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124 .\" ========================================================================
127 .TH CPP 1 "2010-10-01" "gcc-4.4.5" "GNU"
128 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
129 .\" way too many mistakes in technical documents.
133 cpp \- The C Preprocessor
135 .IX Header "SYNOPSIS"
136 cpp [\fB\-D\fR\fImacro\fR[=\fIdefn\fR]...] [\fB\-U\fR\fImacro\fR]
137 [\fB\-I\fR\fIdir\fR...] [\fB\-iquote\fR\fIdir\fR...]
138 [\fB\-W\fR\fIwarn\fR...]
139 [\fB\-M\fR|\fB\-MM\fR] [\fB\-MG\fR] [\fB\-MF\fR \fIfilename\fR]
140 [\fB\-MP\fR] [\fB\-MQ\fR \fItarget\fR...]
141 [\fB\-MT\fR \fItarget\fR...]
142 [\fB\-P\fR] [\fB\-fno\-working\-directory\fR]
143 [\fB\-x\fR \fIlanguage\fR] [\fB\-std=\fR\fIstandard\fR]
144 \fIinfile\fR \fIoutfile\fR
146 Only the most useful options are listed here; see below for the remainder.
148 .IX Header "DESCRIPTION"
149 The C preprocessor, often known as \fIcpp\fR, is a \fImacro processor\fR
150 that is used automatically by the C compiler to transform your program
151 before compilation. It is called a macro processor because it allows
152 you to define \fImacros\fR, which are brief abbreviations for longer
155 The C preprocessor is intended to be used only with C, \*(C+, and
156 Objective-C source code. In the past, it has been abused as a general
157 text processor. It will choke on input which does not obey C's lexical
158 rules. For example, apostrophes will be interpreted as the beginning of
159 character constants, and cause errors. Also, you cannot rely on it
160 preserving characteristics of the input which are not significant to
161 C\-family languages. If a Makefile is preprocessed, all the hard tabs
162 will be removed, and the Makefile will not work.
164 Having said that, you can often get away with using cpp on things which
165 are not C. Other Algol-ish programming languages are often safe
166 (Pascal, Ada, etc.) So is assembly, with caution. \fB\-traditional\-cpp\fR
167 mode preserves more white space, and is otherwise more permissive. Many
168 of the problems can be avoided by writing C or \*(C+ style comments
169 instead of native language comments, and keeping macros simple.
171 Wherever possible, you should use a preprocessor geared to the language
172 you are writing in. Modern versions of the \s-1GNU\s0 assembler have macro
173 facilities. Most high level programming languages have their own
174 conditional compilation and inclusion mechanism. If all else fails,
175 try a true general text processor, such as \s-1GNU\s0 M4.
177 C preprocessors vary in some details. This manual discusses the \s-1GNU\s0 C
178 preprocessor, which provides a small superset of the features of \s-1ISO\s0
179 Standard C. In its default mode, the \s-1GNU\s0 C preprocessor does not do a
180 few things required by the standard. These are features which are
181 rarely, if ever, used, and may cause surprising changes to the meaning
182 of a program which does not expect them. To get strict \s-1ISO\s0 Standard C,
183 you should use the \fB\-std=c89\fR or \fB\-std=c99\fR options, depending
184 on which version of the standard you want. To get all the mandatory
185 diagnostics, you must also use \fB\-pedantic\fR.
187 This manual describes the behavior of the \s-1ISO\s0 preprocessor. To
188 minimize gratuitous differences, where the \s-1ISO\s0 preprocessor's
189 behavior does not conflict with traditional semantics, the
190 traditional preprocessor should behave the same way. The various
191 differences that do exist are detailed in the section \fBTraditional
194 For clarity, unless noted otherwise, references to \fB\s-1CPP\s0\fR in this
195 manual refer to \s-1GNU\s0 \s-1CPP\s0.
198 The C preprocessor expects two file names as arguments, \fIinfile\fR and
199 \&\fIoutfile\fR. The preprocessor reads \fIinfile\fR together with any
200 other files it specifies with \fB#include\fR. All the output generated
201 by the combined input files is written in \fIoutfile\fR.
203 Either \fIinfile\fR or \fIoutfile\fR may be \fB\-\fR, which as
204 \&\fIinfile\fR means to read from standard input and as \fIoutfile\fR
205 means to write to standard output. Also, if either file is omitted, it
206 means the same as if \fB\-\fR had been specified for that file.
208 Unless otherwise noted, or the option ends in \fB=\fR, all options
209 which take an argument may have that argument appear either immediately
210 after the option, or with a space between option and argument:
211 \&\fB\-Ifoo\fR and \fB\-I foo\fR have the same effect.
