4
554 .el .IP "\f(CWgnu89\fR" 4
556 The 1990 C standard plus \s-1GNU\s0 extensions. This is the default.
557 .ie n .IP """gnu99""" 4
558 .el .IP "\f(CWgnu99\fR" 4
561 .ie n .IP """gnu9x""" 4
562 .el .IP "\f(CWgnu9x\fR" 4
565 The 1999 C standard plus \s-1GNU\s0 extensions.
566 .ie n .IP """c++98""" 4
567 .el .IP "\f(CWc++98\fR" 4
569 The 1998 \s-1ISO\s0 \*(C+ standard plus amendments.
570 .ie n .IP """gnu++98""" 4
571 .el .IP "\f(CWgnu++98\fR" 4
573 The same as \fB\-std=c++98\fR plus \s-1GNU\s0 extensions. This is the
574 default for \*(C+ code.
580 Split the include path. Any directories specified with \fB\-I\fR
581 options before \fB\-I\-\fR are searched only for headers requested with
582 \&\f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR; they are not searched for
583 \&\f(CW\*(C`#include\ <\f(CIfile\f(CW>\*(C'\fR. If additional directories are
584 specified with \fB\-I\fR options after the \fB\-I\-\fR, those
585 directories are searched for all \fB#include\fR directives.
587 In addition, \fB\-I\-\fR inhibits the use of the directory of the current
588 file directory as the first search directory for \f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR.
590 This option has been deprecated.
591 .IP "\fB\-nostdinc\fR" 4
593 Do not search the standard system directories for header files.
594 Only the directories you have specified with \fB\-I\fR options
595 (and the directory of the current file, if appropriate) are searched.
596 .IP "\fB\-nostdinc++\fR" 4
597 .IX Item "-nostdinc++"
598 Do not search for header files in the \*(C+\-specific standard directories,
599 but do still search the other standard directories. (This option is
600 used when building the \*(C+ library.)
601 .IP "\fB\-include\fR \fIfile\fR" 4
602 .IX Item "-include file"
603 Process \fIfile\fR as if \f(CW\*(C`#include "file"\*(C'\fR appeared as the first
604 line of the primary source file. However, the first directory searched
605 for \fIfile\fR is the preprocessor's working directory \fIinstead of\fR
606 the directory containing the main source file. If not found there, it
607 is searched for in the remainder of the \f(CW\*(C`#include "..."\*(C'\fR search
610 If multiple \fB\-include\fR options are given, the files are included
611 in the order they appear on the command line.
612 .IP "\fB\-imacros\fR \fIfile\fR" 4
613 .IX Item "-imacros file"
614 Exactly like \fB\-include\fR, except that any output produced by
615 scanning \fIfile\fR is thrown away. Macros it defines remain defined.
616 This allows you to acquire all the macros from a header without also
617 processing its declarations.
619 All files specified by \fB\-imacros\fR are processed before all files
620 specified by \fB\-include\fR.
621 .IP "\fB\-idirafter\fR \fIdir\fR" 4
622 .IX Item "-idirafter dir"
623 Search \fIdir\fR for header files, but do it \fIafter\fR all
624 directories specified with \fB\-I\fR and the standard system directories
625 have been exhausted. \fIdir\fR is treated as a system include directory.
626 If \fIdir\fR begins with \f(CW\*(C`=\*(C'\fR, then the \f(CW\*(C`=\*(C'\fR will be replaced
627 by the sysroot prefix; see \fB\-\-sysroot\fR and \fB\-isysroot\fR.
628 .IP "\fB\-iprefix\fR \fIprefix\fR" 4
629 .IX Item "-iprefix prefix"
630 Specify \fIprefix\fR as the prefix for subsequent \fB\-iwithprefix\fR
631 options. If the prefix represents a directory, you should include the
633 .IP "\fB\-iwithprefix\fR \fIdir\fR" 4
634 .IX Item "-iwithprefix dir"
636 .IP "\fB\-iwithprefixbefore\fR \fIdir\fR" 4
637 .IX Item "-iwithprefixbefore dir"
639 Append \fIdir\fR to the prefix specified previously with
640 \&\fB\-iprefix\fR, and add the resulting directory to the include search
641 path. \fB\-iwithprefixbefore\fR puts it in the same place \fB\-I\fR
642 would; \fB\-iwithprefix\fR puts it where \fB\-idirafter\fR would.
