1.\" Automatically generated by Pod::Man v1.37, Pod::Parser v1.14
2.\"
3.\" Standard preamble:
4.\" ========================================================================
5.de Sh \" Subsection heading
6.br
7.if t .Sp
8.ne 5
9.PP
10\fB\\$1\fR
11.PP
12..
13.de Sp \" Vertical space (when we can't use .PP)
14.if t .sp .5v
15.if n .sp
16..
17.de Vb \" Begin verbatim text
18.ft CW
19.nf
20.ne \\$1
21..
22.de Ve \" End verbatim text
23.ft R
24.fi
25..
26.\" Set up some character translations and predefined strings. \*(-- will
27.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
28.\" double quote, and \*(R" will give a right double quote. | will give a
29.\" real vertical bar. \*(C+ will give a nicer C++. Capital omega is used to
30.\" do unbreakable dashes and therefore won't be available. \*(C` and \*(C'
31.\" expand to `' in nroff, nothing in troff, for use with C<>.
32.tr \(*W-|\(bv\*(Tr
33.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
34.ie n \{\
35. ds -- \(*W-
36. ds PI pi
37. if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
38. if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch
39. ds L" ""
40. ds R" ""
41. ds C` ""
42. ds C' ""
43'br\}
44.el\{\
45. ds -- \|\(em\|
46. ds PI \(*p
47. ds L" ``
48. ds R" ''
49'br\}
50.\"
51.\" If the F register is turned on, we'll generate index entries on stderr for
52.\" titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and index
53.\" entries marked with X<> in POD. Of course, you'll have to process the
54.\" output yourself in some meaningful fashion.
55.if \nF \{\
56. de IX
57. tm Index:\\$1\t\\n%\t"\\$2"
58..
59. nr % 0
60. rr F
61.\}
62.\"
63.\" For nroff, turn off justification. Always turn off hyphenation; it makes
64.\" way too many mistakes in technical documents.
65.hy 0
66.if n .na
67.\"
68.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
69.\" Fear. Run. Save yourself. No user-serviceable parts.
70. \" fudge factors for nroff and troff
71.if n \{\
72. ds #H 0
73. ds #V .8m
74. ds #F .3m
75. ds #[ \f1
76. ds #] \fP
77.\}
--- 43 unchanged lines hidden (view full) ---
121. ds d- d\h'-1'\(ga
122. ds D- D\h'-1'\(hy
123. ds th \o'bp'
124. ds Th \o'LP'
125. ds ae ae
126. ds Ae AE
127.\}
128.rm #[ #] #H #V #F C
129.\" ========================================================================
130.\"
131.IX Title "CPP 1"
132.TH CPP 1 "2006-03-06" "gcc-3.4.6" "GNU"
133.SH "NAME"
134cpp \- The C Preprocessor
135.SH "SYNOPSIS"
136.IX Header "SYNOPSIS"
137cpp [\fB\-D\fR\fImacro\fR[=\fIdefn\fR]...] [\fB\-U\fR\fImacro\fR]
138 [\fB\-I\fR\fIdir\fR...] [\fB\-W\fR\fIwarn\fR...]
139 [\fB\-M\fR|\fB\-MM\fR] [\fB\-MG\fR] [\fB\-MF\fR \fIfilename\fR]
140 [\fB\-MP\fR] [\fB\-MQ\fR \fItarget\fR...]
141 [\fB\-MT\fR \fItarget\fR...]
142 [\fB\-P\fR] [\fB\-fno\-working\-directory\fR]
143 [\fB\-x\fR \fIlanguage\fR] [\fB\-std=\fR\fIstandard\fR]
144 \fIinfile\fR \fIoutfile\fR
145.PP
146Only the most useful options are listed here; see below for the remainder.
147.SH "DESCRIPTION"
148.IX Header "DESCRIPTION"
149The C preprocessor, often known as \fIcpp\fR, is a \fImacro processor\fR
150that is used automatically by the C compiler to transform your program
151before compilation. It is called a macro processor because it allows
152you to define \fImacros\fR, which are brief abbreviations for longer
153constructs.
154.PP
155The C preprocessor is intended to be used only with C, \*(C+, and
156Objective-C source code. In the past, it has been abused as a general
157text processor. It will choke on input which does not obey C's lexical
158rules. For example, apostrophes will be interpreted as the beginning of
159character constants, and cause errors. Also, you cannot rely on it
160preserving characteristics of the input which are not significant to
161C\-family languages. If a Makefile is preprocessed, all the hard tabs
162will be removed, and the Makefile will not work.
163.PP
164Having said that, you can often get away with using cpp on things which
165are not C. Other Algol-ish programming languages are often safe
166(Pascal, Ada, etc.) So is assembly, with caution. \fB\-traditional\-cpp\fR
167mode preserves more white space, and is otherwise more permissive. Many
168of the problems can be avoided by writing C or \*(C+ style comments
169instead of native language comments, and keeping macros simple.
170.PP
171Wherever possible, you should use a preprocessor geared to the language
172you are writing in. Modern versions of the \s-1GNU\s0 assembler have macro
173facilities. Most high level programming languages have their own
174conditional compilation and inclusion mechanism. If all else fails,
175try a true general text processor, such as \s-1GNU\s0 M4.
176.PP
177C preprocessors vary in some details. This manual discusses the \s-1GNU\s0 C
178preprocessor, which provides a small superset of the features of \s-1ISO\s0
179Standard C. In its default mode, the \s-1GNU\s0 C preprocessor does not do a
180few things required by the standard. These are features which are
181rarely, if ever, used, and may cause surprising changes to the meaning
182of a program which does not expect them. To get strict \s-1ISO\s0 Standard C,
183you should use the \fB\-std=c89\fR or \fB\-std=c99\fR options, depending
184on which version of the standard you want. To get all the mandatory
185diagnostics, you must also use \fB\-pedantic\fR.
186.PP
187This manual describes the behavior of the \s-1ISO\s0 preprocessor. To
188minimize gratuitous differences, where the \s-1ISO\s0 preprocessor's
189behavior does not conflict with traditional semantics, the
190traditional preprocessor should behave the same way. The various
191differences that do exist are detailed in the section \fBTraditional
192Mode\fR.
193.PP
194For clarity, unless noted otherwise, references to \fB\s-1CPP\s0\fR in this
195manual refer to \s-1GNU\s0 \s-1CPP\s0.
196.SH "OPTIONS"
197.IX Header "OPTIONS"
198The C preprocessor expects two file names as arguments, \fIinfile\fR and
199\&\fIoutfile\fR. The preprocessor reads \fIinfile\fR together with any
200other files it specifies with \fB#include\fR. All the output generated
201by the combined input files is written in \fIoutfile\fR.
202.PP
203Either \fIinfile\fR or \fIoutfile\fR may be \fB\-\fR, which as
204\&\fIinfile\fR means to read from standard input and as \fIoutfile\fR
205means to write to standard output. Also, if either file is omitted, it
206means the same as if \fB\-\fR had been specified for that file.
207.PP
208Unless otherwise noted, or the option ends in \fB=\fR, all options
209which take an argument may have that argument appear either immediately
210after the option, or with a space between option and argument:
211\&\fB\-Ifoo\fR and \fB\-I foo\fR have the same effect.
212.PP
213Many options have multi-letter names; therefore multiple single-letter
214options may \fInot\fR be grouped: \fB\-dM\fR is very different from
215\&\fB\-d\ \-M\fR.
216.IP "\fB\-D\fR \fIname\fR" 4
217.IX Item "-D name"
218Predefine \fIname\fR as a macro, with definition \f(CW1\fR.
219.IP "\fB\-D\fR \fIname\fR\fB=\fR\fIdefinition\fR" 4
220.IX Item "-D name=definition"
221Predefine \fIname\fR as a macro, with definition \fIdefinition\fR.
222The contents of \fIdefinition\fR are tokenized and processed as if
223they appeared during translation phase three in a \fB#define\fR
224directive. In particular, the definition will be truncated by
225embedded newline characters.
226.Sp
227If you are invoking the preprocessor from a shell or shell-like
228program you may need to use the shell's quoting syntax to protect
229characters such as spaces that have a meaning in the shell syntax.
230.Sp
231If you wish to define a function-like macro on the command line, write
232its argument list with surrounding parentheses before the equals sign
233(if any). Parentheses are meaningful to most shells, so you will need
234to quote the option. With \fBsh\fR and \fBcsh\fR,
235\&\fB\-D'\fR\fIname\fR\fB(\fR\fIargs...\fR\fB)=\fR\fIdefinition\fR\fB'\fR works.
236.Sp
237\&\fB\-D\fR and \fB\-U\fR options are processed in the order they
238are given on the command line. All \fB\-imacros\fR \fIfile\fR and
239\&\fB\-include\fR \fIfile\fR options are processed after all
240\&\fB\-D\fR and \fB\-U\fR options.