213 Many options have multi-letter names; therefore multiple single-letter
214 options may \fInot\fR be grouped: \fB\-dM\fR is very different from
216 .IP "\fB\-D\fR \fIname\fR" 4
218 Predefine \fIname\fR as a macro, with definition \f(CW1\fR.
219 .IP "\fB\-D\fR \fIname\fR\fB=\fR\fIdefinition\fR" 4
220 .IX Item "-D name=definition"
221 The contents of \fIdefinition\fR are tokenized and processed as if
222 they appeared during translation phase three in a \fB#define\fR
223 directive. In particular, the definition will be truncated by
224 embedded newline characters.
226 If you are invoking the preprocessor from a shell or shell-like
227 program you may need to use the shell's quoting syntax to protect
228 characters such as spaces that have a meaning in the shell syntax.
230 If you wish to define a function-like macro on the command line, write
231 its argument list with surrounding parentheses before the equals sign
232 (if any). Parentheses are meaningful to most shells, so you will need
233 to quote the option. With \fBsh\fR and \fBcsh\fR,
234 \&\fB\-D'\fR\fIname\fR\fB(\fR\fIargs...\fR\fB)=\fR\fIdefinition\fR\fB'\fR works.
236 \&\fB\-D\fR and \fB\-U\fR options are processed in the order they
237 are given on the command line. All \fB\-imacros\fR \fIfile\fR and
238 \&\fB\-include\fR \fIfile\fR options are processed after all
239 \&\fB\-D\fR and \fB\-U\fR options.
240 .IP "\fB\-U\fR \fIname\fR" 4
242 Cancel any previous definition of \fIname\fR, either built in or
243 provided with a \fB\-D\fR option.
244 .IP "\fB\-undef\fR" 4
246 Do not predefine any system-specific or GCC-specific macros. The
247 standard predefined macros remain defined.
248 .IP "\fB\-I\fR \fIdir\fR" 4
250 Add the directory \fIdir\fR to the list of directories to be searched
253 Directories named by \fB\-I\fR are searched before the standard
254 system include directories. If the directory \fIdir\fR is a standard
255 system include directory, the option is ignored to ensure that the
256 default search order for system directories and the special treatment
257 of system headers are not defeated
259 If \fIdir\fR begins with \f(CW\*(C`=\*(C'\fR, then the \f(CW\*(C`=\*(C'\fR will be replaced
260 by the sysroot prefix; see \fB\-\-sysroot\fR and \fB\-isysroot\fR.
261 .IP "\fB\-o\fR \fIfile\fR" 4
263 Write output to \fIfile\fR. This is the same as specifying \fIfile\fR
264 as the second non-option argument to \fBcpp\fR. \fBgcc\fR has a
265 different interpretation of a second non-option argument, so you must
266 use \fB\-o\fR to specify the output file.
269 Turns on all optional warnings which are desirable for normal code.
270 At present this is \fB\-Wcomment\fR, \fB\-Wtrigraphs\fR,
271 \&\fB\-Wmultichar\fR and a warning about integer promotion causing a
272 change of sign in \f(CW\*(C`#if\*(C'\fR expressions. Note that many of the
273 preprocessor's warnings are on by default and have no options to
275 .IP "\fB\-Wcomment\fR" 4
278 .IP "\fB\-Wcomments\fR" 4
279 .IX Item "-Wcomments"
281 Warn whenever a comment-start sequence \fB/*\fR appears in a \fB/*\fR
282 comment, or whenever a backslash-newline appears in a \fB//\fR comment.
283 (Both forms have the same effect.)
284 .IP "\fB\-Wtrigraphs\fR" 4
285 .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\-Wundef\fR" 4
303 Warn whenever an identifier which is not a macro is encountered in an
304 \&\fB#if\fR directive, outside of \fBdefined\fR. Such identifiers are
306 .IP "\fB\-Wunused\-macros\fR" 4
307 .IX Item "-Wunused-macros"
308 Warn about macros defined in the main file that are unused. A macro
309 is \fIused\fR if it is expanded or tested for existence at least once.
310 The preprocessor will also warn if the macro has not been used at the
311 time it is redefined or undefined.
313 Built-in macros, macros defined on the command line, and macros
314 defined in include files are not warned about.
316 \&\fINote:\fR If a macro is actually used, but only used in skipped
317 conditional blocks, then \s-1CPP\s0 will report it as unused. To avoid the
318 warning in such a case, you might improve the scope of the macro's
319 definition by, for example, moving it into the first skipped block.
320 Alternatively, you could provide a dummy use with something like:
323 \& #if defined the_macro_causing_the_warning
326 .IP "\fB\-Wendif\-labels\fR" 4
327 .IX Item "-Wendif-labels"
328 Warn whenever an \fB#else\fR or an \fB#endif\fR are followed by text.
329 This usually happens in code of the form
339 The second and third \f(CW\*(C`FOO\*(C'\fR should be in comments, but often are not
340 in older programs. This warning is on by default.