643 .IP "\fB\-isysroot\fR \fIdir\fR" 4
644 .IX Item "-isysroot dir"
645 This option is like the \fB\-\-sysroot\fR option, but applies only to
646 header files. See the \fB\-\-sysroot\fR option for more information.
647 .IP "\fB\-imultilib\fR \fIdir\fR" 4
648 .IX Item "-imultilib dir"
649 Use \fIdir\fR as a subdirectory of the directory containing
650 target-specific \*(C+ headers.
651 .IP "\fB\-isystem\fR \fIdir\fR" 4
652 .IX Item "-isystem dir"
653 Search \fIdir\fR for header files, after all directories specified by
654 \&\fB\-I\fR but before the standard system directories. Mark it
655 as a system directory, so that it gets the same special treatment as
656 is applied to the standard system directories.
658 If \fIdir\fR begins with \f(CW\*(C`=\*(C'\fR, then the \f(CW\*(C`=\*(C'\fR will be replaced
659 by the sysroot prefix; see \fB\-\-sysroot\fR and \fB\-isysroot\fR.
660 .IP "\fB\-iquote\fR \fIdir\fR" 4
661 .IX Item "-iquote dir"
662 Search \fIdir\fR only for header files requested with
663 \&\f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR; they are not searched for
664 \&\f(CW\*(C`#include\ <\f(CIfile\f(CW>\*(C'\fR, before all directories specified by
665 \&\fB\-I\fR and before the standard system directories.
667 If \fIdir\fR begins with \f(CW\*(C`=\*(C'\fR, then the \f(CW\*(C`=\*(C'\fR will be replaced
668 by the sysroot prefix; see \fB\-\-sysroot\fR and \fB\-isysroot\fR.
669 .IP "\fB\-fdirectives\-only\fR" 4
670 .IX Item "-fdirectives-only"
671 When preprocessing, handle directives, but do not expand macros.
673 The option's behavior depends on the \fB\-E\fR and \fB\-fpreprocessed\fR
676 With \fB\-E\fR, preprocessing is limited to the handling of directives
677 such as \f(CW\*(C`#define\*(C'\fR, \f(CW\*(C`#ifdef\*(C'\fR, and \f(CW\*(C`#error\*(C'\fR. Other
678 preprocessor operations, such as macro expansion and trigraph
679 conversion are not performed. In addition, the \fB\-dD\fR option is
682 With \fB\-fpreprocessed\fR, predefinition of command line and most
683 builtin macros is disabled. Macros such as \f(CW\*(C`_\|_LINE_\|_\*(C'\fR, which are
684 contextually dependent, are handled normally. This enables compilation of
685 files previously preprocessed with \f(CW\*(C`\-E \-fdirectives\-only\*(C'\fR.
687 With both \fB\-E\fR and \fB\-fpreprocessed\fR, the rules for
688 \&\fB\-fpreprocessed\fR take precedence. This enables full preprocessing of
689 files previously preprocessed with \f(CW\*(C`\-E \-fdirectives\-only\*(C'\fR.
690 .IP "\fB\-fdollars\-in\-identifiers\fR" 4
691 .IX Item "-fdollars-in-identifiers"
692 Accept \fB$\fR in identifiers.
693 .IP "\fB\-fextended\-identifiers\fR" 4
694 .IX Item "-fextended-identifiers"
695 Accept universal character names in identifiers. This option is
696 experimental; in a future version of \s-1GCC\s0, it will be enabled by
697 default for C99 and \*(C+.
698 .IP "\fB\-fpreprocessed\fR" 4
699 .IX Item "-fpreprocessed"
700 Indicate to the preprocessor that the input file has already been
701 preprocessed. This suppresses things like macro expansion, trigraph
702 conversion, escaped newline splicing, and processing of most directives.
703 The preprocessor still recognizes and removes comments, so that you can
704 pass a file preprocessed with \fB\-C\fR to the compiler without
705 problems. In this mode the integrated preprocessor is little more than
706 a tokenizer for the front ends.