241.IP "\fB\-U\fR \fIname\fR" 4
242.IX Item "-U name"
243Cancel any previous definition of \fIname\fR, either built in or
244provided with a \fB\-D\fR option.
245.IP "\fB\-undef\fR" 4
246.IX Item "-undef"
247Do not predefine any system-specific or GCC-specific macros. The
248standard predefined macros remain defined.
249.IP "\fB\-I\fR \fIdir\fR" 4
250.IX Item "-I dir"
251Add the directory \fIdir\fR to the list of directories to be searched
252for header files.
253.Sp
254Directories named by \fB\-I\fR are searched before the standard
255system include directories. If the directory \fIdir\fR is a standard
256system include directory, the option is ignored to ensure that the
257default search order for system directories and the special treatment
258of system headers are not defeated
259\&.
260.IP "\fB\-o\fR \fIfile\fR" 4
261.IX Item "-o file"
262Write output to \fIfile\fR. This is the same as specifying \fIfile\fR
263as the second non-option argument to \fBcpp\fR. \fBgcc\fR has a
264different interpretation of a second non-option argument, so you must
265use \fB\-o\fR to specify the output file.
266.IP "\fB\-Wall\fR" 4
267.IX Item "-Wall"
268Turns on all optional warnings which are desirable for normal code.
269At present this is \fB\-Wcomment\fR, \fB\-Wtrigraphs\fR,
270\&\fB\-Wmultichar\fR and a warning about integer promotion causing a
271change of sign in \f(CW\*(C`#if\*(C'\fR expressions. Note that many of the
272preprocessor's warnings are on by default and have no options to
273control them.
274.IP "\fB\-Wcomment\fR" 4
275.IX Item "-Wcomment"
276.PD 0
277.IP "\fB\-Wcomments\fR" 4
278.IX Item "-Wcomments"
279.PD
280Warn whenever a comment-start sequence \fB/*\fR appears in a \fB/*\fR
281comment, or whenever a backslash-newline appears in a \fB//\fR comment.
282(Both forms have the same effect.)
283.IP "\fB\-Wtrigraphs\fR" 4
284.IX Item "-Wtrigraphs"
285@anchor{Wtrigraphs}
286Most trigraphs in comments cannot affect the meaning of the program.
287However, a trigraph that would form an escaped newline (\fB??/\fR at
288the end of a line) can, by changing where the comment begins or ends.
289Therefore, only trigraphs that would form escaped newlines produce
290warnings inside a comment.
291.Sp
292This option is implied by \fB\-Wall\fR. If \fB\-Wall\fR is not
293given, this option is still enabled unless trigraphs are enabled. To
294get trigraph conversion without warnings, but get the other
295\&\fB\-Wall\fR warnings, use \fB\-trigraphs \-Wall \-Wno\-trigraphs\fR.
296.IP "\fB\-Wtraditional\fR" 4
297.IX Item "-Wtraditional"
298Warn about certain constructs that behave differently in traditional and
299\&\s-1ISO\s0 C. Also warn about \s-1ISO\s0 C constructs that have no traditional C
300equivalent, and problematic constructs which should be avoided.
301.IP "\fB\-Wimport\fR" 4
302.IX Item "-Wimport"
303Warn the first time \fB#import\fR is used.
304.IP "\fB\-Wundef\fR" 4
305.IX Item "-Wundef"
306Warn whenever an identifier which is not a macro is encountered in an
307\&\fB#if\fR directive, outside of \fBdefined\fR. Such identifiers are
308replaced with zero.
309.IP "\fB\-Wunused\-macros\fR" 4
310.IX Item "-Wunused-macros"
311Warn about macros defined in the main file that are unused. A macro
312is \fIused\fR if it is expanded or tested for existence at least once.
313The preprocessor will also warn if the macro has not been used at the
314time it is redefined or undefined.
315.Sp
316Built-in macros, macros defined on the command line, and macros
317defined in include files are not warned about.
318.Sp
319\&\fBNote:\fR If a macro is actually used, but only used in skipped
320conditional blocks, then \s-1CPP\s0 will report it as unused. To avoid the
321warning in such a case, you might improve the scope of the macro's
322definition by, for example, moving it into the first skipped block.
323Alternatively, you could provide a dummy use with something like:
324.Sp
325.Vb 2
326\& #if defined the_macro_causing_the_warning
327\& #endif
328.Ve
329.IP "\fB\-Wendif\-labels\fR" 4
330.IX Item "-Wendif-labels"
331Warn whenever an \fB#else\fR or an \fB#endif\fR are followed by text.
332This usually happens in code of the form
333.Sp
334.Vb 5
335\& #if FOO
336\& ...
337\& #else FOO
338\& ...
339\& #endif FOO
340.Ve
341.Sp
342The second and third \f(CW\*(C`FOO\*(C'\fR should be in comments, but often are not
343in older programs. This warning is on by default.
344.IP "\fB\-Werror\fR" 4
345.IX Item "-Werror"
346Make all warnings into hard errors. Source code which triggers warnings
347will be rejected.
348.IP "\fB\-Wsystem\-headers\fR" 4
349.IX Item "-Wsystem-headers"
350Issue warnings for code in system headers. These are normally unhelpful
351in finding bugs in your own code, therefore suppressed. If you are
352responsible for the system library, you may want to see them.
353.IP "\fB\-w\fR" 4
354.IX Item "-w"
355Suppress all warnings, including those which \s-1GNU\s0 \s-1CPP\s0 issues by default.
356.IP "\fB\-pedantic\fR" 4
357.IX Item "-pedantic"
358Issue all the mandatory diagnostics listed in the C standard. Some of
359them are left out by default, since they trigger frequently on harmless
360code.
361.IP "\fB\-pedantic\-errors\fR" 4
362.IX Item "-pedantic-errors"
363Issue all the mandatory diagnostics, and make all mandatory diagnostics
364into errors. This includes mandatory diagnostics that \s-1GCC\s0 issues
365without \fB\-pedantic\fR but treats as warnings.
366.IP "\fB\-M\fR" 4
367.IX Item "-M"
368Instead of outputting the result of preprocessing, output a rule
369suitable for \fBmake\fR describing the dependencies of the main
370source file. The preprocessor outputs one \fBmake\fR rule containing
371the object file name for that source file, a colon, and the names of all
372the included files, including those coming from \fB\-include\fR or
373\&\fB\-imacros\fR command line options.
374.Sp
--- 5 unchanged lines hidden (view full) ---
380.Sp
381This option does not suppress the preprocessor's debug output, such as
382\&\fB\-dM\fR. To avoid mixing such debug output with the dependency
383rules you should explicitly specify the dependency output file with
384\&\fB\-MF\fR, or use an environment variable like
385\&\fB\s-1DEPENDENCIES_OUTPUT\s0\fR. Debug output
386will still be sent to the regular output stream as normal.
387.Sp
388Passing \fB\-M\fR to the driver implies \fB\-E\fR, and suppresses
389warnings with an implicit \fB\-w\fR.
390.IP "\fB\-MM\fR" 4
391.IX Item "-MM"
392Like \fB\-M\fR but do not mention header files that are found in
393system header directories, nor header files that are included,
394directly or indirectly, from such a header.
395.Sp
396This implies that the choice of angle brackets or double quotes in an
397\&\fB#include\fR directive does not in itself determine whether that
398header will appear in \fB\-MM\fR dependency output. This is a
399slight change in semantics from \s-1GCC\s0 versions 3.0 and earlier.
400.Sp
401@anchor{dashMF}
402.IP "\fB\-MF\fR \fIfile\fR" 4
403.IX Item "-MF file"
404When used with \fB\-M\fR or \fB\-MM\fR, specifies a
405file to write the dependencies to. If no \fB\-MF\fR switch is given
406the preprocessor sends the rules to the same place it would have sent
407preprocessed output.
408.Sp
409When used with the driver options \fB\-MD\fR or \fB\-MMD\fR,
410\&\fB\-MF\fR overrides the default dependency output file.
411.IP "\fB\-MG\fR" 4
412.IX Item "-MG"
413In conjunction with an option such as \fB\-M\fR requesting
414dependency generation, \fB\-MG\fR assumes missing header files are
415generated files and adds them to the dependency list without raising
416an error. The dependency filename is taken directly from the
417\&\f(CW\*(C`#include\*(C'\fR directive without prepending any path. \fB\-MG\fR
418also suppresses preprocessed output, as a missing header file renders
419this useless.
420.Sp
421This feature is used in automatic updating of makefiles.
422.IP "\fB\-MP\fR" 4
423.IX Item "-MP"
424This option instructs \s-1CPP\s0 to add a phony target for each dependency
425other than the main file, causing each to depend on nothing. These
426dummy rules work around errors \fBmake\fR gives if you remove header
427files without updating the \fIMakefile\fR to match.