341 .IP "\fB\-Werror\fR" 4
343 Make all warnings into hard errors. Source code which triggers warnings
345 .IP "\fB\-Wsystem\-headers\fR" 4
346 .IX Item "-Wsystem-headers"
347 Issue warnings for code in system headers. These are normally unhelpful
348 in finding bugs in your own code, therefore suppressed. If you are
349 responsible for the system library, you may want to see them.
352 Suppress all warnings, including those which \s-1GNU\s0 \s-1CPP\s0 issues by default.
353 .IP "\fB\-pedantic\fR" 4
355 Issue all the mandatory diagnostics listed in the C standard. Some of
356 them are left out by default, since they trigger frequently on harmless
358 .IP "\fB\-pedantic\-errors\fR" 4
359 .IX Item "-pedantic-errors"
360 Issue all the mandatory diagnostics, and make all mandatory diagnostics
361 into errors. This includes mandatory diagnostics that \s-1GCC\s0 issues
362 without \fB\-pedantic\fR but treats as warnings.
365 Instead of outputting the result of preprocessing, output a rule
366 suitable for \fBmake\fR describing the dependencies of the main
367 source file. The preprocessor outputs one \fBmake\fR rule containing
368 the object file name for that source file, a colon, and the names of all
369 the included files, including those coming from \fB\-include\fR or
370 \&\fB\-imacros\fR command line options.
372 Unless specified explicitly (with \fB\-MT\fR or \fB\-MQ\fR), the
373 object file name consists of the name of the source file with any
374 suffix replaced with object file suffix and with any leading directory
375 parts removed. If there are many included files then the rule is
376 split into several lines using \fB\e\fR\-newline. The rule has no
379 This option does not suppress the preprocessor's debug output, such as
380 \&\fB\-dM\fR. To avoid mixing such debug output with the dependency
381 rules you should explicitly specify the dependency output file with
382 \&\fB\-MF\fR, or use an environment variable like
383 \&\fB\s-1DEPENDENCIES_OUTPUT\s0\fR. Debug output
384 will still be sent to the regular output stream as normal.
386 Passing \fB\-M\fR to the driver implies \fB\-E\fR, and suppresses
387 warnings with an implicit \fB\-w\fR.
390 Like \fB\-M\fR but do not mention header files that are found in
391 system header directories, nor header files that are included,
392 directly or indirectly, from such a header.
394 This implies that the choice of angle brackets or double quotes in an
395 \&\fB#include\fR directive does not in itself determine whether that
396 header will appear in \fB\-MM\fR dependency output. This is a
397 slight change in semantics from \s-1GCC\s0 versions 3.0 and earlier.
398 .IP "\fB\-MF\fR \fIfile\fR" 4
400 When used with \fB\-M\fR or \fB\-MM\fR, specifies a
401 file to write the dependencies to. If no \fB\-MF\fR switch is given
402 the preprocessor sends the rules to the same place it would have sent
405 When used with the driver options \fB\-MD\fR or \fB\-MMD\fR,
406 \&\fB\-MF\fR overrides the default dependency output file.
409 In conjunction with an option such as \fB\-M\fR requesting
410 dependency generation, \fB\-MG\fR assumes missing header files are
411 generated files and adds them to the dependency list without raising
412 an error. The dependency filename is taken directly from the
413 \&\f(CW\*(C`#include\*(C'\fR directive without prepending any path. \fB\-MG\fR
414 also suppresses preprocessed output, as a missing header file renders
417 This feature is used in automatic updating of makefiles.
420 This option instructs \s-1CPP\s0 to add a phony target for each dependency
421 other than the main file, causing each to depend on nothing. These
422 dummy rules work around errors \fBmake\fR gives if you remove header
423 files without updating the \fIMakefile\fR to match.
425 This is typical output:
428 \& test.o: test.c test.h
432 .IP "\fB\-MT\fR \fItarget\fR" 4
433 .IX Item "-MT target"
434 Change the target of the rule emitted by dependency generation. By
435 default \s-1CPP\s0 takes the name of the main input file, deletes any
436 directory components and any file suffix such as \fB.c\fR, and
437 appends the platform's usual object suffix. The result is the target.
439 An \fB\-MT\fR option will set the target to be exactly the string you
440 specify. If you want multiple targets, you can specify them as a single
441 argument to \fB\-MT\fR, or use multiple \fB\-MT\fR options.
443 For example, \fB\-MT\ '$(objpfx)foo.o'\fR might give
446 \& $(objpfx)foo.o: foo.c
448 .IP "\fB\-MQ\fR \fItarget\fR" 4
449 .IX Item "-MQ target"
450 Same as \fB\-MT\fR, but it quotes any characters which are special to
451 Make. \fB\-MQ\ '$(objpfx)foo.o'\fR gives
454 \& $$(objpfx)foo.o: foo.c
457 The default target is automatically quoted, as if it were given with
461 \&\fB\-MD\fR is equivalent to \fB\-M \-MF\fR \fIfile\fR, except that
462 \&\fB\-E\fR is not implied. The driver determines \fIfile\fR based on
463 whether an \fB\-o\fR option is given. If it is, the driver uses its
464 argument but with a suffix of \fI.d\fR, otherwise it takes the name
465 of the input file, removes any directory components and suffix, and
466 applies a \fI.d\fR suffix.
