1CPP(1) GNU CPP(1)
2
6 cpp - The C Preprocessor
7
9 cpp [-Dmacro[=defn]...] [-Umacro]
10 [-Idir...] [-iquotedir...]
11 [-Wwarn...]
12 [-M|-MM] [-MG] [-MF filename]
13 [-MP] [-MQ target...]
14 [-MT target...]
15 [-P] [-fno-working-directory]
16 [-x language] [-std=standard]
17 infile outfile
18 Only the most useful options are listed here; see below for the
20 remainder.
21
23 The C preprocessor, often known as cpp, is a macro processor that is
24 used automatically by the C compiler to transform your program before
25 compilation. It is called a macro processor because it allows you to
26 define macros, which are brief abbreviations for longer constructs.
27 The C preprocessor is intended to be used only with C, C++, and
29 Objective-C source code. In the past, it has been abused as a general
30 text processor. It will choke on input which does not obey C's lexical
31 rules. For example, apostrophes will be interpreted as the beginning
32 of character constants, and cause errors. Also, you cannot rely on it
33 preserving characteristics of the input which are not significant to
34 C-family languages. If a Makefile is preprocessed, all the hard tabs
35 will be removed, and the Makefile will not work.
36 Having said that, you can often get away with using cpp on things which
38 are not C. Other Algol-ish programming languages are often safe
39 (Pascal, Ada, etc.) So is assembly, with caution. -traditional-cpp
40 mode preserves more white space, and is otherwise more permissive.
41 Many of the problems can be avoided by writing C or C++ style comments
42 instead of native language comments, and keeping macros simple.
43 Wherever possible, you should use a preprocessor geared to the language
45 you are writing in. Modern versions of the GNU assembler have macro
46 facilities. Most high level programming languages have their own
47 conditional compilation and inclusion mechanism. If all else fails,
48 try a true general text processor, such as GNU M4.
49 C preprocessors vary in some details. This manual discusses the GNU C
51 preprocessor, which provides a small superset of the features of ISO
52 Standard C. In its default mode, the GNU C preprocessor does not do a
53 few things required by the standard. These are features which are
54 rarely, if ever, used, and may cause surprising changes to the meaning
55 of a program which does not expect them. To get strict ISO Standard C,
56 you should use the -std=c90, -std=c99 or -std=c11 options, depending on
57 which version of the standard you want. To get all the mandatory
58 diagnostics, you must also use -pedantic.
59 This manual describes the behavior of the ISO preprocessor. To
61 minimize gratuitous differences, where the ISO preprocessor's behavior
62 does not conflict with traditional semantics, the traditional
63 preprocessor should behave the same way. The various differences that
64 do exist are detailed in the section Traditional Mode.
65 For clarity, unless noted otherwise, references to CPP in this manual
67 refer to GNU CPP.
68
70 The C preprocessor expects two file names as arguments, infile and
71 outfile. The preprocessor reads infile together with any other files
72 it specifies with #include. All the output generated by the combined
73 input files is written in outfile.
74 Either infile or outfile may be -, which as infile means to read from
76 standard input and as outfile means to write to standard output. Also,
77 if either file is omitted, it means the same as if - had been specified
78 for that file.
79 Unless otherwise noted, or the option ends in =, all options which take
81 an argument may have that argument appear either immediately after the
82 option, or with a space between option and argument: -Ifoo and -I foo
83 have the same effect.
84 Many options have multi-letter names; therefore multiple single-letter
86 options may not be grouped: -dM is very different from -d -M.
87 -D name
89 Predefine name as a macro, with definition 1.
90 -D name=definition
92 The contents of definition are tokenized and processed as if they
93 appeared during translation phase three in a #define directive. In
94 particular, the definition will be truncated by embedded newline
95 characters.
96 If you are invoking the preprocessor from a shell or shell-like
98 program you may need to use the shell's quoting syntax to protect
99 characters such as spaces that have a meaning in the shell syntax.
100 If you wish to define a function-like macro on the command line,
102 write its argument list with surrounding parentheses before the
103 equals sign (if any). Parentheses are meaningful to most shells,
104 so you will need to quote the option. With sh and csh,
105 -D'name(args...)=definition' works.
