1CPP(1) GNU CPP(1)
2
3
4
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
19 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
28 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
37 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
44 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
50 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=c89 or -std=c99 options, depending on which
57 version of the standard you want. To get all the mandatory
58 diagnostics, you must also use -pedantic.
59
60 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
66 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
75 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
80 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
85 Many options have multi-letter names; therefore multiple single-letter
86 options may not be grouped: -dM is very different from -d -M.
87
88 -D name
89 Predefine name as a macro, with definition 1.
90
91 -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
97 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
101 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
107 -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
111 -U name
112 Cancel any previous definition of name, either built in or provided
113 with a -D option.
114
115 -undef
116 Do not predefine any system-specific or GCC-specific macros. The
117 standard predefined macros remain defined.
118
119 -I dir
120 Add the directory dir to the list of directories to be searched for
121 header files.
122
123 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
131 -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
137 -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
144 -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
150 -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
157 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
162 -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
168 -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
173 -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
179 Built-in macros, macros defined on the command line, and macros
180 defined in include files are not warned about.
181
182 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
189 #if defined the_macro_causing_the_warning
190 #endif
191
192 -Wendif-labels
193 Warn whenever an #else or an #endif are followed by text. This
194 usually happens in code of the form
195
196 #if FOO
197 ...
198 #else FOO
199 ...
200 #endif FOO
201
202 The second and third "FOO" should be in comments, but often are not
203 in older programs. This warning is on by default.
204
205 -Werror
206 Make all warnings into hard errors. Source code which triggers
207 warnings will be rejected.
208
209 -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
215 -w Suppress all warnings, including those which GNU CPP issues by
216 default.
217
218 -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
223 -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
228 -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
235 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
241 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
248 Passing -M to the driver implies -E, and suppresses warnings with
249 an implicit -w.
250
251 -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
255 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
260 -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
265 When used with the driver options -MD or -MMD, -MF overrides the
266 default dependency output file.
267
268 -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
275 This feature is used in automatic updating of makefiles.
276
277 -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
282 This is typical output:
283
284 test.o: test.c test.h
285
286 test.h:
287
288 -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
294 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
298 For example, -MT '$(objpfx)foo.o' might give
299
300 $(objpfx)foo.o: foo.c
301
302 -MQ target
303 Same as -MT, but it quotes any characters which are special to
304 Make. -MQ '$(objpfx)foo.o' gives
305
306 $$(objpfx)foo.o: foo.c
307
308 The default target is automatically quoted, as if it were given
309 with -MQ.
310
311 -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
317 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
321 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
324 -MMD
325 Like -MD except mention only user header files, not system header
326 files.
327
328 -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
341 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
346 -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
352 standard may be one of:
353
354 "iso9899:1990"
355 "c89"
356 The ISO C standard from 1990. c89 is the customary shorthand
357 for this version of the standard.
358
359 The -ansi option is equivalent to -std=c89.
360
361 "iso9899:199409"
362 The 1990 C standard, as amended in 1994.
363
364 "iso9899:1999"
365 "c99"
366 "iso9899:199x"
367 "c9x"
368 The revised ISO C standard, published in December 1999. Before
369 publication, this was known as C9X.
370
371 "gnu89"
372 The 1990 C standard plus GNU extensions. This is the default.
373
374 "gnu99"
375 "gnu9x"
376 The 1999 C standard plus GNU extensions.
377
378 "c++98"
379 The 1998 ISO C++ standard plus amendments.
380
381 "gnu++98"
382 The same as -std=c++98 plus GNU extensions. This is the
383 default for C++ code.
384
385 -I- Split the include path. Any directories specified with -I options
386 before -I- are searched only for headers requested with
387 "#include "file""; they are not searched for "#include <file>". If
388 additional directories are specified with -I options after the -I-,
389 those directories are searched for all #include directives.
390
391 In addition, -I- inhibits the use of the directory of the current
392 file directory as the first search directory for "#include "file"".
393
394 This option has been deprecated.
395
396 -nostdinc
397 Do not search the standard system directories for header files.
398 Only the directories you have specified with -I options (and the
399 directory of the current file, if appropriate) are searched.
400
401 -nostdinc++
402 Do not search for header files in the C++-specific standard
403 directories, but do still search the other standard directories.
404 (This option is used when building the C++ library.)