468 If \fB\-MD\fR is used in conjunction with \fB\-E\fR, any
469 \&\fB\-o\fR switch is understood to specify the dependency output file, but if used without \fB\-E\fR, each \fB\-o\fR
470 is understood to specify a target object file.
472 Since \fB\-E\fR is not implied, \fB\-MD\fR can be used to generate
473 a dependency output file as a side-effect of the compilation process.
476 Like \fB\-MD\fR except mention only user header files, not system
481 .IP "\fB\-x c++\fR" 4
483 .IP "\fB\-x objective-c\fR" 4
484 .IX Item "-x objective-c"
485 .IP "\fB\-x assembler-with-cpp\fR" 4
486 .IX Item "-x assembler-with-cpp"
488 Specify the source language: C, \*(C+, Objective-C, or assembly. This has
489 nothing to do with standards conformance or extensions; it merely
490 selects which base syntax to expect. If you give none of these options,
491 cpp will deduce the language from the extension of the source file:
492 \&\fB.c\fR, \fB.cc\fR, \fB.m\fR, or \fB.S\fR. Some other common
493 extensions for \*(C+ and assembly are also recognized. If cpp does not
494 recognize the extension, it will treat the file as C; this is the most
497 \&\fINote:\fR Previous versions of cpp accepted a \fB\-lang\fR option
498 which selected both the language and the standards conformance level.
499 This option has been removed, because it conflicts with the \fB\-l\fR
501 .IP "\fB\-std=\fR\fIstandard\fR" 4
502 .IX Item "-std=standard"
507 Specify the standard to which the code should conform. Currently \s-1CPP\s0
508 knows about C and \*(C+ standards; others may be added in the future.
513 .ie n .IP """iso9899:1990""" 4
514 .el .IP "\f(CWiso9899:1990\fR" 4
515 .IX Item "iso9899:1990"
517 .ie n .IP """c89""" 4
518 .el .IP "\f(CWc89\fR" 4
521 The \s-1ISO\s0 C standard from 1990. \fBc89\fR is the customary shorthand for
522 this version of the standard.
524 The \fB\-ansi\fR option is equivalent to \fB\-std=c89\fR.
525 .ie n .IP """iso9899:199409""" 4
526 .el .IP "\f(CWiso9899:199409\fR" 4
527 .IX Item "iso9899:199409"
528 The 1990 C standard, as amended in 1994.
529 .ie n .IP """iso9899:1999""" 4
530 .el .IP "\f(CWiso9899:1999\fR" 4
531 .IX Item "iso9899:1999"
533 .ie n .IP """c99""" 4
534 .el .IP "\f(CWc99\fR" 4
536 .ie n .IP """iso9899:199x""" 4
537 .el .IP "\f(CWiso9899:199x\fR" 4
538 .IX Item "iso9899:199x"
539 .ie n .IP """c9x""" 4
540 .el .IP "\f(CWc9x\fR" 4
543 The revised \s-1ISO\s0 C standard, published in December 1999. Before
544 publication, this was known as C9X.
545 .ie n .IP """gnu89""" 4
546 .el .IP "\f(CWgnu89\fR" 4
548 The 1990 C standard plus \s-1GNU\s0 extensions. This is the default.
549 .ie n .IP """gnu99""" 4
550 .el .IP "\f(CWgnu99\fR" 4
553 .ie n .IP """gnu9x""" 4
554 .el .IP "\f(CWgnu9x\fR" 4
557 The 1999 C standard plus \s-1GNU\s0 extensions.
558 .ie n .IP """c++98""" 4
559 .el .IP "\f(CWc++98\fR" 4
561 The 1998 \s-1ISO\s0 \*(C+ standard plus amendments.
562 .ie n .IP """gnu++98""" 4
563 .el .IP "\f(CWgnu++98\fR" 4
565 The same as \fB\-std=c++98\fR plus \s-1GNU\s0 extensions. This is the
566 default for \*(C+ code.
572 Split the include path. Any directories specified with \fB\-I\fR
573 options before \fB\-I\-\fR are searched only for headers requested with
574 \&\f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR; they are not searched for
575 \&\f(CW\*(C`#include\ <\f(CIfile\f(CW>\*(C'\fR. If additional directories are
576 specified with \fB\-I\fR options after the \fB\-I\-\fR, those
577 directories are searched for all \fB#include\fR directives.
579 In addition, \fB\-I\-\fR inhibits the use of the directory of the current
580 file directory as the first search directory for \f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR.
582 This option has been deprecated.
583 .IP "\fB\-nostdinc\fR" 4
585 Do not search the standard system directories for header files.
586 Only the directories you have specified with \fB\-I\fR options
587 (and the directory of the current file, if appropriate) are searched.