106 -D and -U options are processed in the order they are given on the
108 command line. All -imacros file and -include file options are
109 processed after all -D and -U options.
110 -U name
112 Cancel any previous definition of name, either built in or provided
113 with a -D option.
114 -undef
116 Do not predefine any system-specific or GCC-specific macros. The
117 standard predefined macros remain defined.
118 -I dir
120 Add the directory dir to the list of directories to be searched for
121 header files.
122 Directories named by -I are searched before the standard system
124 include directories. If the directory dir is a standard system
125 include directory, the option is ignored to ensure that the default
126 search order for system directories and the special treatment of
127 system headers are not defeated . If dir begins with "=", then the
128 "=" will be replaced by the sysroot prefix; see --sysroot and
129 -isysroot.
130 -o file
132 Write output to file. This is the same as specifying file as the
133 second non-option argument to cpp. gcc has a different
134 interpretation of a second non-option argument, so you must use -o
135 to specify the output file.
136 -Wall
138 Turns on all optional warnings which are desirable for normal code.
139 At present this is -Wcomment, -Wtrigraphs, -Wmultichar and a
140 warning about integer promotion causing a change of sign in "#if"
141 expressions. Note that many of the preprocessor's warnings are on
142 by default and have no options to control them.
143 -Wcomment
145 -Wcomments
146 Warn whenever a comment-start sequence /* appears in a /* comment,
147 or whenever a backslash-newline appears in a // comment. (Both
148 forms have the same effect.)
149 -Wtrigraphs
151 Most trigraphs in comments cannot affect the meaning of the
152 program. However, a trigraph that would form an escaped newline
153 (??/ at the end of a line) can, by changing where the comment
154 begins or ends. Therefore, only trigraphs that would form escaped
155 newlines produce warnings inside a comment.
156 This option is implied by -Wall. If -Wall is not given, this
158 option is still enabled unless trigraphs are enabled. To get
159 trigraph conversion without warnings, but get the other -Wall
160 warnings, use -trigraphs -Wall -Wno-trigraphs.
161 -Wtraditional
163 Warn about certain constructs that behave differently in
164 traditional and ISO C. Also warn about ISO C constructs that have
165 no traditional C equivalent, and problematic constructs which
166 should be avoided.
167 -Wundef
169 Warn whenever an identifier which is not a macro is encountered in
170 an #if directive, outside of defined. Such identifiers are
171 replaced with zero.
172 -Wunused-macros
174 Warn about macros defined in the main file that are unused. A
175 macro is used if it is expanded or tested for existence at least
176 once. The preprocessor will also warn if the macro has not been
177 used at the time it is redefined or undefined.
178 Built-in macros, macros defined on the command line, and macros
180 defined in include files are not warned about.
181 Note: If a macro is actually used, but only used in skipped
183 conditional blocks, then CPP will report it as unused. To avoid
184 the warning in such a case, you might improve the scope of the
185 macro's definition by, for example, moving it into the first
186 skipped block. Alternatively, you could provide a dummy use with
187 something like:
188 #if defined the_macro_causing_the_warning
190 #endif
191 -Wendif-labels
193 Warn whenever an #else or an #endif are followed by text. This
194 usually happens in code of the form
195 #if FOO
197 ...
198 #else FOO
199 ...
200 #endif FOO
201 The second and third "FOO" should be in comments, but often are not
203 in older programs. This warning is on by default.
204 -Werror
206 Make all warnings into hard errors. Source code which triggers
207 warnings will be rejected.
208 -Wsystem-headers
210 Issue warnings for code in system headers. These are normally
211 unhelpful in finding bugs in your own code, therefore suppressed.
212 If you are responsible for the system library, you may want to see
213 them.
214 -w Suppress all warnings, including those which GNU CPP issues by
216 default.
217 -pedantic
219 Issue all the mandatory diagnostics listed in the C standard. Some
220 of them are left out by default, since they trigger frequently on
221 harmless code.