405
406 -include file
407 Process file as if "#include "file"" appeared as the first line of
408 the primary source file. However, the first directory searched for
409 file is the preprocessor's working directory instead of the
410 directory containing the main source file. If not found there, it
411 is searched for in the remainder of the "#include "..."" search
412 chain as normal.
413
414 If multiple -include options are given, the files are included in
415 the order they appear on the command line.
416
417 -imacros file
418 Exactly like -include, except that any output produced by scanning
419 file is thrown away. Macros it defines remain defined. This
420 allows you to acquire all the macros from a header without also
421 processing its declarations.
422
423 All files specified by -imacros are processed before all files
424 specified by -include.
425
426 -idirafter dir
427 Search dir for header files, but do it after all directories
428 specified with -I and the standard system directories have been
429 exhausted. dir is treated as a system include directory. If dir
430 begins with "=", then the "=" will be replaced by the sysroot
431 prefix; see --sysroot and -isysroot.
432
433 -iprefix prefix
434 Specify prefix as the prefix for subsequent -iwithprefix options.
435 If the prefix represents a directory, you should include the final
436 /.
437
438 -iwithprefix dir
439 -iwithprefixbefore dir
440 Append dir to the prefix specified previously with -iprefix, and
441 add the resulting directory to the include search path.
442 -iwithprefixbefore puts it in the same place -I would; -iwithprefix
443 puts it where -idirafter would.
444
445 -isysroot dir
446 This option is like the --sysroot option, but applies only to
447 header files. See the --sysroot option for more information.
448
449 -imultilib dir
450 Use dir as a subdirectory of the directory containing target-
451 specific C++ headers.
452
453 -isystem dir
454 Search dir for header files, after all directories specified by -I
455 but before the standard system directories. Mark it as a system
456 directory, so that it gets the same special treatment as is applied
457 to the standard system directories.
458
459 If dir begins with "=", then the "=" will be replaced by the
460 sysroot prefix; see --sysroot and -isysroot.
461
462 -iquote dir
463 Search dir only for header files requested with "#include "file"";
464 they are not searched for "#include <file>", before all directories
465 specified by -I and before the standard system directories.
466
467 If dir begins with "=", then the "=" will be replaced by the
468 sysroot prefix; see --sysroot and -isysroot.
469
470 -fdirectives-only
471 When preprocessing, handle directives, but do not expand macros.
472
473 The option's behavior depends on the -E and -fpreprocessed options.
474
475 With -E, preprocessing is limited to the handling of directives
476 such as "#define", "#ifdef", and "#error". Other preprocessor
477 operations, such as macro expansion and trigraph conversion are not
478 performed. In addition, the -dD option is implicitly enabled.
479
480 With -fpreprocessed, predefinition of command line and most builtin
481 macros is disabled. Macros such as "__LINE__", which are
482 contextually dependent, are handled normally. This enables
483 compilation of files previously preprocessed with "-E
484 -fdirectives-only".
485
486 With both -E and -fpreprocessed, the rules for -fpreprocessed take
487 precedence. This enables full preprocessing of files previously
488 preprocessed with "-E -fdirectives-only".
489
490 -fdollars-in-identifiers
491 Accept $ in identifiers.
492
493 -fextended-identifiers
494 Accept universal character names in identifiers. This option is
495 experimental; in a future version of GCC, it will be enabled by
496 default for C99 and C++.
497
498 -fpreprocessed
499 Indicate to the preprocessor that the input file has already been
500 preprocessed. This suppresses things like macro expansion,
501 trigraph conversion, escaped newline splicing, and processing of
502 most directives. The preprocessor still recognizes and removes
503 comments, so that you can pass a file preprocessed with -C to the
504 compiler without problems. In this mode the integrated
505 preprocessor is little more than a tokenizer for the front ends.
506
507 -fpreprocessed is implicit if the input file has one of the
508 extensions .i, .ii or .mi. These are the extensions that GCC uses
509 for preprocessed files created by -save-temps.
510
511 -ftabstop=width
512 Set the distance between tab stops. This helps the preprocessor
513 report correct column numbers in warnings or errors, even if tabs
514 appear on the line. If the value is less than 1 or greater than
515 100, the option is ignored. The default is 8.
516
517 -fexec-charset=charset
518 Set the execution character set, used for string and character
519 constants. The default is UTF-8. charset can be any encoding
520 supported by the system's "iconv" library routine.