588 .IP "\fB\-nostdinc++\fR" 4
589 .IX Item "-nostdinc++"
590 Do not search for header files in the \*(C+\-specific standard directories,
591 but do still search the other standard directories. (This option is
592 used when building the \*(C+ library.)
593 .IP "\fB\-include\fR \fIfile\fR" 4
594 .IX Item "-include file"
595 Process \fIfile\fR as if \f(CW\*(C`#include "file"\*(C'\fR appeared as the first
596 line of the primary source file. However, the first directory searched
597 for \fIfile\fR is the preprocessor's working directory \fIinstead of\fR
598 the directory containing the main source file. If not found there, it
599 is searched for in the remainder of the \f(CW\*(C`#include "..."\*(C'\fR search
602 If multiple \fB\-include\fR options are given, the files are included
603 in the order they appear on the command line.
604 .IP "\fB\-imacros\fR \fIfile\fR" 4
605 .IX Item "-imacros file"
606 Exactly like \fB\-include\fR, except that any output produced by
607 scanning \fIfile\fR is thrown away. Macros it defines remain defined.
608 This allows you to acquire all the macros from a header without also
609 processing its declarations.
611 All files specified by \fB\-imacros\fR are processed before all files
612 specified by \fB\-include\fR.
613 .IP "\fB\-idirafter\fR \fIdir\fR" 4
614 .IX Item "-idirafter dir"
615 Search \fIdir\fR for header files, but do it \fIafter\fR all
616 directories specified with \fB\-I\fR and the standard system directories
617 have been exhausted. \fIdir\fR is treated as a system include directory.
618 If \fIdir\fR begins with \f(CW\*(C`=\*(C'\fR, then the \f(CW\*(C`=\*(C'\fR will be replaced
619 by the sysroot prefix; see \fB\-\-sysroot\fR and \fB\-isysroot\fR.
620 .IP "\fB\-iprefix\fR \fIprefix\fR" 4
621 .IX Item "-iprefix prefix"
622 Specify \fIprefix\fR as the prefix for subsequent \fB\-iwithprefix\fR
623 options. If the prefix represents a directory, you should include the
625 .IP "\fB\-iwithprefix\fR \fIdir\fR" 4
626 .IX Item "-iwithprefix dir"
628 .IP "\fB\-iwithprefixbefore\fR \fIdir\fR" 4
629 .IX Item "-iwithprefixbefore dir"
631 Append \fIdir\fR to the prefix specified previously with
632 \&\fB\-iprefix\fR, and add the resulting directory to the include search
633 path. \fB\-iwithprefixbefore\fR puts it in the same place \fB\-I\fR
634 would; \fB\-iwithprefix\fR puts it where \fB\-idirafter\fR would.
635 .IP "\fB\-isysroot\fR \fIdir\fR" 4
636 .IX Item "-isysroot dir"
637 This option is like the \fB\-\-sysroot\fR option, but applies only to
638 header files. See the \fB\-\-sysroot\fR option for more information.
639 .IP "\fB\-imultilib\fR \fIdir\fR" 4
640 .IX Item "-imultilib dir"
641 Use \fIdir\fR as a subdirectory of the directory containing
642 target-specific \*(C+ headers.
643 .IP "\fB\-isystem\fR \fIdir\fR" 4
644 .IX Item "-isystem dir"
645 Search \fIdir\fR for header files, after all directories specified by
646 \&\fB\-I\fR but before the standard system directories. Mark it
647 as a system directory, so that it gets the same special treatment as
648 is applied to the standard system directories.
650 If \fIdir\fR begins with \f(CW\*(C`=\*(C'\fR, then the \f(CW\*(C`=\*(C'\fR will be replaced
651 by the sysroot prefix; see \fB\-\-sysroot\fR and \fB\-isysroot\fR.
652 .IP "\fB\-iquote\fR \fIdir\fR" 4
653 .IX Item "-iquote dir"
654 Search \fIdir\fR only for header files requested with
655 \&\f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR; they are not searched for
656 \&\f(CW\*(C`#include\ <\f(CIfile\f(CW>\*(C'\fR, before all directories specified by
657 \&\fB\-I\fR and before the standard system directories.
659 If \fIdir\fR begins with \f(CW\*(C`=\*(C'\fR, then the \f(CW\*(C`=\*(C'\fR will be replaced
660 by the sysroot prefix; see \fB\-\-sysroot\fR and \fB\-isysroot\fR.