222 -pedantic-errors
224 Issue all the mandatory diagnostics, and make all mandatory
225 diagnostics into errors. This includes mandatory diagnostics that
226 GCC issues without -pedantic but treats as warnings.
227 -M Instead of outputting the result of preprocessing, output a rule
229 suitable for make describing the dependencies of the main source
230 file. The preprocessor outputs one make rule containing the object
231 file name for that source file, a colon, and the names of all the
232 included files, including those coming from -include or -imacros
233 command line options.
234 Unless specified explicitly (with -MT or -MQ), the object file name
236 consists of the name of the source file with any suffix replaced
237 with object file suffix and with any leading directory parts
238 removed. If there are many included files then the rule is split
239 into several lines using \-newline. The rule has no commands.
240 This option does not suppress the preprocessor's debug output, such
242 as -dM. To avoid mixing such debug output with the dependency
243 rules you should explicitly specify the dependency output file with
244 -MF, or use an environment variable like DEPENDENCIES_OUTPUT.
245 Debug output will still be sent to the regular output stream as
246 normal.
247 Passing -M to the driver implies -E, and suppresses warnings with
249 an implicit -w.
250 -MM Like -M but do not mention header files that are found in system
252 header directories, nor header files that are included, directly or
253 indirectly, from such a header.
254 This implies that the choice of angle brackets or double quotes in
256 an #include directive does not in itself determine whether that
257 header will appear in -MM dependency output. This is a slight
258 change in semantics from GCC versions 3.0 and earlier.
259 -MF file
261 When used with -M or -MM, specifies a file to write the
262 dependencies to. If no -MF switch is given the preprocessor sends
263 the rules to the same place it would have sent preprocessed output.
264 When used with the driver options -MD or -MMD, -MF overrides the
266 default dependency output file.
267 -MG In conjunction with an option such as -M requesting dependency
269 generation, -MG assumes missing header files are generated files
270 and adds them to the dependency list without raising an error. The
271 dependency filename is taken directly from the "#include" directive
272 without prepending any path. -MG also suppresses preprocessed
273 output, as a missing header file renders this useless.
274 This feature is used in automatic updating of makefiles.
276 -MP This option instructs CPP to add a phony target for each dependency
278 other than the main file, causing each to depend on nothing. These
279 dummy rules work around errors make gives if you remove header
280 files without updating the Makefile to match.
281 This is typical output:
283 test.o: test.c test.h
285 test.h:
287 -MT target
289 Change the target of the rule emitted by dependency generation. By
290 default CPP takes the name of the main input file, deletes any
291 directory components and any file suffix such as .c, and appends
292 the platform's usual object suffix. The result is the target.
293 An -MT option will set the target to be exactly the string you
295 specify. If you want multiple targets, you can specify them as a
296 single argument to -MT, or use multiple -MT options.
297 For example, -MT '$(objpfx)foo.o' might give
299 $(objpfx)foo.o: foo.c
301 -MQ target
303 Same as -MT, but it quotes any characters which are special to
304 Make. -MQ '$(objpfx)foo.o' gives
305 $$(objpfx)foo.o: foo.c
307 The default target is automatically quoted, as if it were given
309 with -MQ.
310 -MD -MD is equivalent to -M -MF file, except that -E is not implied.
312 The driver determines file based on whether an -o option is given.
313 If it is, the driver uses its argument but with a suffix of .d,
314 otherwise it takes the name of the input file, removes any
315 directory components and suffix, and applies a .d suffix.
316 If -MD is used in conjunction with -E, any -o switch is understood
318 to specify the dependency output file, but if used without -E, each
319 -o is understood to specify a target object file.
320 Since -E is not implied, -MD can be used to generate a dependency
322 output file as a side-effect of the compilation process.
323 -MMD
325 Like -MD except mention only user header files, not system header
326 files.
327 -x c
329 -x c++
330 -x objective-c
331 -x assembler-with-cpp
332 Specify the source language: C, C++, Objective-C, or assembly.
333 This has nothing to do with standards conformance or extensions; it
334 merely selects which base syntax to expect. If you give none of
335 these options, cpp will deduce the language from the extension of
336 the source file: .c, .cc, .m, or .S. Some other common extensions
337 for C++ and assembly are also recognized. If cpp does not
338 recognize the extension, it will treat the file as C; this is the
339 most generic mode.