521
522 -fwide-exec-charset=charset
523 Set the wide execution character set, used for wide string and
524 character constants. The default is UTF-32 or UTF-16, whichever
525 corresponds to the width of "wchar_t". As with -fexec-charset,
526 charset can be any encoding supported by the system's "iconv"
527 library routine; however, you will have problems with encodings
528 that do not fit exactly in "wchar_t".
529
530 -finput-charset=charset
531 Set the input character set, used for translation from the
532 character set of the input file to the source character set used by
533 GCC. If the locale does not specify, or GCC cannot get this
534 information from the locale, the default is UTF-8. This can be
535 overridden by either the locale or this command line option.
536 Currently the command line option takes precedence if there's a
537 conflict. charset can be any encoding supported by the system's
538 "iconv" library routine.
539
540 -fworking-directory
541 Enable generation of linemarkers in the preprocessor output that
542 will let the compiler know the current working directory at the
543 time of preprocessing. When this option is enabled, the
544 preprocessor will emit, after the initial linemarker, a second
545 linemarker with the current working directory followed by two
546 slashes. GCC will use this directory, when it's present in the
547 preprocessed input, as the directory emitted as the current working
548 directory in some debugging information formats. This option is
549 implicitly enabled if debugging information is enabled, but this
550 can be inhibited with the negated form -fno-working-directory. If
551 the -P flag is present in the command line, this option has no
552 effect, since no "#line" directives are emitted whatsoever.
553
554 -fno-show-column
555 Do not print column numbers in diagnostics. This may be necessary
556 if diagnostics are being scanned by a program that does not
557 understand the column numbers, such as dejagnu.
558
559 -A predicate=answer
560 Make an assertion with the predicate predicate and answer answer.
561 This form is preferred to the older form -A predicate(answer),
562 which is still supported, because it does not use shell special
563 characters.
564
565 -A -predicate=answer
566 Cancel an assertion with the predicate predicate and answer answer.
567
568 -dCHARS
569 CHARS is a sequence of one or more of the following characters, and
570 must not be preceded by a space. Other characters are interpreted
571 by the compiler proper, or reserved for future versions of GCC, and
572 so are silently ignored. If you specify characters whose behavior
573 conflicts, the result is undefined.
574
575 M Instead of the normal output, generate a list of #define
576 directives for all the macros defined during the execution of
577 the preprocessor, including predefined macros. This gives you
578 a way of finding out what is predefined in your version of the
579 preprocessor. Assuming you have no file foo.h, the command
580
581 touch foo.h; cpp -dM foo.h
582
583 will show all the predefined macros.
584
585 If you use -dM without the -E option, -dM is interpreted as a
586 synonym for -fdump-rtl-mach.
587
588 D Like M except in two respects: it does not include the
589 predefined macros, and it outputs both the #define directives
590 and the result of preprocessing. Both kinds of output go to
591 the standard output file.
592
593 N Like D, but emit only the macro names, not their expansions.
594
595 I Output #include directives in addition to the result of
596 preprocessing.
597
598 U Like D except that only macros that are expanded, or whose
599 definedness is tested in preprocessor directives, are output;
600 the output is delayed until the use or test of the macro; and
601 #undef directives are also output for macros tested but
602 undefined at the time.
603
604 -P Inhibit generation of linemarkers in the output from the
605 preprocessor. This might be useful when running the preprocessor
606 on something that is not C code, and will be sent to a program
607 which might be confused by the linemarkers.
608
609 -C Do not discard comments. All comments are passed through to the
610 output file, except for comments in processed directives, which are
611 deleted along with the directive.
612
613 You should be prepared for side effects when using -C; it causes
614 the preprocessor to treat comments as tokens in their own right.
615 For example, comments appearing at the start of what would be a
616 directive line have the effect of turning that line into an
617 ordinary source line, since the first token on the line is no
618 longer a #.
619
620 -CC Do not discard comments, including during macro expansion. This is
621 like -C, except that comments contained within macros are also
622 passed through to the output file where the macro is expanded.
623
624 In addition to the side-effects of the -C option, the -CC option
625 causes all C++-style comments inside a macro to be converted to
626 C-style comments. This is to prevent later use of that macro from
627 inadvertently commenting out the remainder of the source line.