428.Sp
429This is typical output:
430.Sp
431.Vb 1
432\& test.o: test.c test.h
433.Ve
434.Sp
435.Vb 1
436\& test.h:
437.Ve
438.IP "\fB\-MT\fR \fItarget\fR" 4
439.IX Item "-MT target"
440Change the target of the rule emitted by dependency generation. By
441default \s-1CPP\s0 takes the name of the main input file, including any path,
442deletes any file suffix such as \fB.c\fR, and appends the platform's
443usual object suffix. The result is the target.
444.Sp
445An \fB\-MT\fR option will set the target to be exactly the string you
446specify. If you want multiple targets, you can specify them as a single
447argument to \fB\-MT\fR, or use multiple \fB\-MT\fR options.
448.Sp
449For example, \fB\-MT\ '$(objpfx)foo.o'\fR might give
450.Sp
451.Vb 1
452\& $(objpfx)foo.o: foo.c
453.Ve
454.IP "\fB\-MQ\fR \fItarget\fR" 4
455.IX Item "-MQ target"
456Same as \fB\-MT\fR, but it quotes any characters which are special to
457Make. \fB\-MQ\ '$(objpfx)foo.o'\fR gives
458.Sp
459.Vb 1
460\& $$(objpfx)foo.o: foo.c
461.Ve
462.Sp
463The default target is automatically quoted, as if it were given with
464\&\fB\-MQ\fR.
465.IP "\fB\-MD\fR" 4
466.IX Item "-MD"
467\&\fB\-MD\fR is equivalent to \fB\-M \-MF\fR \fIfile\fR, except that
468\&\fB\-E\fR is not implied. The driver determines \fIfile\fR based on
469whether an \fB\-o\fR option is given. If it is, the driver uses its
470argument but with a suffix of \fI.d\fR, otherwise it take the
471basename of the input file and applies a \fI.d\fR suffix.
472.Sp
473If \fB\-MD\fR is used in conjunction with \fB\-E\fR, any
474\&\fB\-o\fR switch is understood to specify the dependency output file
475(but \f(CW@pxref\fR{dashMF,,\-MF}), but if used without \fB\-E\fR, each \fB\-o\fR
476is understood to specify a target object file.
477.Sp
478Since \fB\-E\fR is not implied, \fB\-MD\fR can be used to generate
479a dependency output file as a side-effect of the compilation process.
480.IP "\fB\-MMD\fR" 4
481.IX Item "-MMD"
482Like \fB\-MD\fR except mention only user header files, not system
483\&\-header files.
484.IP "\fB\-x c\fR" 4
485.IX Item "-x c"
486.PD 0
487.IP "\fB\-x c++\fR" 4
488.IX Item "-x c++"
489.IP "\fB\-x objective-c\fR" 4
490.IX Item "-x objective-c"
491.IP "\fB\-x assembler-with-cpp\fR" 4
492.IX Item "-x assembler-with-cpp"
493.PD
494Specify the source language: C, \*(C+, Objective\-C, or assembly. This has
495nothing to do with standards conformance or extensions; it merely
496selects which base syntax to expect. If you give none of these options,
497cpp will deduce the language from the extension of the source file:
498\&\fB.c\fR, \fB.cc\fR, \fB.m\fR, or \fB.S\fR. Some other common
499extensions for \*(C+ and assembly are also recognized. If cpp does not
500recognize the extension, it will treat the file as C; this is the most
501generic mode.
502.Sp
503\&\fBNote:\fR Previous versions of cpp accepted a \fB\-lang\fR option
504which selected both the language and the standards conformance level.
505This option has been removed, because it conflicts with the \fB\-l\fR
506option.
507.IP "\fB\-std=\fR\fIstandard\fR" 4
508.IX Item "-std=standard"
509.PD 0
510.IP "\fB\-ansi\fR" 4
511.IX Item "-ansi"
512.PD
513Specify the standard to which the code should conform. Currently \s-1CPP\s0
514knows about C and \*(C+ standards; others may be added in the future.
515.Sp
516\&\fIstandard\fR
517may be one of:
518.RS 4
519.ie n .IP """iso9899:1990""" 4
520.el .IP "\f(CWiso9899:1990\fR" 4
521.IX Item "iso9899:1990"
522.PD 0
523.ie n .IP """c89""" 4
524.el .IP "\f(CWc89\fR" 4
525.IX Item "c89"
526.PD
527The \s-1ISO\s0 C standard from 1990. \fBc89\fR is the customary shorthand for
528this version of the standard.
529.Sp
530The \fB\-ansi\fR option is equivalent to \fB\-std=c89\fR.
531.ie n .IP """iso9899:199409""" 4
532.el .IP "\f(CWiso9899:199409\fR" 4
533.IX Item "iso9899:199409"
534The 1990 C standard, as amended in 1994.
535.ie n .IP """iso9899:1999""" 4
536.el .IP "\f(CWiso9899:1999\fR" 4
537.IX Item "iso9899:1999"
538.PD 0
539.ie n .IP """c99""" 4
540.el .IP "\f(CWc99\fR" 4
541.IX Item "c99"
542.ie n .IP """iso9899:199x""" 4
543.el .IP "\f(CWiso9899:199x\fR" 4
544.IX Item "iso9899:199x"
545.ie n .IP """c9x""" 4
546.el .IP "\f(CWc9x\fR" 4
547.IX Item "c9x"
548.PD
549The revised \s-1ISO\s0 C standard, published in December 1999. Before
550publication, this was known as C9X.
551.ie n .IP """gnu89""" 4
552.el .IP "\f(CWgnu89\fR" 4
553.IX Item "gnu89"
554The 1990 C standard plus \s-1GNU\s0 extensions. This is the default.
555.ie n .IP """gnu99""" 4
556.el .IP "\f(CWgnu99\fR" 4
557.IX Item "gnu99"
558.PD 0
559.ie n .IP """gnu9x""" 4
560.el .IP "\f(CWgnu9x\fR" 4
561.IX Item "gnu9x"
562.PD
563The 1999 C standard plus \s-1GNU\s0 extensions.
564.ie n .IP """c++98""" 4
565.el .IP "\f(CWc++98\fR" 4
566.IX Item "c++98"
567The 1998 \s-1ISO\s0 \*(C+ standard plus amendments.
568.ie n .IP """gnu++98""" 4
569.el .IP "\f(CWgnu++98\fR" 4
570.IX Item "gnu++98"
571The same as \fB\-std=c++98\fR plus \s-1GNU\s0 extensions. This is the
572default for \*(C+ code.
573.RE
574.RS 4
575.RE
576.IP "\fB\-I\-\fR" 4
577.IX Item "-I-"
578Split the include path. Any directories specified with \fB\-I\fR
579options before \fB\-I\-\fR are searched only for headers requested with
580\&\f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR; they are not searched for
581\&\f(CW\*(C`#include\ <\f(CIfile\f(CW>\*(C'\fR. If additional directories are
582specified with \fB\-I\fR options after the \fB\-I\-\fR, those
583directories are searched for all \fB#include\fR directives.
584.Sp
585In addition, \fB\-I\-\fR inhibits the use of the directory of the current
586file directory as the first search directory for \f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR.
587.IP "\fB\-nostdinc\fR" 4
588.IX Item "-nostdinc"
589Do not search the standard system directories for header files.
590Only the directories you have specified with \fB\-I\fR options
591(and the directory of the current file, if appropriate) are searched.
592.IP "\fB\-nostdinc++\fR" 4
593.IX Item "-nostdinc++"
594Do not search for header files in the \*(C+\-specific standard directories,
595but do still search the other standard directories. (This option is
596used when building the \*(C+ library.)
597.IP "\fB\-include\fR \fIfile\fR" 4
598.IX Item "-include file"
599Process \fIfile\fR as if \f(CW\*(C`#include "file"\*(C'\fR appeared as the first
600line of the primary source file. However, the first directory searched
601for \fIfile\fR is the preprocessor's working directory \fIinstead of\fR
602the directory containing the main source file. If not found there, it
603is searched for in the remainder of the \f(CW\*(C`#include "..."\*(C'\fR search
604chain as normal.
605.Sp
606If multiple \fB\-include\fR options are given, the files are included
607in the order they appear on the command line.
608.IP "\fB\-imacros\fR \fIfile\fR" 4
609.IX Item "-imacros file"
610Exactly like \fB\-include\fR, except that any output produced by
611scanning \fIfile\fR is thrown away. Macros it defines remain defined.
612This allows you to acquire all the macros from a header without also
613processing its declarations.
614.Sp
615All files specified by \fB\-imacros\fR are processed before all files
616specified by \fB\-include\fR.