708 \&\fB\-fpreprocessed\fR is implicit if the input file has one of the
709 extensions \fB.i\fR, \fB.ii\fR or \fB.mi\fR. These are the
710 extensions that \s-1GCC\s0 uses for preprocessed files created by
711 \&\fB\-save\-temps\fR.
712 .IP "\fB\-ftabstop=\fR\fIwidth\fR" 4
713 .IX Item "-ftabstop=width"
714 Set the distance between tab stops. This helps the preprocessor report
715 correct column numbers in warnings or errors, even if tabs appear on the
716 line. If the value is less than 1 or greater than 100, the option is
717 ignored. The default is 8.
718 .IP "\fB\-fexec\-charset=\fR\fIcharset\fR" 4
719 .IX Item "-fexec-charset=charset"
720 Set the execution character set, used for string and character
721 constants. The default is \s-1UTF\-8\s0. \fIcharset\fR can be any encoding
722 supported by the system's \f(CW\*(C`iconv\*(C'\fR library routine.
723 .IP "\fB\-fwide\-exec\-charset=\fR\fIcharset\fR" 4
724 .IX Item "-fwide-exec-charset=charset"
725 Set the wide execution character set, used for wide string and
726 character constants. The default is \s-1UTF\-32\s0 or \s-1UTF\-16\s0, whichever
727 corresponds to the width of \f(CW\*(C`wchar_t\*(C'\fR. As with
728 \&\fB\-fexec\-charset\fR, \fIcharset\fR can be any encoding supported
729 by the system's \f(CW\*(C`iconv\*(C'\fR library routine; however, you will have
730 problems with encodings that do not fit exactly in \f(CW\*(C`wchar_t\*(C'\fR.
731 .IP "\fB\-finput\-charset=\fR\fIcharset\fR" 4
732 .IX Item "-finput-charset=charset"
733 Set the input character set, used for translation from the character
734 set of the input file to the source character set used by \s-1GCC\s0. If the
735 locale does not specify, or \s-1GCC\s0 cannot get this information from the
736 locale, the default is \s-1UTF\-8\s0. This can be overridden by either the locale
737 or this command line option. Currently the command line option takes
738 precedence if there's a conflict. \fIcharset\fR can be any encoding
739 supported by the system's \f(CW\*(C`iconv\*(C'\fR library routine.
740 .IP "\fB\-fworking\-directory\fR" 4
741 .IX Item "-fworking-directory"
742 Enable generation of linemarkers in the preprocessor output that will
743 let the compiler know the current working directory at the time of
744 preprocessing. When this option is enabled, the preprocessor will
745 emit, after the initial linemarker, a second linemarker with the
746 current working directory followed by two slashes. \s-1GCC\s0 will use this
747 directory, when it's present in the preprocessed input, as the
748 directory emitted as the current working directory in some debugging
749 information formats. This option is implicitly enabled if debugging
750 information is enabled, but this can be inhibited with the negated
751 form \fB\-fno\-working\-directory\fR. If the \fB\-P\fR flag is
752 present in the command line, this option has no effect, since no
753 \&\f(CW\*(C`#line\*(C'\fR directives are emitted whatsoever.
754 .IP "\fB\-fno\-show\-column\fR" 4
755 .IX Item "-fno-show-column"
756 Do not print column numbers in diagnostics. This may be necessary if
757 diagnostics are being scanned by a program that does not understand the
758 column numbers, such as \fBdejagnu\fR.
759 .IP "\fB\-A\fR \fIpredicate\fR\fB=\fR\fIanswer\fR" 4
760 .IX Item "-A predicate=answer"
761 Make an assertion with the predicate \fIpredicate\fR and answer
762 \&\fIanswer\fR. This form is preferred to the older form \fB\-A\fR
763 \&\fIpredicate\fR\fB(\fR\fIanswer\fR\fB)\fR, which is still supported, because
764 it does not use shell special characters.
765 .IP "\fB\-A \-\fR\fIpredicate\fR\fB=\fR\fIanswer\fR" 4
766 .IX Item "-A -predicate=answer"
767 Cancel an assertion with the predicate \fIpredicate\fR and answer
769 .IP "\fB\-dCHARS\fR" 4
771 \&\fI\s-1CHARS\s0\fR is a sequence of one or more of the following characters,
772 and must not be preceded by a space. Other characters are interpreted
773 by the compiler proper, or reserved for future versions of \s-1GCC\s0, and so
774 are silently ignored. If you specify characters whose behavior
775 conflicts, the result is undefined.