340 Note: Previous versions of cpp accepted a -lang option which
342 selected both the language and the standards conformance level.
343 This option has been removed, because it conflicts with the -l
344 option.
345 -std=standard
347 -ansi
348 Specify the standard to which the code should conform. Currently
349 CPP knows about C and C++ standards; others may be added in the
350 future.
351 standard may be one of:
353 "c90"
355 "c89"
356 "iso9899:1990"
357 The ISO C standard from 1990. c90 is the customary shorthand
358 for this version of the standard.
359 The -ansi option is equivalent to -std=c90.
361 "iso9899:199409"
363 The 1990 C standard, as amended in 1994.
364 "iso9899:1999"
366 "c99"
367 "iso9899:199x"
368 "c9x"
369 The revised ISO C standard, published in December 1999. Before
370 publication, this was known as C9X.
371 "iso9899:2011"
373 "c11"
374 "c1x"
375 The revised ISO C standard, published in December 2011. Before
376 publication, this was known as C1X.
377 "gnu90"
379 "gnu89"
380 The 1990 C standard plus GNU extensions. This is the default.
381 "gnu99"
383 "gnu9x"
384 The 1999 C standard plus GNU extensions.
385 "gnu11"
387 "gnu1x"
388 The 2011 C standard plus GNU extensions.
389 "c++98"
391 The 1998 ISO C++ standard plus amendments.
392 "gnu++98"
394 The same as -std=c++98 plus GNU extensions. This is the
395 default for C++ code.
396 -I- Split the include path. Any directories specified with -I options
398 before -I- are searched only for headers requested with
399 "#include "file""; they are not searched for "#include <file>". If
400 additional directories are specified with -I options after the -I-,
401 those directories are searched for all #include directives.
402 In addition, -I- inhibits the use of the directory of the current
404 file directory as the first search directory for "#include "file"".
405 This option has been deprecated.
407 -nostdinc
409 Do not search the standard system directories for header files.
410 Only the directories you have specified with -I options (and the
411 directory of the current file, if appropriate) are searched.
412 -nostdinc++
414 Do not search for header files in the C++-specific standard
415 directories, but do still search the other standard directories.
416 (This option is used when building the C++ library.)
417 -include file
419 Process file as if "#include "file"" appeared as the first line of
420 the primary source file. However, the first directory searched for
421 file is the preprocessor's working directory instead of the
422 directory containing the main source file. If not found there, it
423 is searched for in the remainder of the "#include "..."" search
424 chain as normal.
425 If multiple -include options are given, the files are included in
427 the order they appear on the command line.
428 -imacros file
430 Exactly like -include, except that any output produced by scanning
431 file is thrown away. Macros it defines remain defined. This
432 allows you to acquire all the macros from a header without also
433 processing its declarations.
434 All files specified by -imacros are processed before all files
436 specified by -include.
437 -idirafter dir
439 Search dir for header files, but do it after all directories
440 specified with -I and the standard system directories have been
441 exhausted. dir is treated as a system include directory. If dir
442 begins with "=", then the "=" will be replaced by the sysroot
443 prefix; see --sysroot and -isysroot.
444 -iprefix prefix
446 Specify prefix as the prefix for subsequent -iwithprefix options.
447 If the prefix represents a directory, you should include the final
448 /.
449 -iwithprefix dir
451 -iwithprefixbefore dir
452 Append dir to the prefix specified previously with -iprefix, and
453 add the resulting directory to the include search path.
454 -iwithprefixbefore puts it in the same place -I would; -iwithprefix
455 puts it where -idirafter would.
456 -isysroot dir
458 This option is like the --sysroot option, but applies only to
459 header files (except for Darwin targets, where it applies to both
460 header files and libraries). See the --sysroot option for more
461 information.
462 -imultilib dir
464 Use dir as a subdirectory of the directory containing target-
465 specific C++ headers.
466 -isystem dir
468 Search dir for header files, after all directories specified by -I
469 but before the standard system directories. Mark it as a system
470 directory, so that it gets the same special treatment as is applied
471 to the standard system directories.