617.IP "\fB\-idirafter\fR \fIdir\fR" 4
618.IX Item "-idirafter dir"
619Search \fIdir\fR for header files, but do it \fIafter\fR all
620directories specified with \fB\-I\fR and the standard system directories
621have been exhausted. \fIdir\fR is treated as a system include directory.
622.IP "\fB\-iprefix\fR \fIprefix\fR" 4
623.IX Item "-iprefix prefix"
624Specify \fIprefix\fR as the prefix for subsequent \fB\-iwithprefix\fR
625options. If the prefix represents a directory, you should include the
626final \fB/\fR.
627.IP "\fB\-iwithprefix\fR \fIdir\fR" 4
628.IX Item "-iwithprefix dir"
629.PD 0
630.IP "\fB\-iwithprefixbefore\fR \fIdir\fR" 4
631.IX Item "-iwithprefixbefore dir"
632.PD
633Append \fIdir\fR to the prefix specified previously with
634\&\fB\-iprefix\fR, and add the resulting directory to the include search
635path. \fB\-iwithprefixbefore\fR puts it in the same place \fB\-I\fR
636would; \fB\-iwithprefix\fR puts it where \fB\-idirafter\fR would.
637.IP "\fB\-isystem\fR \fIdir\fR" 4
638.IX Item "-isystem dir"
639Search \fIdir\fR for header files, after all directories specified by
640\&\fB\-I\fR but before the standard system directories. Mark it
641as a system directory, so that it gets the same special treatment as
642is applied to the standard system directories.
643.IP "\fB\-fdollars\-in\-identifiers\fR" 4
644.IX Item "-fdollars-in-identifiers"
645@anchor{fdollars\-in\-identifiers}
646Accept \fB$\fR in identifiers.
647.IP "\fB\-fpreprocessed\fR" 4
648.IX Item "-fpreprocessed"
649Indicate to the preprocessor that the input file has already been
650preprocessed. This suppresses things like macro expansion, trigraph
651conversion, escaped newline splicing, and processing of most directives.
652The preprocessor still recognizes and removes comments, so that you can
653pass a file preprocessed with \fB\-C\fR to the compiler without
654problems. In this mode the integrated preprocessor is little more than
655a tokenizer for the front ends.
656.Sp
657\&\fB\-fpreprocessed\fR is implicit if the input file has one of the
658extensions \fB.i\fR, \fB.ii\fR or \fB.mi\fR. These are the
659extensions that \s-1GCC\s0 uses for preprocessed files created by
660\&\fB\-save\-temps\fR.
661.IP "\fB\-ftabstop=\fR\fIwidth\fR" 4
662.IX Item "-ftabstop=width"
663Set the distance between tab stops. This helps the preprocessor report
664correct column numbers in warnings or errors, even if tabs appear on the
665line. If the value is less than 1 or greater than 100, the option is
666ignored. The default is 8.
667.IP "\fB\-fexec\-charset=\fR\fIcharset\fR" 4
668.IX Item "-fexec-charset=charset"
669Set the execution character set, used for string and character
670constants. The default is \s-1UTF\-8\s0. \fIcharset\fR can be any encoding
671supported by the system's \f(CW\*(C`iconv\*(C'\fR library routine.
672.IP "\fB\-fwide\-exec\-charset=\fR\fIcharset\fR" 4
673.IX Item "-fwide-exec-charset=charset"
674Set the wide execution character set, used for wide string and
675character constants. The default is \s-1UTF\-32\s0 or \s-1UTF\-16\s0, whichever
676corresponds to the width of \f(CW\*(C`wchar_t\*(C'\fR. As with
677\&\fB\-ftarget\-charset\fR, \fIcharset\fR can be any encoding supported
678by the system's \f(CW\*(C`iconv\*(C'\fR library routine; however, you will have
679problems with encodings that do not fit exactly in \f(CW\*(C`wchar_t\*(C'\fR.
680.IP "\fB\-finput\-charset=\fR\fIcharset\fR" 4
681.IX Item "-finput-charset=charset"
682Set the input character set, used for translation from the character
683set of the input file to the source character set used by \s-1GCC\s0. If the
684locale does not specify, or \s-1GCC\s0 cannot get this information from the
685locale, the default is \s-1UTF\-8\s0. This can be overridden by either the locale
686or this command line option. Currently the command line option takes
687precedence if there's a conflict. \fIcharset\fR can be any encoding
688supported by the system's \f(CW\*(C`iconv\*(C'\fR library routine.
689.IP "\fB\-fworking\-directory\fR" 4
690.IX Item "-fworking-directory"
691Enable generation of linemarkers in the preprocessor output that will
692let the compiler know the current working directory at the time of
693preprocessing. When this option is enabled, the preprocessor will
694emit, after the initial linemarker, a second linemarker with the
695current working directory followed by two slashes. \s-1GCC\s0 will use this
696directory, when it's present in the preprocessed input, as the
697directory emitted as the current working directory in some debugging
698information formats. This option is implicitly enabled if debugging
699information is enabled, but this can be inhibited with the negated
700form \fB\-fno\-working\-directory\fR. If the \fB\-P\fR flag is
701present in the command line, this option has no effect, since no
702\&\f(CW\*(C`#line\*(C'\fR directives are emitted whatsoever.
703.IP "\fB\-fno\-show\-column\fR" 4
704.IX Item "-fno-show-column"
705Do not print column numbers in diagnostics. This may be necessary if
706diagnostics are being scanned by a program that does not understand the
707column numbers, such as \fBdejagnu\fR.
708.IP "\fB\-A\fR \fIpredicate\fR\fB=\fR\fIanswer\fR" 4
709.IX Item "-A predicate=answer"
710Make an assertion with the predicate \fIpredicate\fR and answer
711\&\fIanswer\fR. This form is preferred to the older form \fB\-A\fR
712\&\fIpredicate\fR\fB(\fR\fIanswer\fR\fB)\fR, which is still supported, because
713it does not use shell special characters.
714.IP "\fB\-A \-\fR\fIpredicate\fR\fB=\fR\fIanswer\fR" 4
715.IX Item "-A -predicate=answer"
716Cancel an assertion with the predicate \fIpredicate\fR and answer
717\&\fIanswer\fR.
718.IP "\fB\-dCHARS\fR" 4
719.IX Item "-dCHARS"
720\&\fI\s-1CHARS\s0\fR is a sequence of one or more of the following characters,
721and must not be preceded by a space. Other characters are interpreted
722by the compiler proper, or reserved for future versions of \s-1GCC\s0, and so
723are silently ignored. If you specify characters whose behavior
724conflicts, the result is undefined.
725.RS 4
726.IP "\fBM\fR" 4
727.IX Item "M"
728Instead of the normal output, generate a list of \fB#define\fR
729directives for all the macros defined during the execution of the
730preprocessor, including predefined macros. This gives you a way of
731finding out what is predefined in your version of the preprocessor.
732Assuming you have no file \fIfoo.h\fR, the command
733.Sp
734.Vb 1
735\& touch foo.h; cpp -dM foo.h
736.Ve
737.Sp
738will show all the predefined macros.
739.IP "\fBD\fR" 4
740.IX Item "D"
741Like \fBM\fR except in two respects: it does \fInot\fR include the
742predefined macros, and it outputs \fIboth\fR the \fB#define\fR
743directives and the result of preprocessing. Both kinds of output go to
744the standard output file.
745.IP "\fBN\fR" 4
746.IX Item "N"
747Like \fBD\fR, but emit only the macro names, not their expansions.
748.IP "\fBI\fR" 4
749.IX Item "I"
750Output \fB#include\fR directives in addition to the result of
751preprocessing.
752.RE
753.RS 4
754.RE
755.IP "\fB\-P\fR" 4
756.IX Item "-P"
757Inhibit generation of linemarkers in the output from the preprocessor.
758This might be useful when running the preprocessor on something that is
759not C code, and will be sent to a program which might be confused by the
760linemarkers.
761.IP "\fB\-C\fR" 4
762.IX Item "-C"
763Do not discard comments. All comments are passed through to the output
764file, except for comments in processed directives, which are deleted
765along with the directive.
766.Sp
767You should be prepared for side effects when using \fB\-C\fR; it
768causes the preprocessor to treat comments as tokens in their own right.
769For example, comments appearing at the start of what would be a
770directive line have the effect of turning that line into an ordinary
771source line, since the first token on the line is no longer a \fB#\fR.
772.IP "\fB\-CC\fR" 4
773.IX Item "-CC"
774Do not discard comments, including during macro expansion. This is
775like \fB\-C\fR, except that comments contained within macros are
776also passed through to the output file where the macro is expanded.
777.Sp
778In addition to the side-effects of the \fB\-C\fR option, the
779\&\fB\-CC\fR option causes all \*(C+\-style comments inside a macro
780to be converted to C\-style comments. This is to prevent later use
781of that macro from inadvertently commenting out the remainder of
782the source line.