779 Instead of the normal output, generate a list of \fB#define\fR
780 directives for all the macros defined during the execution of the
781 preprocessor, including predefined macros. This gives you a way of
782 finding out what is predefined in your version of the preprocessor.
783 Assuming you have no file \fIfoo.h\fR, the command
786 \& touch foo.h; cpp \-dM foo.h
789 will show all the predefined macros.
791 If you use \fB\-dM\fR without the \fB\-E\fR option, \fB\-dM\fR is
792 interpreted as a synonym for \fB\-fdump\-rtl\-mach\fR.
795 Like \fBM\fR except in two respects: it does \fInot\fR include the
796 predefined macros, and it outputs \fIboth\fR the \fB#define\fR
797 directives and the result of preprocessing. Both kinds of output go to
798 the standard output file.
801 Like \fBD\fR, but emit only the macro names, not their expansions.
804 Output \fB#include\fR directives in addition to the result of
808 Like \fBD\fR except that only macros that are expanded, or whose
809 definedness is tested in preprocessor directives, are output; the
810 output is delayed until the use or test of the macro; and
811 \&\fB#undef\fR directives are also output for macros tested but
812 undefined at the time.
818 Inhibit generation of linemarkers in the output from the preprocessor.
819 This might be useful when running the preprocessor on something that is
820 not C code, and will be sent to a program which might be confused by the
824 Do not discard comments. All comments are passed through to the output
825 file, except for comments in processed directives, which are deleted
826 along with the directive.
828 You should be prepared for side effects when using \fB\-C\fR; it
829 causes the preprocessor to treat comments as tokens in their own right.
830 For example, comments appearing at the start of what would be a
831 directive line have the effect of turning that line into an ordinary
832 source line, since the first token on the line is no longer a \fB#\fR.
835 Do not discard comments, including during macro expansion. This is
836 like \fB\-C\fR, except that comments contained within macros are
837 also passed through to the output file where the macro is expanded.
839 In addition to the side-effects of the \fB\-C\fR option, the
840 \&\fB\-CC\fR option causes all \*(C+\-style comments inside a macro
841 to be converted to C\-style comments. This is to prevent later use
842 of that macro from inadvertently commenting out the remainder of
845 The \fB\-CC\fR option is generally used to support lint comments.
846 .IP "\fB\-traditional\-cpp\fR" 4
847 .IX Item "-traditional-cpp"
848 Try to imitate the behavior of old-fashioned C preprocessors, as
849 opposed to \s-1ISO\s0 C preprocessors.
850 .IP "\fB\-trigraphs\fR" 4
851 .IX Item "-trigraphs"
852 Process trigraph sequences.
853 .IP "\fB\-remap\fR" 4
855 Enable special code to work around file systems which only permit very
856 short file names, such as MS-DOS.
857 .IP "\fB\-\-help\fR" 4
860 .IP "\fB\-\-target\-help\fR" 4
861 .IX Item "--target-help"
863 Print text describing all the command line options instead of
864 preprocessing anything.
867 Verbose mode. Print out \s-1GNU\s0 \s-1CPP\s0's version number at the beginning of
868 execution, and report the final form of the include path.
871 Print the name of each header file used, in addition to other normal
872 activities. Each name is indented to show how deep in the
873 \&\fB#include\fR stack it is. Precompiled header files are also
874 printed, even if they are found to be invalid; an invalid precompiled
875 header file is printed with \fB...x\fR and a valid one with \fB...!\fR .
876 .IP "\fB\-version\fR" 4
879 .IP "\fB\-\-version\fR" 4
882 Print out \s-1GNU\s0 \s-1CPP\s0's version number. With one dash, proceed to
883 preprocess as normal. With two dashes, exit immediately.
885 .IX Header "ENVIRONMENT"
886 This section describes the environment variables that affect how \s-1CPP\s0
887 operates. You can use them to specify directories or prefixes to use
888 when searching for include files, or to control dependency output.
890 Note that you can also specify places to search using options such as
891 \&\fB\-I\fR, and control dependency output with options like
892 \&\fB\-M\fR. These take precedence over
893 environment variables, which in turn take precedence over the
894 configuration of \s-1GCC\s0.