661 .IP "\fB\-fdirectives\-only\fR" 4
662 .IX Item "-fdirectives-only"
663 When preprocessing, handle directives, but do not expand macros.
665 The option's behavior depends on the \fB\-E\fR and \fB\-fpreprocessed\fR
668 With \fB\-E\fR, preprocessing is limited to the handling of directives
669 such as \f(CW\*(C`#define\*(C'\fR, \f(CW\*(C`#ifdef\*(C'\fR, and \f(CW\*(C`#error\*(C'\fR. Other
670 preprocessor operations, such as macro expansion and trigraph
671 conversion are not performed. In addition, the \fB\-dD\fR option is
674 With \fB\-fpreprocessed\fR, predefinition of command line and most
675 builtin macros is disabled. Macros such as \f(CW\*(C`_\|_LINE_\|_\*(C'\fR, which are
676 contextually dependent, are handled normally. This enables compilation of
677 files previously preprocessed with \f(CW\*(C`\-E \-fdirectives\-only\*(C'\fR.
679 With both \fB\-E\fR and \fB\-fpreprocessed\fR, the rules for
680 \&\fB\-fpreprocessed\fR take precedence. This enables full preprocessing of
681 files previously preprocessed with \f(CW\*(C`\-E \-fdirectives\-only\*(C'\fR.
682 .IP "\fB\-fdollars\-in\-identifiers\fR" 4
683 .IX Item "-fdollars-in-identifiers"
684 Accept \fB$\fR in identifiers.
685 .IP "\fB\-fextended\-identifiers\fR" 4
686 .IX Item "-fextended-identifiers"
687 Accept universal character names in identifiers. This option is
688 experimental; in a future version of \s-1GCC\s0, it will be enabled by
689 default for C99 and \*(C+.
690 .IP "\fB\-fpreprocessed\fR" 4
691 .IX Item "-fpreprocessed"
692 Indicate to the preprocessor that the input file has already been
693 preprocessed. This suppresses things like macro expansion, trigraph
694 conversion, escaped newline splicing, and processing of most directives.
695 The preprocessor still recognizes and removes comments, so that you can
696 pass a file preprocessed with \fB\-C\fR to the compiler without
697 problems. In this mode the integrated preprocessor is little more than
698 a tokenizer for the front ends.
700 \&\fB\-fpreprocessed\fR is implicit if the input file has one of the
701 extensions \fB.i\fR, \fB.ii\fR or \fB.mi\fR. These are the
702 extensions that \s-1GCC\s0 uses for preprocessed files created by
703 \&\fB\-save\-temps\fR.
704 .IP "\fB\-ftabstop=\fR\fIwidth\fR" 4
705 .IX Item "-ftabstop=width"
706 Set the distance between tab stops. This helps the preprocessor report
707 correct column numbers in warnings or errors, even if tabs appear on the
708 line. If the value is less than 1 or greater than 100, the option is
709 ignored. The default is 8.
710 .IP "\fB\-fexec\-charset=\fR\fIcharset\fR" 4
711 .IX Item "-fexec-charset=charset"
712 Set the execution character set, used for string and character
713 constants. The default is \s-1UTF\-8\s0. \fIcharset\fR can be any encoding
714 supported by the system's \f(CW\*(C`iconv\*(C'\fR library routine.
715 .IP "\fB\-fwide\-exec\-charset=\fR\fIcharset\fR" 4
716 .IX Item "-fwide-exec-charset=charset"
717 Set the wide execution character set, used for wide string and
718 character constants. The default is \s-1UTF\-32\s0 or \s-1UTF\-16\s0, whichever
719 corresponds to the width of \f(CW\*(C`wchar_t\*(C'\fR. As with
720 \&\fB\-fexec\-charset\fR, \fIcharset\fR can be any encoding supported
721 by the system's \f(CW\*(C`iconv\*(C'\fR library routine; however, you will have
722 problems with encodings that do not fit exactly in \f(CW\*(C`wchar_t\*(C'\fR.
723 .IP "\fB\-finput\-charset=\fR\fIcharset\fR" 4
724 .IX Item "-finput-charset=charset"
725 Set the input character set, used for translation from the character
726 set of the input file to the source character set used by \s-1GCC\s0. If the
727 locale does not specify, or \s-1GCC\s0 cannot get this information from the
728 locale, the default is \s-1UTF\-8\s0. This can be overridden by either the locale
729 or this command line option. Currently the command line option takes
730 precedence if there's a conflict. \fIcharset\fR can be any encoding
731 supported by the system's \f(CW\*(C`iconv\*(C'\fR library routine.
732 .IP "\fB\-fworking\-directory\fR" 4
733 .IX Item "-fworking-directory"
734 Enable generation of linemarkers in the preprocessor output that will
735 let the compiler know the current working directory at the time of
736 preprocessing. When this option is enabled, the preprocessor will
737 emit, after the initial linemarker, a second linemarker with the
738 current working directory followed by two slashes. \s-1GCC\s0 will use this
739 directory, when it's present in the preprocessed input, as the
740 directory emitted as the current working directory in some debugging
741 information formats. This option is implicitly enabled if debugging
742 information is enabled, but this can be inhibited with the negated
743 form \fB\-fno\-working\-directory\fR. If the \fB\-P\fR flag is
744 present in the command line, this option has no effect, since no
745 \&\f(CW\*(C`#line\*(C'\fR directives are emitted whatsoever.