783.Sp
784The \fB\-CC\fR option is generally used to support lint comments.
785.IP "\fB\-traditional\-cpp\fR" 4
786.IX Item "-traditional-cpp"
787Try to imitate the behavior of old-fashioned C preprocessors, as
788opposed to \s-1ISO\s0 C preprocessors.
789.IP "\fB\-trigraphs\fR" 4
790.IX Item "-trigraphs"
791Process trigraph sequences.
792.IP "\fB\-remap\fR" 4
793.IX Item "-remap"
794Enable special code to work around file systems which only permit very
795short file names, such as \s-1MS\-DOS\s0.
796.IP "\fB\-\-help\fR" 4
797.IX Item "--help"
798.PD 0
799.IP "\fB\-\-target\-help\fR" 4
800.IX Item "--target-help"
801.PD
802Print text describing all the command line options instead of
803preprocessing anything.
804.IP "\fB\-v\fR" 4
805.IX Item "-v"
806Verbose mode. Print out \s-1GNU\s0 \s-1CPP\s0's version number at the beginning of
807execution, and report the final form of the include path.
808.IP "\fB\-H\fR" 4
809.IX Item "-H"
810Print the name of each header file used, in addition to other normal
811activities. Each name is indented to show how deep in the
812\&\fB#include\fR stack it is. Precompiled header files are also
813printed, even if they are found to be invalid; an invalid precompiled
814header file is printed with \fB...x\fR and a valid one with \fB...!\fR .
815.IP "\fB\-version\fR" 4
816.IX Item "-version"
817.PD 0
818.IP "\fB\-\-version\fR" 4
819.IX Item "--version"
820.PD
821Print out \s-1GNU\s0 \s-1CPP\s0's version number. With one dash, proceed to
822preprocess as normal. With two dashes, exit immediately.
823.SH "ENVIRONMENT"
824.IX Header "ENVIRONMENT"
825This section describes the environment variables that affect how \s-1CPP\s0
826operates. You can use them to specify directories or prefixes to use
827when searching for include files, or to control dependency output.
828.PP
829Note that you can also specify places to search using options such as
830\&\fB\-I\fR, and control dependency output with options like
831\&\fB\-M\fR. These take precedence over
832environment variables, which in turn take precedence over the
833configuration of \s-1GCC\s0.
834.IP "\fB\s-1CPATH\s0\fR" 4
835.IX Item "CPATH"
836.PD 0
837.IP "\fBC_INCLUDE_PATH\fR" 4
838.IX Item "C_INCLUDE_PATH"
839.IP "\fB\s-1CPLUS_INCLUDE_PATH\s0\fR" 4
840.IX Item "CPLUS_INCLUDE_PATH"
841.IP "\fB\s-1OBJC_INCLUDE_PATH\s0\fR" 4
842.IX Item "OBJC_INCLUDE_PATH"
843.PD
844Each variable's value is a list of directories separated by a special
845character, much like \fB\s-1PATH\s0\fR, in which to look for header files.
846The special character, \f(CW\*(C`PATH_SEPARATOR\*(C'\fR, is target-dependent and
847determined at \s-1GCC\s0 build time. For Microsoft Windows-based targets it is a
848semicolon, and for almost all other targets it is a colon.
849.Sp
850\&\fB\s-1CPATH\s0\fR specifies a list of directories to be searched as if
851specified with \fB\-I\fR, but after any paths given with \fB\-I\fR
852options on the command line. This environment variable is used
853regardless of which language is being preprocessed.
854.Sp
855The remaining environment variables apply only when preprocessing the
856particular language indicated. Each specifies a list of directories
857to be searched as if specified with \fB\-isystem\fR, but after any
858paths given with \fB\-isystem\fR options on the command line.
859.Sp
860In all these variables, an empty element instructs the compiler to
861search its current working directory. Empty elements can appear at the
862beginning or end of a path. For instance, if the value of
863\&\fB\s-1CPATH\s0\fR is \f(CW\*(C`:/special/include\*(C'\fR, that has the same
864effect as \fB\-I.\ \-I/special/include\fR.
865.IP "\fB\s-1DEPENDENCIES_OUTPUT\s0\fR" 4
866.IX Item "DEPENDENCIES_OUTPUT"
867If this variable is set, its value specifies how to output
868dependencies for Make based on the non-system header files processed
869by the compiler. System header files are ignored in the dependency
870output.
871.Sp
872The value of \fB\s-1DEPENDENCIES_OUTPUT\s0\fR can be just a file name, in
873which case the Make rules are written to that file, guessing the target
874name from the source file name. Or the value can have the form
875\&\fIfile\fR\fB \fR\fItarget\fR, in which case the rules are written to
876file \fIfile\fR using \fItarget\fR as the target name.
877.Sp
878In other words, this environment variable is equivalent to combining
879the options \fB\-MM\fR and \fB\-MF\fR,
880with an optional \fB\-MT\fR switch too.
881.IP "\fB\s-1SUNPRO_DEPENDENCIES\s0\fR" 4
882.IX Item "SUNPRO_DEPENDENCIES"
883This variable is the same as \fB\s-1DEPENDENCIES_OUTPUT\s0\fR (see above),
884except that system header files are not ignored, so it implies
885\&\fB\-M\fR rather than \fB\-MM\fR. However, the dependence on the
886main input file is omitted.
887.SH "SEE ALSO"
888.IX Header "SEE ALSO"
889\&\fIgpl\fR\|(7), \fIgfdl\fR\|(7), \fIfsf\-funding\fR\|(7),
890\&\fIgcc\fR\|(1), \fIas\fR\|(1), \fIld\fR\|(1), and the Info entries for \fIcpp\fR, \fIgcc\fR, and
891\&\fIbinutils\fR.
892.SH "COPYRIGHT"
893.IX Header "COPYRIGHT"
894Copyright (c) 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996,
8951997, 1998, 1999, 2000, 2001, 2002, 2003, 2004
896Free Software Foundation, Inc.
897.PP
898Permission is granted to copy, distribute and/or modify this document
899under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.1 or
900any later version published by the Free Software Foundation. A copy of
901the license is included in the
902man page \fIgfdl\fR\|(7).
903This manual contains no Invariant Sections. The Front-Cover Texts are
904(a) (see below), and the Back-Cover Texts are (b) (see below).
905.PP
906(a) The \s-1FSF\s0's Front-Cover Text is:
907.PP
908.Vb 1
909\& A GNU Manual
910.Ve
911.PP
912(b) The \s-1FSF\s0's Back-Cover Text is:
913.PP
914.Vb 3
915\& You have freedom to copy and modify this GNU Manual, like GNU
916\& software. Copies published by the Free Software Foundation raise
917\& funds for GNU development.
918.Ve
2.\"
3.\" Standard preamble:
4.\" ========================================================================
5.de Sh \" Subsection heading
6.br
7.if t .Sp
8.ne 5
9.PP
10\fB\\$1\fR
11.PP
12..
13.de Sp \" Vertical space (when we can't use .PP)
14.if t .sp .5v
15.if n .sp
16..
17.de Vb \" Begin verbatim text
18.ft CW
19.nf
20.ne \\$1
21..
22.de Ve \" End verbatim text
23.ft R
24.fi
25..
26.\" Set up some character translations and predefined strings. \*(-- will
27.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
28.\" double quote, and \*(R" will give a right double quote. | will give a
29.\" real vertical bar. \*(C+ will give a nicer C++. Capital omega is used to
30.\" do unbreakable dashes and therefore won't be available. \*(C` and \*(C'
31.\" expand to `' in nroff, nothing in troff, for use with C<>.
32.tr \(*W-|\(bv\*(Tr
33.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
34.ie n \{\
35. ds -- \(*W-
36. ds PI pi
37. if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
38. if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch
39. ds L" ""
40. ds R" ""
41. ds C` ""
42. ds C' ""
43'br\}
44.el\{\
45. ds -- \|\(em\|
46. ds PI \(*p
47. ds L" ``
48. ds R" ''
49'br\}
50.\"
51.\" If the F register is turned on, we'll generate index entries on stderr for
52.\" titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and index
53.\" entries marked with X<> in POD. Of course, you'll have to process the
54.\" output yourself in some meaningful fashion.
55.if \nF \{\
56. de IX
57. tm Index:\\$1\t\\n%\t"\\$2"
58..
59. nr % 0
60. rr F
61.\}
62.\"
63.\" For nroff, turn off justification. Always turn off hyphenation; it makes
64.\" way too many mistakes in technical documents.
65.hy 0
66.if n .na
67.\"
68.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
69.\" Fear. Run. Save yourself. No user-serviceable parts.