472 If dir begins with "=", then the "=" will be replaced by the
474 sysroot prefix; see --sysroot and -isysroot.
475 -iquote dir
477 Search dir only for header files requested with "#include "file"";
478 they are not searched for "#include <file>", before all directories
479 specified by -I and before the standard system directories.
480 If dir begins with "=", then the "=" will be replaced by the
482 sysroot prefix; see --sysroot and -isysroot.
483 -fdirectives-only
485 When preprocessing, handle directives, but do not expand macros.
486 The option's behavior depends on the -E and -fpreprocessed options.
488 With -E, preprocessing is limited to the handling of directives
490 such as "#define", "#ifdef", and "#error". Other preprocessor
491 operations, such as macro expansion and trigraph conversion are not
492 performed. In addition, the -dD option is implicitly enabled.
493 With -fpreprocessed, predefinition of command line and most builtin
495 macros is disabled. Macros such as "__LINE__", which are
496 contextually dependent, are handled normally. This enables
497 compilation of files previously preprocessed with "-E
498 -fdirectives-only".
499 With both -E and -fpreprocessed, the rules for -fpreprocessed take
501 precedence. This enables full preprocessing of files previously
502 preprocessed with "-E -fdirectives-only".
503 -fdollars-in-identifiers
505 Accept $ in identifiers.
506 -fextended-identifiers
508 Accept universal character names in identifiers. This option is
509 experimental; in a future version of GCC, it will be enabled by
510 default for C99 and C++.
511 -fno-canonical-system-headers
513 When preprocessing, do not shorten system header paths with
514 canonicalization.
515 -fpreprocessed
517 Indicate to the preprocessor that the input file has already been
518 preprocessed. This suppresses things like macro expansion,
519 trigraph conversion, escaped newline splicing, and processing of
520 most directives. The preprocessor still recognizes and removes
521 comments, so that you can pass a file preprocessed with -C to the
522 compiler without problems. In this mode the integrated
523 preprocessor is little more than a tokenizer for the front ends.
524 -fpreprocessed is implicit if the input file has one of the
526 extensions .i, .ii or .mi. These are the extensions that GCC uses
527 for preprocessed files created by -save-temps.
528 -ftabstop=width
530 Set the distance between tab stops. This helps the preprocessor
531 report correct column numbers in warnings or errors, even if tabs
532 appear on the line. If the value is less than 1 or greater than
533 100, the option is ignored. The default is 8.
534 -fdebug-cpp
536 This option is only useful for debugging GCC. When used with -E,
537 dumps debugging information about location maps. Every token in
538 the output is preceded by the dump of the map its location belongs
539 to. The dump of the map holding the location of a token would be:
540 {"P":F</file/path>;"F":F</includer/path>;"L":<line_num>;"C":<col_num>;"S":<system_header_p>;"M":<map_address>;"E":<macro_expansion_p>,"loc":<location>}
542 When used without -E, this option has no effect.
544 -ftrack-macro-expansion[=level]
546 Track locations of tokens across macro expansions. This allows the
547 compiler to emit diagnostic about the current macro expansion stack
548 when a compilation error occurs in a macro expansion. Using this
549 option makes the preprocessor and the compiler consume more memory.
550 The level parameter can be used to choose the level of precision of
551 token location tracking thus decreasing the memory consumption if
552 necessary. Value 0 of level de-activates this option just as if no
553 -ftrack-macro-expansion was present on the command line. Value 1
554 tracks tokens locations in a degraded mode for the sake of minimal
555 memory overhead. In this mode all tokens resulting from the
556 expansion of an argument of a function-like macro have the same
557 location. Value 2 tracks tokens locations completely. This value is
558 the most memory hungry. When this option is given no argument, the
559 default parameter value is 2.
560 Note that -ftrack-macro-expansion=2 is activated by default.
562 -fexec-charset=charset
564 Set the execution character set, used for string and character
565 constants. The default is UTF-8. charset can be any encoding
566 supported by the system's "iconv" library routine.