746 .IP "\fB\-fno\-show\-column\fR" 4
747 .IX Item "-fno-show-column"
748 Do not print column numbers in diagnostics. This may be necessary if
749 diagnostics are being scanned by a program that does not understand the
750 column numbers, such as \fBdejagnu\fR.
751 .IP "\fB\-A\fR \fIpredicate\fR\fB=\fR\fIanswer\fR" 4
752 .IX Item "-A predicate=answer"
753 Make an assertion with the predicate \fIpredicate\fR and answer
754 \&\fIanswer\fR. This form is preferred to the older form \fB\-A\fR
755 \&\fIpredicate\fR\fB(\fR\fIanswer\fR\fB)\fR, which is still supported, because
756 it does not use shell special characters.
757 .IP "\fB\-A \-\fR\fIpredicate\fR\fB=\fR\fIanswer\fR" 4
758 .IX Item "-A -predicate=answer"
759 Cancel an assertion with the predicate \fIpredicate\fR and answer
761 .IP "\fB\-dCHARS\fR" 4
763 \&\fI\s-1CHARS\s0\fR is a sequence of one or more of the following characters,
764 and must not be preceded by a space. Other characters are interpreted
765 by the compiler proper, or reserved for future versions of \s-1GCC\s0, and so
766 are silently ignored. If you specify characters whose behavior
767 conflicts, the result is undefined.
771 Instead of the normal output, generate a list of \fB#define\fR
772 directives for all the macros defined during the execution of the
773 preprocessor, including predefined macros. This gives you a way of
774 finding out what is predefined in your version of the preprocessor.
775 Assuming you have no file \fIfoo.h\fR, the command
778 \& touch foo.h; cpp \-dM foo.h
781 will show all the predefined macros.
783 If you use \fB\-dM\fR without the \fB\-E\fR option, \fB\-dM\fR is
784 interpreted as a synonym for \fB\-fdump\-rtl\-mach\fR.
787 Like \fBM\fR except in two respects: it does \fInot\fR include the
788 predefined macros, and it outputs \fIboth\fR the \fB#define\fR
789 directives and the result of preprocessing. Both kinds of output go to
790 the standard output file.
793 Like \fBD\fR, but emit only the macro names, not their expansions.
796 Output \fB#include\fR directives in addition to the result of
800 Like \fBD\fR except that only macros that are expanded, or whose
801 definedness is tested in preprocessor directives, are output; the
802 output is delayed until the use or test of the macro; and
803 \&\fB#undef\fR directives are also output for macros tested but
804 undefined at the time.
810 Inhibit generation of linemarkers in the output from the preprocessor.
811 This might be useful when running the preprocessor on something that is
812 not C code, and will be sent to a program which might be confused by the
816 Do not discard comments. All comments are passed through to the output
817 file, except for comments in processed directives, which are deleted
818 along with the directive.
820 You should be prepared for side effects when using \fB\-C\fR; it
821 causes the preprocessor to treat comments as tokens in their own right.
822 For example, comments appearing at the start of what would be a
823 directive line have the effect of turning that line into an ordinary
824 source line, since the first token on the line is no longer a \fB#\fR.
827 Do not discard comments, including during macro expansion. This is
828 like \fB\-C\fR, except that comments contained within macros are
829 also passed through to the output file where the macro is expanded.
831 In addition to the side-effects of the \fB\-C\fR option, the
832 \&\fB\-CC\fR option causes all \*(C+\-style comments inside a macro
833 to be converted to C\-style comments. This is to prevent later use
834 of that macro from inadvertently commenting out the remainder of
837 The \fB\-CC\fR option is generally used to support lint comments.
838 .IP "\fB\-traditional\-cpp\fR" 4
839 .IX Item "-traditional-cpp"
840 Try to imitate the behavior of old-fashioned C preprocessors, as
841 opposed to \s-1ISO\s0 C preprocessors.
842 .IP "\fB\-trigraphs\fR" 4
843 .IX Item "-trigraphs"
844 Process trigraph sequences.
845 .IP "\fB\-remap\fR" 4
847 Enable special code to work around file systems which only permit very
848 short file names, such as MS-DOS.
849 .IP "\fB\-\-help\fR" 4
852 .IP "\fB\-\-target\-help\fR" 4
853 .IX Item "--target-help"
855 Print text describing all the command line options instead of
856 preprocessing anything.
859 Verbose mode. Print out \s-1GNU\s0 \s-1CPP\s0's version number at the beginning of
860 execution, and report the final form of the include path.
863 Print the name of each header file used, in addition to other normal
864 activities. Each name is indented to show how deep in the
865 \&\fB#include\fR stack it is. Precompiled header files are also
866 printed, even if they are found to be invalid; an invalid precompiled
867 header file is printed with \fB...x\fR and a valid one with \fB...!\fR .