70. \" fudge factors for nroff and troff
71.if n \{\
72. ds #H 0
73. ds #V .8m
74. ds #F .3m
75. ds #[ \f1
76. ds #] \fP
77.\}
--- 43 unchanged lines hidden (view full) ---
121. ds d- d\h'-1'\(ga
122. ds D- D\h'-1'\(hy
123. ds th \o'bp'
124. ds Th \o'LP'
125. ds ae ae
126. ds Ae AE
127.\}
128.rm #[ #] #H #V #F C
129.\" ========================================================================
130.\"
131.IX Title "CPP 1"
132.TH CPP 1 "2006-03-06" "gcc-3.4.6" "GNU"
133.SH "NAME"
134cpp \- The C Preprocessor
135.SH "SYNOPSIS"
136.IX Header "SYNOPSIS"
137cpp [\fB\-D\fR\fImacro\fR[=\fIdefn\fR]...] [\fB\-U\fR\fImacro\fR]
138 [\fB\-I\fR\fIdir\fR...] [\fB\-W\fR\fIwarn\fR...]
139 [\fB\-M\fR|\fB\-MM\fR] [\fB\-MG\fR] [\fB\-MF\fR \fIfilename\fR]
140 [\fB\-MP\fR] [\fB\-MQ\fR \fItarget\fR...]
141 [\fB\-MT\fR \fItarget\fR...]
142 [\fB\-P\fR] [\fB\-fno\-working\-directory\fR]
143 [\fB\-x\fR \fIlanguage\fR] [\fB\-std=\fR\fIstandard\fR]
144 \fIinfile\fR \fIoutfile\fR
145.PP
146Only the most useful options are listed here; see below for the remainder.
147.SH "DESCRIPTION"
148.IX Header "DESCRIPTION"
149The C preprocessor, often known as \fIcpp\fR, is a \fImacro processor\fR
150that is used automatically by the C compiler to transform your program
151before compilation. It is called a macro processor because it allows
152you to define \fImacros\fR, which are brief abbreviations for longer
153constructs.
154.PP
155The C preprocessor is intended to be used only with C, \*(C+, and
156Objective-C source code. In the past, it has been abused as a general
157text processor. It will choke on input which does not obey C's lexical
158rules. For example, apostrophes will be interpreted as the beginning of
159character constants, and cause errors. Also, you cannot rely on it
160preserving characteristics of the input which are not significant to
161C\-family languages. If a Makefile is preprocessed, all the hard tabs
162will be removed, and the Makefile will not work.
163.PP
164Having said that, you can often get away with using cpp on things which
165are not C. Other Algol-ish programming languages are often safe
166(Pascal, Ada, etc.) So is assembly, with caution. \fB\-traditional\-cpp\fR
167mode preserves more white space, and is otherwise more permissive. Many
168of the problems can be avoided by writing C or \*(C+ style comments
169instead of native language comments, and keeping macros simple.
170.PP
171Wherever possible, you should use a preprocessor geared to the language
172you are writing in. Modern versions of the \s-1GNU\s0 assembler have macro
173facilities. Most high level programming languages have their own
174conditional compilation and inclusion mechanism. If all else fails,
175try a true general text processor, such as \s-1GNU\s0 M4.
176.PP
177C preprocessors vary in some details. This manual discusses the \s-1GNU\s0 C
178preprocessor, which provides a small superset of the features of \s-1ISO\s0
179Standard C. In its default mode, the \s-1GNU\s0 C preprocessor does not do a
180few things required by the standard. These are features which are
181rarely, if ever, used, and may cause surprising changes to the meaning
182of a program which does not expect them. To get strict \s-1ISO\s0 Standard C,
183you should use the \fB\-std=c89\fR or \fB\-std=c99\fR options, depending
184on which version of the standard you want. To get all the mandatory
185diagnostics, you must also use \fB\-pedantic\fR.
186.PP
187This manual describes the behavior of the \s-1ISO\s0 preprocessor. To
188minimize gratuitous differences, where the \s-1ISO\s0 preprocessor's
189behavior does not conflict with traditional semantics, the
190traditional preprocessor should behave the same way. The various
191differences that do exist are detailed in the section \fBTraditional
192Mode\fR.
193.PP
194For clarity, unless noted otherwise, references to \fB\s-1CPP\s0\fR in this
195manual refer to \s-1GNU\s0 \s-1CPP\s0.
196.SH "OPTIONS"
197.IX Header "OPTIONS"
198The C preprocessor expects two file names as arguments, \fIinfile\fR and
199\&\fIoutfile\fR. The preprocessor reads \fIinfile\fR together with any
200other files it specifies with \fB#include\fR. All the output generated
201by the combined input files is written in \fIoutfile\fR.
202.PP
203Either \fIinfile\fR or \fIoutfile\fR may be \fB\-\fR, which as
204\&\fIinfile\fR means to read from standard input and as \fIoutfile\fR
205means to write to standard output. Also, if either file is omitted, it
206means the same as if \fB\-\fR had been specified for that file.
207.PP
208Unless otherwise noted, or the option ends in \fB=\fR, all options
209which take an argument may have that argument appear either immediately
210after the option, or with a space between option and argument:
211\&\fB\-Ifoo\fR and \fB\-I foo\fR have the same effect.
212.PP
213Many options have multi-letter names; therefore multiple single-letter
214options may \fInot\fR be grouped: \fB\-dM\fR is very different from
215\&\fB\-d\ \-M\fR.
216.IP "\fB\-D\fR \fIname\fR" 4
217.IX Item "-D name"
218Predefine \fIname\fR as a macro, with definition \f(CW1\fR.
219.IP "\fB\-D\fR \fIname\fR\fB=\fR\fIdefinition\fR" 4
220.IX Item "-D name=definition"
221Predefine \fIname\fR as a macro, with definition \fIdefinition\fR.
222The contents of \fIdefinition\fR are tokenized and processed as if
223they appeared during translation phase three in a \fB#define\fR
224directive. In particular, the definition will be truncated by
225embedded newline characters.
226.Sp
227If you are invoking the preprocessor from a shell or shell-like
228program you may need to use the shell's quoting syntax to protect
229characters such as spaces that have a meaning in the shell syntax.
230.Sp
231If you wish to define a function-like macro on the command line, write
232its argument list with surrounding parentheses before the equals sign
233(if any). Parentheses are meaningful to most shells, so you will need
234to quote the option. With \fBsh\fR and \fBcsh\fR,
235\&\fB\-D'\fR\fIname\fR\fB(\fR\fIargs...\fR\fB)=\fR\fIdefinition\fR\fB'\fR works.
236.Sp
237\&\fB\-D\fR and \fB\-U\fR options are processed in the order they
238are given on the command line. All \fB\-imacros\fR \fIfile\fR and
239\&\fB\-include\fR \fIfile\fR options are processed after all
240\&\fB\-D\fR and \fB\-U\fR options.
241.IP "\fB\-U\fR \fIname\fR" 4
242.IX Item "-U name"
243Cancel any previous definition of \fIname\fR, either built in or
244provided with a \fB\-D\fR option.
245.IP "\fB\-undef\fR" 4
246.IX Item "-undef"
247Do not predefine any system-specific or GCC-specific macros. The
248standard predefined macros remain defined.
249.IP "\fB\-I\fR \fIdir\fR" 4
250.IX Item "-I dir"
251Add the directory \fIdir\fR to the list of directories to be searched
252for header files.
253.Sp
254Directories named by \fB\-I\fR are searched before the standard
255system include directories. If the directory \fIdir\fR is a standard
256system include directory, the option is ignored to ensure that the
257default search order for system directories and the special treatment
258of system headers are not defeated
259\&.
260.IP "\fB\-o\fR \fIfile\fR" 4
261.IX Item "-o file"
262Write output to \fIfile\fR. This is the same as specifying \fIfile\fR
263as the second non-option argument to \fBcpp\fR. \fBgcc\fR has a
264different interpretation of a second non-option argument, so you must
265use \fB\-o\fR to specify the output file.
266.IP "\fB\-Wall\fR" 4
267.IX Item "-Wall"
268Turns on all optional warnings which are desirable for normal code.
269At present this is \fB\-Wcomment\fR, \fB\-Wtrigraphs\fR,
270\&\fB\-Wmultichar\fR and a warning about integer promotion causing a
271change of sign in \f(CW\*(C`#if\*(C'\fR expressions. Note that many of the
272preprocessor's warnings are on by default and have no options to
273control them.
274.IP "\fB\-Wcomment\fR" 4
275.IX Item "-Wcomment"
276.PD 0
277.IP "\fB\-Wcomments\fR" 4
278.IX Item "-Wcomments"
279.PD
280Warn whenever a comment-start sequence \fB/*\fR appears in a \fB/*\fR
281comment, or whenever a backslash-newline appears in a \fB//\fR comment.
282(Both forms have the same effect.)