567 -fwide-exec-charset=charset
569 Set the wide execution character set, used for wide string and
570 character constants. The default is UTF-32 or UTF-16, whichever
571 corresponds to the width of "wchar_t". As with -fexec-charset,
572 charset can be any encoding supported by the system's "iconv"
573 library routine; however, you will have problems with encodings
574 that do not fit exactly in "wchar_t".
575 -finput-charset=charset
577 Set the input character set, used for translation from the
578 character set of the input file to the source character set used by
579 GCC. If the locale does not specify, or GCC cannot get this
580 information from the locale, the default is UTF-8. This can be
581 overridden by either the locale or this command line option.
582 Currently the command line option takes precedence if there's a
583 conflict. charset can be any encoding supported by the system's
584 "iconv" library routine.
585 -fworking-directory
587 Enable generation of linemarkers in the preprocessor output that
588 will let the compiler know the current working directory at the
589 time of preprocessing. When this option is enabled, the
590 preprocessor will emit, after the initial linemarker, a second
591 linemarker with the current working directory followed by two
592 slashes. GCC will use this directory, when it's present in the
593 preprocessed input, as the directory emitted as the current working
594 directory in some debugging information formats. This option is
595 implicitly enabled if debugging information is enabled, but this
596 can be inhibited with the negated form -fno-working-directory. If
597 the -P flag is present in the command line, this option has no
598 effect, since no "#line" directives are emitted whatsoever.
599 -fno-show-column
601 Do not print column numbers in diagnostics. This may be necessary
602 if diagnostics are being scanned by a program that does not
603 understand the column numbers, such as dejagnu.
604 -A predicate=answer
606 Make an assertion with the predicate predicate and answer answer.
607 This form is preferred to the older form -A predicate(answer),
608 which is still supported, because it does not use shell special
609 characters.
610 -A -predicate=answer
612 Cancel an assertion with the predicate predicate and answer answer.
613 -dCHARS
615 CHARS is a sequence of one or more of the following characters, and
616 must not be preceded by a space. Other characters are interpreted
617 by the compiler proper, or reserved for future versions of GCC, and
618 so are silently ignored. If you specify characters whose behavior
619 conflicts, the result is undefined.
620 M Instead of the normal output, generate a list of #define
622 directives for all the macros defined during the execution of
623 the preprocessor, including predefined macros. This gives you
624 a way of finding out what is predefined in your version of the
625 preprocessor. Assuming you have no file foo.h, the command
626 touch foo.h; cpp -dM foo.h
628 will show all the predefined macros.
630 If you use -dM without the -E option, -dM is interpreted as a
632 synonym for -fdump-rtl-mach.
633 D Like M except in two respects: it does not include the
635 predefined macros, and it outputs both the #define directives
636 and the result of preprocessing. Both kinds of output go to
637 the standard output file.
638 N Like D, but emit only the macro names, not their expansions.
640 I Output #include directives in addition to the result of
642 preprocessing.
643 U Like D except that only macros that are expanded, or whose
645 definedness is tested in preprocessor directives, are output;
646 the output is delayed until the use or test of the macro; and
647 #undef directives are also output for macros tested but
648 undefined at the time.
649 -P Inhibit generation of linemarkers in the output from the
651 preprocessor. This might be useful when running the preprocessor
652 on something that is not C code, and will be sent to a program
653 which might be confused by the linemarkers.
654 -C Do not discard comments. All comments are passed through to the
656 output file, except for comments in processed directives, which are
657 deleted along with the directive.
658 You should be prepared for side effects when using -C; it causes
660 the preprocessor to treat comments as tokens in their own right.
661 For example, comments appearing at the start of what would be a
662 directive line have the effect of turning that line into an
663 ordinary source line, since the first token on the line is no
664 longer a #.
665 -CC Do not discard comments, including during macro expansion. This is
667 like -C, except that comments contained within macros are also
668 passed through to the output file where the macro is expanded.
669 In addition to the side-effects of the -C option, the -CC option
671 causes all C++-style comments inside a macro to be converted to
672 C-style comments. This is to prevent later use of that macro from
673 inadvertently commenting out the remainder of the source line.