895 .IP "\fB\s-1CPATH\s0\fR" 4
898 .IP "\fBC_INCLUDE_PATH\fR" 4
899 .IX Item "C_INCLUDE_PATH"
900 .IP "\fB\s-1CPLUS_INCLUDE_PATH\s0\fR" 4
901 .IX Item "CPLUS_INCLUDE_PATH"
902 .IP "\fB\s-1OBJC_INCLUDE_PATH\s0\fR" 4
903 .IX Item "OBJC_INCLUDE_PATH"
905 Each variable's value is a list of directories separated by a special
906 character, much like \fB\s-1PATH\s0\fR, in which to look for header files.
907 The special character, \f(CW\*(C`PATH_SEPARATOR\*(C'\fR, is target-dependent and
908 determined at \s-1GCC\s0 build time. For Microsoft Windows-based targets it is a
909 semicolon, and for almost all other targets it is a colon.
911 \&\fB\s-1CPATH\s0\fR specifies a list of directories to be searched as if
912 specified with \fB\-I\fR, but after any paths given with \fB\-I\fR
913 options on the command line. This environment variable is used
914 regardless of which language is being preprocessed.
916 The remaining environment variables apply only when preprocessing the
917 particular language indicated. Each specifies a list of directories
918 to be searched as if specified with \fB\-isystem\fR, but after any
919 paths given with \fB\-isystem\fR options on the command line.
921 In all these variables, an empty element instructs the compiler to
922 search its current working directory. Empty elements can appear at the
923 beginning or end of a path. For instance, if the value of
924 \&\fB\s-1CPATH\s0\fR is \f(CW\*(C`:/special/include\*(C'\fR, that has the same
925 effect as \fB\-I.\ \-I/special/include\fR.
926 .IP "\fB\s-1DEPENDENCIES_OUTPUT\s0\fR" 4
927 .IX Item "DEPENDENCIES_OUTPUT"
928 If this variable is set, its value specifies how to output
929 dependencies for Make based on the non-system header files processed
930 by the compiler. System header files are ignored in the dependency
933 The value of \fB\s-1DEPENDENCIES_OUTPUT\s0\fR can be just a file name, in
934 which case the Make rules are written to that file, guessing the target
935 name from the source file name. Or the value can have the form
936 \&\fIfile\fR\fB \fR\fItarget\fR, in which case the rules are written to
937 file \fIfile\fR using \fItarget\fR as the target name.
939 In other words, this environment variable is equivalent to combining
940 the options \fB\-MM\fR and \fB\-MF\fR,
941 with an optional \fB\-MT\fR switch too.
942 .IP "\fB\s-1SUNPRO_DEPENDENCIES\s0\fR" 4
943 .IX Item "SUNPRO_DEPENDENCIES"
944 This variable is the same as \fB\s-1DEPENDENCIES_OUTPUT\s0\fR (see above),
945 except that system header files are not ignored, so it implies
946 \&\fB\-M\fR rather than \fB\-MM\fR. However, the dependence on the
947 main input file is omitted.
949 .IX Header "SEE ALSO"
950 \&\fIgpl\fR\|(7), \fIgfdl\fR\|(7), \fIfsf\-funding\fR\|(7),
951 \&\fIgcc\fR\|(1), \fIas\fR\|(1), \fIld\fR\|(1), and the Info entries for \fIcpp\fR, \fIgcc\fR, and
954 .IX Header "COPYRIGHT"
955 Copyright (c) 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996,
956 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008
957 Free Software Foundation, Inc.
959 Permission is granted to copy, distribute and/or modify this document
960 under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.2 or
961 any later version published by the Free Software Foundation. A copy of
962 the license is included in the
963 man page \fIgfdl\fR\|(7).
964 This manual contains no Invariant Sections. The Front-Cover Texts are
965 (a) (see below), and the Back-Cover Texts are (b) (see below).
967 (a) The \s-1FSF\s0's Front-Cover Text is:
973 (b) The \s-1FSF\s0's Back-Cover Text is:
976 \& You have freedom to copy and modify this GNU Manual, like GNU
977 \& software. Copies published by the Free Software Foundation raise
978 \& funds for GNU development.
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