283.IP "\fB\-Wtrigraphs\fR" 4
284.IX Item "-Wtrigraphs"
285@anchor{Wtrigraphs}
286Most trigraphs in comments cannot affect the meaning of the program.
287However, a trigraph that would form an escaped newline (\fB??/\fR at
288the end of a line) can, by changing where the comment begins or ends.
289Therefore, only trigraphs that would form escaped newlines produce
290warnings inside a comment.
291.Sp
292This option is implied by \fB\-Wall\fR. If \fB\-Wall\fR is not
293given, this option is still enabled unless trigraphs are enabled. To
294get trigraph conversion without warnings, but get the other
295\&\fB\-Wall\fR warnings, use \fB\-trigraphs \-Wall \-Wno\-trigraphs\fR.
296.IP "\fB\-Wtraditional\fR" 4
297.IX Item "-Wtraditional"
298Warn about certain constructs that behave differently in traditional and
299\&\s-1ISO\s0 C. Also warn about \s-1ISO\s0 C constructs that have no traditional C
300equivalent, and problematic constructs which should be avoided.
301.IP "\fB\-Wimport\fR" 4
302.IX Item "-Wimport"
303Warn the first time \fB#import\fR is used.
304.IP "\fB\-Wundef\fR" 4
305.IX Item "-Wundef"
306Warn whenever an identifier which is not a macro is encountered in an
307\&\fB#if\fR directive, outside of \fBdefined\fR. Such identifiers are
308replaced with zero.
309.IP "\fB\-Wunused\-macros\fR" 4
310.IX Item "-Wunused-macros"
311Warn about macros defined in the main file that are unused. A macro
312is \fIused\fR if it is expanded or tested for existence at least once.
313The preprocessor will also warn if the macro has not been used at the
314time it is redefined or undefined.
315.Sp
316Built-in macros, macros defined on the command line, and macros
317defined in include files are not warned about.
318.Sp
319\&\fBNote:\fR If a macro is actually used, but only used in skipped
320conditional blocks, then \s-1CPP\s0 will report it as unused. To avoid the
321warning in such a case, you might improve the scope of the macro's
322definition by, for example, moving it into the first skipped block.
323Alternatively, you could provide a dummy use with something like:
324.Sp
325.Vb 2
326\& #if defined the_macro_causing_the_warning
327\& #endif
328.Ve
329.IP "\fB\-Wendif\-labels\fR" 4
330.IX Item "-Wendif-labels"
331Warn whenever an \fB#else\fR or an \fB#endif\fR are followed by text.
332This usually happens in code of the form
333.Sp
334.Vb 5
335\& #if FOO
336\& ...
337\& #else FOO
338\& ...
339\& #endif FOO
340.Ve
341.Sp
342The second and third \f(CW\*(C`FOO\*(C'\fR should be in comments, but often are not
343in older programs. This warning is on by default.
344.IP "\fB\-Werror\fR" 4
345.IX Item "-Werror"
346Make all warnings into hard errors. Source code which triggers warnings
347will be rejected.
348.IP "\fB\-Wsystem\-headers\fR" 4
349.IX Item "-Wsystem-headers"
350Issue warnings for code in system headers. These are normally unhelpful
351in finding bugs in your own code, therefore suppressed. If you are
352responsible for the system library, you may want to see them.
353.IP "\fB\-w\fR" 4
354.IX Item "-w"
355Suppress all warnings, including those which \s-1GNU\s0 \s-1CPP\s0 issues by default.
356.IP "\fB\-pedantic\fR" 4
357.IX Item "-pedantic"
358Issue all the mandatory diagnostics listed in the C standard. Some of
359them are left out by default, since they trigger frequently on harmless
360code.
361.IP "\fB\-pedantic\-errors\fR" 4
362.IX Item "-pedantic-errors"
363Issue all the mandatory diagnostics, and make all mandatory diagnostics
364into errors. This includes mandatory diagnostics that \s-1GCC\s0 issues
365without \fB\-pedantic\fR but treats as warnings.
366.IP "\fB\-M\fR" 4
367.IX Item "-M"
368Instead of outputting the result of preprocessing, output a rule
369suitable for \fBmake\fR describing the dependencies of the main
370source file. The preprocessor outputs one \fBmake\fR rule containing
371the object file name for that source file, a colon, and the names of all
372the included files, including those coming from \fB\-include\fR or
373\&\fB\-imacros\fR command line options.
374.Sp
--- 5 unchanged lines hidden (view full) ---
380.Sp
381This option does not suppress the preprocessor's debug output, such as
382\&\fB\-dM\fR. To avoid mixing such debug output with the dependency
383rules you should explicitly specify the dependency output file with
384\&\fB\-MF\fR, or use an environment variable like
385\&\fB\s-1DEPENDENCIES_OUTPUT\s0\fR. Debug output
386will still be sent to the regular output stream as normal.
387.Sp
388Passing \fB\-M\fR to the driver implies \fB\-E\fR, and suppresses
389warnings with an implicit \fB\-w\fR.
390.IP "\fB\-MM\fR" 4
391.IX Item "-MM"
392Like \fB\-M\fR but do not mention header files that are found in
393system header directories, nor header files that are included,
394directly or indirectly, from such a header.
395.Sp
396This implies that the choice of angle brackets or double quotes in an
397\&\fB#include\fR directive does not in itself determine whether that
398header will appear in \fB\-MM\fR dependency output. This is a
399slight change in semantics from \s-1GCC\s0 versions 3.0 and earlier.
400.Sp
401@anchor{dashMF}
402.IP "\fB\-MF\fR \fIfile\fR" 4
403.IX Item "-MF file"
404When used with \fB\-M\fR or \fB\-MM\fR, specifies a
405file to write the dependencies to. If no \fB\-MF\fR switch is given
406the preprocessor sends the rules to the same place it would have sent
407preprocessed output.
408.Sp
409When used with the driver options \fB\-MD\fR or \fB\-MMD\fR,
410\&\fB\-MF\fR overrides the default dependency output file.
411.IP "\fB\-MG\fR" 4
412.IX Item "-MG"
413In conjunction with an option such as \fB\-M\fR requesting
414dependency generation, \fB\-MG\fR assumes missing header files are
415generated files and adds them to the dependency list without raising
416an error. The dependency filename is taken directly from the
417\&\f(CW\*(C`#include\*(C'\fR directive without prepending any path. \fB\-MG\fR
418also suppresses preprocessed output, as a missing header file renders
419this useless.
420.Sp
421This feature is used in automatic updating of makefiles.
422.IP "\fB\-MP\fR" 4
423.IX Item "-MP"
424This option instructs \s-1CPP\s0 to add a phony target for each dependency
425other than the main file, causing each to depend on nothing. These
426dummy rules work around errors \fBmake\fR gives if you remove header
427files without updating the \fIMakefile\fR to match.
428.Sp
429This is typical output:
430.Sp
431.Vb 1
432\& test.o: test.c test.h
433.Ve
434.Sp
435.Vb 1
436\& test.h:
437.Ve
438.IP "\fB\-MT\fR \fItarget\fR" 4
439.IX Item "-MT target"
440Change the target of the rule emitted by dependency generation. By
441default \s-1CPP\s0 takes the name of the main input file, including any path,
442deletes any file suffix such as \fB.c\fR, and appends the platform's
443usual object suffix. The result is the target.
444.Sp
445An \fB\-MT\fR option will set the target to be exactly the string you
446specify. If you want multiple targets, you can specify them as a single
447argument to \fB\-MT\fR, or use multiple \fB\-MT\fR options.
448.Sp
449For example, \fB\-MT\ '$(objpfx)foo.o'\fR might give
450.Sp
451.Vb 1
452\& $(objpfx)foo.o: foo.c
453.Ve
454.IP "\fB\-MQ\fR \fItarget\fR" 4
455.IX Item "-MQ target"
456Same as \fB\-MT\fR, but it quotes any characters which are special to
457Make. \fB\-MQ\ '$(objpfx)foo.o'\fR gives
458.Sp
459.Vb 1
460\& $$(objpfx)foo.o: foo.c
461.Ve
462.Sp
463The default target is automatically quoted, as if it were given with
464\&\fB\-MQ\fR.
465.IP "\fB\-MD\fR" 4
466.IX Item "-MD"
467\&\fB\-MD\fR is equivalent to \fB\-M \-MF\fR \fIfile\fR, except that
468\&\fB\-E\fR is not implied. The driver determines \fIfile\fR based on
469whether an \fB\-o\fR option is given. If it is, the driver uses its
470argument but with a suffix of \fI.d\fR, otherwise it take the
471basename of the input file and applies a \fI.d\fR suffix.