628
629 The -CC option is generally used to support lint comments.
630
631 -traditional-cpp
632 Try to imitate the behavior of old-fashioned C preprocessors, as
633 opposed to ISO C preprocessors.
634
635 -trigraphs
636 Process trigraph sequences.
637
638 -remap
639 Enable special code to work around file systems which only permit
640 very short file names, such as MS-DOS.
641
642 --help
643 --target-help
644 Print text describing all the command line options instead of
645 preprocessing anything.
646
647 -v Verbose mode. Print out GNU CPP's version number at the beginning
648 of execution, and report the final form of the include path.
649
650 -H Print the name of each header file used, in addition to other
651 normal activities. Each name is indented to show how deep in the
652 #include stack it is. Precompiled header files are also printed,
653 even if they are found to be invalid; an invalid precompiled header
654 file is printed with ...x and a valid one with ...! .
655
656 -version
657 --version
658 Print out GNU CPP's version number. With one dash, proceed to
659 preprocess as normal. With two dashes, exit immediately.
660
662 This section describes the environment variables that affect how CPP
663 operates. You can use them to specify directories or prefixes to use
664 when searching for include files, or to control dependency output.
665
666 Note that you can also specify places to search using options such as
667 -I, and control dependency output with options like -M. These take
668 precedence over environment variables, which in turn take precedence
669 over the configuration of GCC.
670
671 CPATH
672 C_INCLUDE_PATH
673 CPLUS_INCLUDE_PATH
674 OBJC_INCLUDE_PATH
675 Each variable's value is a list of directories separated by a
676 special character, much like PATH, in which to look for header
677 files. The special character, "PATH_SEPARATOR", is target-
678 dependent and determined at GCC build time. For Microsoft Windows-
679 based targets it is a semicolon, and for almost all other targets
680 it is a colon.
681
682 CPATH specifies a list of directories to be searched as if
683 specified with -I, but after any paths given with -I options on the
684 command line. This environment variable is used regardless of
685 which language is being preprocessed.
686
687 The remaining environment variables apply only when preprocessing
688 the particular language indicated. Each specifies a list of
689 directories to be searched as if specified with -isystem, but after
690 any paths given with -isystem options on the command line.
691
692 In all these variables, an empty element instructs the compiler to
693 search its current working directory. Empty elements can appear at
694 the beginning or end of a path. For instance, if the value of
695 CPATH is ":/special/include", that has the same effect as
696 -I. -I/special/include.
697
698 DEPENDENCIES_OUTPUT
699 If this variable is set, its value specifies how to output
700 dependencies for Make based on the non-system header files
701 processed by the compiler. System header files are ignored in the
702 dependency output.
703
704 The value of DEPENDENCIES_OUTPUT can be just a file name, in which
705 case the Make rules are written to that file, guessing the target
706 name from the source file name. Or the value can have the form
707 file target, in which case the rules are written to file file using
708 target as the target name.
709
710 In other words, this environment variable is equivalent to
711 combining the options -MM and -MF, with an optional -MT switch too.
712
713 SUNPRO_DEPENDENCIES
714 This variable is the same as DEPENDENCIES_OUTPUT (see above),
715 except that system header files are not ignored, so it implies -M
716 rather than -MM. However, the dependence on the main input file is
717 omitted.
718
720 gpl(7), gfdl(7), fsf-funding(7), gcc(1), as(1), ld(1), and the Info
721 entries for cpp, gcc, and binutils.
722
724 Copyright (c) 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997,
725 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008 Free
726 Software Foundation, Inc.
727
728 Permission is granted to copy, distribute and/or modify this document
729 under the terms of the GNU Free Documentation License, Version 1.2 or
730 any later version published by the Free Software Foundation. A copy of
731 the license is included in the man page gfdl(7). This manual contains
732 no Invariant Sections. The Front-Cover Texts are (a) (see below), and
733 the Back-Cover Texts are (b) (see below).
734
735 (a) The FSF's Front-Cover Text is:
736
737 A GNU Manual
738
739 (b) The FSF's Back-Cover Text is:
740
741 You have freedom to copy and modify this GNU Manual, like GNU
742 software. Copies published by the Free Software Foundation raise
743 funds for GNU development.
744
745
746
747gcc-4.4.7 2012-03-13 CPP(1)