1CPP(1)                                GNU                               CPP(1)
2
3
4

NAME

6       cpp - The C Preprocessor
7

SYNOPSIS

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

DESCRIPTION

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

OPTIONS

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

ENVIRONMENT

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

SEE ALSO

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)
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