674 The -CC option is generally used to support lint comments.
676 -traditional-cpp
678 Try to imitate the behavior of old-fashioned C preprocessors, as
679 opposed to ISO C preprocessors.
680 -trigraphs
682 Process trigraph sequences.
683 -remap
685 Enable special code to work around file systems which only permit
686 very short file names, such as MS-DOS.
687 --help
689 --target-help
690 Print text describing all the command line options instead of
691 preprocessing anything.
692 -v Verbose mode. Print out GNU CPP's version number at the beginning
694 of execution, and report the final form of the include path.
695 -H Print the name of each header file used, in addition to other
697 normal activities. Each name is indented to show how deep in the
698 #include stack it is. Precompiled header files are also printed,
699 even if they are found to be invalid; an invalid precompiled header
700 file is printed with ...x and a valid one with ...! .
701 -version
703 --version
704 Print out GNU CPP's version number. With one dash, proceed to
705 preprocess as normal. With two dashes, exit immediately.
706
708 This section describes the environment variables that affect how CPP
709 operates. You can use them to specify directories or prefixes to use
710 when searching for include files, or to control dependency output.
711 Note that you can also specify places to search using options such as
713 -I, and control dependency output with options like -M. These take
714 precedence over environment variables, which in turn take precedence
715 over the configuration of GCC.
716 CPATH
718 C_INCLUDE_PATH
719 CPLUS_INCLUDE_PATH
720 OBJC_INCLUDE_PATH
721 Each variable's value is a list of directories separated by a
722 special character, much like PATH, in which to look for header
723 files. The special character, "PATH_SEPARATOR", is target-
724 dependent and determined at GCC build time. For Microsoft Windows-
725 based targets it is a semicolon, and for almost all other targets
726 it is a colon.
727 CPATH specifies a list of directories to be searched as if
729 specified with -I, but after any paths given with -I options on the
730 command line. This environment variable is used regardless of
731 which language is being preprocessed.
732 The remaining environment variables apply only when preprocessing
734 the particular language indicated. Each specifies a list of
735 directories to be searched as if specified with -isystem, but after
736 any paths given with -isystem options on the command line.
737 In all these variables, an empty element instructs the compiler to
739 search its current working directory. Empty elements can appear at
740 the beginning or end of a path. For instance, if the value of
741 CPATH is ":/special/include", that has the same effect as
742 -I. -I/special/include.
743 DEPENDENCIES_OUTPUT
745 If this variable is set, its value specifies how to output
746 dependencies for Make based on the non-system header files
747 processed by the compiler. System header files are ignored in the
748 dependency output.
749 The value of DEPENDENCIES_OUTPUT can be just a file name, in which
751 case the Make rules are written to that file, guessing the target
752 name from the source file name. Or the value can have the form
753 file target, in which case the rules are written to file file using
754 target as the target name.
755 In other words, this environment variable is equivalent to
757 combining the options -MM and -MF, with an optional -MT switch too.
758 SUNPRO_DEPENDENCIES
760 This variable is the same as DEPENDENCIES_OUTPUT (see above),
761 except that system header files are not ignored, so it implies -M
762 rather than -MM. However, the dependence on the main input file is
763 omitted.
764
766 gpl(7), gfdl(7), fsf-funding(7), gcc(1), as(1), ld(1), and the Info
767 entries for cpp, gcc, and binutils.
768
770 Copyright (c) 1987-2015 Free Software Foundation, Inc.
771 Permission is granted to copy, distribute and/or modify this document
773 under the terms of the GNU Free Documentation License, Version 1.3 or
774 any later version published by the Free Software Foundation. A copy of
775 the license is included in the man page gfdl(7). This manual contains
776 no Invariant Sections. The Front-Cover Texts are (a) (see below), and
777 the Back-Cover Texts are (b) (see below).
778 (a) The FSF's Front-Cover Text is:
780 A GNU Manual
782 (b) The FSF's Back-Cover Text is:
784 You have freedom to copy and modify this GNU Manual, like GNU
786 software. Copies published by the Free Software Foundation raise
787 funds for GNU development.
788gcc-4.8.5 2015-06-23 CPP(1)