868 .IP "\fB\-version\fR" 4
871 .IP "\fB\-\-version\fR" 4
874 Print out \s-1GNU\s0 \s-1CPP\s0's version number. With one dash, proceed to
875 preprocess as normal. With two dashes, exit immediately.
877 .IX Header "ENVIRONMENT"
878 This section describes the environment variables that affect how \s-1CPP\s0
879 operates. You can use them to specify directories or prefixes to use
880 when searching for include files, or to control dependency output.
882 Note that you can also specify places to search using options such as
883 \&\fB\-I\fR, and control dependency output with options like
884 \&\fB\-M\fR. These take precedence over
885 environment variables, which in turn take precedence over the
886 configuration of \s-1GCC\s0.
887 .IP "\fB\s-1CPATH\s0\fR" 4
890 .IP "\fBC_INCLUDE_PATH\fR" 4
891 .IX Item "C_INCLUDE_PATH"
892 .IP "\fB\s-1CPLUS_INCLUDE_PATH\s0\fR" 4
893 .IX Item "CPLUS_INCLUDE_PATH"
894 .IP "\fB\s-1OBJC_INCLUDE_PATH\s0\fR" 4
895 .IX Item "OBJC_INCLUDE_PATH"
897 Each variable's value is a list of directories separated by a special
898 character, much like \fB\s-1PATH\s0\fR, in which to look for header files.
899 The special character, \f(CW\*(C`PATH_SEPARATOR\*(C'\fR, is target-dependent and
900 determined at \s-1GCC\s0 build time. For Microsoft Windows-based targets it is a
901 semicolon, and for almost all other targets it is a colon.
903 \&\fB\s-1CPATH\s0\fR specifies a list of directories to be searched as if
904 specified with \fB\-I\fR, but after any paths given with \fB\-I\fR
905 options on the command line. This environment variable is used
906 regardless of which language is being preprocessed.
908 The remaining environment variables apply only when preprocessing the
909 particular language indicated. Each specifies a list of directories
910 to be searched as if specified with \fB\-isystem\fR, but after any
911 paths given with \fB\-isystem\fR options on the command line.
913 In all these variables, an empty element instructs the compiler to
914 search its current working directory. Empty elements can appear at the
915 beginning or end of a path. For instance, if the value of
916 \&\fB\s-1CPATH\s0\fR is \f(CW\*(C`:/special/include\*(C'\fR, that has the same
917 effect as \fB\-I.\ \-I/special/include\fR.
918 .IP "\fB\s-1DEPENDENCIES_OUTPUT\s0\fR" 4
919 .IX Item "DEPENDENCIES_OUTPUT"
920 If this variable is set, its value specifies how to output
921 dependencies for Make based on the non-system header files processed
922 by the compiler. System header files are ignored in the dependency
925 The value of \fB\s-1DEPENDENCIES_OUTPUT\s0\fR can be just a file name, in
926 which case the Make rules are written to that file, guessing the target
927 name from the source file name. Or the value can have the form
928 \&\fIfile\fR\fB \fR\fItarget\fR, in which case the rules are written to
929 file \fIfile\fR using \fItarget\fR as the target name.
931 In other words, this environment variable is equivalent to combining
932 the options \fB\-MM\fR and \fB\-MF\fR,
933 with an optional \fB\-MT\fR switch too.
934 .IP "\fB\s-1SUNPRO_DEPENDENCIES\s0\fR" 4
935 .IX Item "SUNPRO_DEPENDENCIES"
936 This variable is the same as \fB\s-1DEPENDENCIES_OUTPUT\s0\fR (see above),
937 except that system header files are not ignored, so it implies
938 \&\fB\-M\fR rather than \fB\-MM\fR. However, the dependence on the
939 main input file is omitted.
941 .IX Header "SEE ALSO"
942 \&\fIgpl\fR\|(7), \fIgfdl\fR\|(7), \fIfsf\-funding\fR\|(7),
943 \&\fIgcc\fR\|(1), \fIas\fR\|(1), \fIld\fR\|(1), and the Info entries for \fIcpp\fR, \fIgcc\fR, and
946 .IX Header "COPYRIGHT"
947 Copyright (c) 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996,
948 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008
949 Free Software Foundation, Inc.
951 Permission is granted to copy, distribute and/or modify this document
952 under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.2 or
953 any later version published by the Free Software Foundation. A copy of
954 the license is included in the
955 man page \fIgfdl\fR\|(7).
956 This manual contains no Invariant Sections. The Front-Cover Texts are
957 (a) (see below), and the Back-Cover Texts are (b) (see below).
959 (a) The \s-1FSF\s0's Front-Cover Text is:
965 (b) The \s-1FSF\s0's Back-Cover Text is:
968 \& You have freedom to copy and modify this GNU Manual, like GNU
969 \& software. Copies published by the Free Software Foundation raise
970 \& funds for GNU development.
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