472.Sp
473If \fB\-MD\fR is used in conjunction with \fB\-E\fR, any
474\&\fB\-o\fR switch is understood to specify the dependency output file
475(but \f(CW@pxref\fR{dashMF,,\-MF}), but if used without \fB\-E\fR, each \fB\-o\fR
476is understood to specify a target object file.
477.Sp
478Since \fB\-E\fR is not implied, \fB\-MD\fR can be used to generate
479a dependency output file as a side-effect of the compilation process.
480.IP "\fB\-MMD\fR" 4
481.IX Item "-MMD"
482Like \fB\-MD\fR except mention only user header files, not system
483\&\-header files.
484.IP "\fB\-x c\fR" 4
485.IX Item "-x c"
486.PD 0
487.IP "\fB\-x c++\fR" 4
488.IX Item "-x c++"
489.IP "\fB\-x objective-c\fR" 4
490.IX Item "-x objective-c"
491.IP "\fB\-x assembler-with-cpp\fR" 4
492.IX Item "-x assembler-with-cpp"
493.PD
494Specify the source language: C, \*(C+, Objective\-C, or assembly. This has
495nothing to do with standards conformance or extensions; it merely
496selects which base syntax to expect. If you give none of these options,
497cpp will deduce the language from the extension of the source file:
498\&\fB.c\fR, \fB.cc\fR, \fB.m\fR, or \fB.S\fR. Some other common
499extensions for \*(C+ and assembly are also recognized. If cpp does not
500recognize the extension, it will treat the file as C; this is the most
501generic mode.
502.Sp
503\&\fBNote:\fR Previous versions of cpp accepted a \fB\-lang\fR option
504which selected both the language and the standards conformance level.
505This option has been removed, because it conflicts with the \fB\-l\fR
506option.
507.IP "\fB\-std=\fR\fIstandard\fR" 4
508.IX Item "-std=standard"
509.PD 0
510.IP "\fB\-ansi\fR" 4
511.IX Item "-ansi"
512.PD
513Specify the standard to which the code should conform. Currently \s-1CPP\s0
514knows about C and \*(C+ standards; others may be added in the future.
515.Sp
516\&\fIstandard\fR
517may be one of:
518.RS 4
519.ie n .IP """iso9899:1990""" 4
520.el .IP "\f(CWiso9899:1990\fR" 4
521.IX Item "iso9899:1990"
522.PD 0
523.ie n .IP """c89""" 4
524.el .IP "\f(CWc89\fR" 4
525.IX Item "c89"
526.PD
527The \s-1ISO\s0 C standard from 1990. \fBc89\fR is the customary shorthand for
528this version of the standard.
529.Sp
530The \fB\-ansi\fR option is equivalent to \fB\-std=c89\fR.
531.ie n .IP """iso9899:199409""" 4
532.el .IP "\f(CWiso9899:199409\fR" 4
533.IX Item "iso9899:199409"
534The 1990 C standard, as amended in 1994.
535.ie n .IP """iso9899:1999""" 4
536.el .IP "\f(CWiso9899:1999\fR" 4
537.IX Item "iso9899:1999"
538.PD 0
539.ie n .IP """c99""" 4
540.el .IP "\f(CWc99\fR" 4
541.IX Item "c99"
542.ie n .IP """iso9899:199x""" 4
543.el .IP "\f(CWiso9899:199x\fR" 4
544.IX Item "iso9899:199x"
545.ie n .IP """c9x""" 4
546.el .IP "\f(CWc9x\fR" 4
547.IX Item "c9x"
548.PD
549The revised \s-1ISO\s0 C standard, published in December 1999. Before
550publication, this was known as C9X.
551.ie n .IP """gnu89""" 4
552.el .IP "\f(CWgnu89\fR" 4
553.IX Item "gnu89"
554The 1990 C standard plus \s-1GNU\s0 extensions. This is the default.
555.ie n .IP """gnu99""" 4
556.el .IP "\f(CWgnu99\fR" 4
557.IX Item "gnu99"
558.PD 0
559.ie n .IP """gnu9x""" 4
560.el .IP "\f(CWgnu9x\fR" 4
561.IX Item "gnu9x"
562.PD
563The 1999 C standard plus \s-1GNU\s0 extensions.
564.ie n .IP """c++98""" 4
565.el .IP "\f(CWc++98\fR" 4
566.IX Item "c++98"
567The 1998 \s-1ISO\s0 \*(C+ standard plus amendments.
568.ie n .IP """gnu++98""" 4
569.el .IP "\f(CWgnu++98\fR" 4
570.IX Item "gnu++98"
571The same as \fB\-std=c++98\fR plus \s-1GNU\s0 extensions. This is the
572default for \*(C+ code.
573.RE
574.RS 4
575.RE
576.IP "\fB\-I\-\fR" 4
577.IX Item "-I-"
578Split the include path. Any directories specified with \fB\-I\fR
579options before \fB\-I\-\fR are searched only for headers requested with
580\&\f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR; they are not searched for
581\&\f(CW\*(C`#include\ <\f(CIfile\f(CW>\*(C'\fR. If additional directories are
582specified with \fB\-I\fR options after the \fB\-I\-\fR, those
583directories are searched for all \fB#include\fR directives.
584.Sp
585In addition, \fB\-I\-\fR inhibits the use of the directory of the current
586file directory as the first search directory for \f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR.
587.IP "\fB\-nostdinc\fR" 4
588.IX Item "-nostdinc"
589Do not search the standard system directories for header files.
590Only the directories you have specified with \fB\-I\fR options
591(and the directory of the current file, if appropriate) are searched.
592.IP "\fB\-nostdinc++\fR" 4
593.IX Item "-nostdinc++"
594Do not search for header files in the \*(C+\-specific standard directories,
595but do still search the other standard directories. (This option is
596used when building the \*(C+ library.)
597.IP "\fB\-include\fR \fIfile\fR" 4
598.IX Item "-include file"
599Process \fIfile\fR as if \f(CW\*(C`#include "file"\*(C'\fR appeared as the first
600line of the primary source file. However, the first directory searched
601for \fIfile\fR is the preprocessor's working directory \fIinstead of\fR
602the directory containing the main source file. If not found there, it
603is searched for in the remainder of the \f(CW\*(C`#include "..."\*(C'\fR search
604chain as normal.
605.Sp
606If multiple \fB\-include\fR options are given, the files are included
607in the order they appear on the command line.
608.IP "\fB\-imacros\fR \fIfile\fR" 4
609.IX Item "-imacros file"
610Exactly like \fB\-include\fR, except that any output produced by
611scanning \fIfile\fR is thrown away. Macros it defines remain defined.
612This allows you to acquire all the macros from a header without also
613processing its declarations.
614.Sp
615All files specified by \fB\-imacros\fR are processed before all files
616specified by \fB\-include\fR.
617.IP "\fB\-idirafter\fR \fIdir\fR" 4
618.IX Item "-idirafter dir"
619Search \fIdir\fR for header files, but do it \fIafter\fR all
620directories specified with \fB\-I\fR and the standard system directories
621have been exhausted. \fIdir\fR is treated as a system include directory.
622.IP "\fB\-iprefix\fR \fIprefix\fR" 4
623.IX Item "-iprefix prefix"
624Specify \fIprefix\fR as the prefix for subsequent \fB\-iwithprefix\fR
625options. If the prefix represents a directory, you should include the
626final \fB/\fR.
627.IP "\fB\-iwithprefix\fR \fIdir\fR" 4
628.IX Item "-iwithprefix dir"
629.PD 0
630.IP "\fB\-iwithprefixbefore\fR \fIdir\fR" 4
631.IX Item "-iwithprefixbefore dir"
632.PD
633Append \fIdir\fR to the prefix specified previously with
634\&\fB\-iprefix\fR, and add the resulting directory to the include search
635path. \fB\-iwithprefixbefore\fR puts it in the same place \fB\-I\fR
636would; \fB\-iwithprefix\fR puts it where \fB\-idirafter\fR would.
637.IP "\fB\-isystem\fR \fIdir\fR" 4
638.IX Item "-isystem dir"
639Search \fIdir\fR for header files, after all directories specified by
640\&\fB\-I\fR but before the standard system directories. Mark it
641as a system directory, so that it gets the same special treatment as
642is applied to the standard system directories.
643.IP "\fB\-fdollars\-in\-identifiers\fR" 4
644.IX Item "-fdollars-in-identifiers"
645@anchor{fdollars\-in\-identifiers}
646Accept \fB$\fR in identifiers.
647.IP "\fB\-fpreprocessed\fR" 4
648.IX Item "-fpreprocessed"
649Indicate to the preprocessor that the input file has already been
650preprocessed. This suppresses things like macro expansion, trigraph
651conversion, escaped newline splicing, and processing of most directives.
652The preprocessor still recognizes and removes comments, so that you can
653pass a file preprocessed with \fB\-C\fR to the compiler without
654problems. In this mode the integrated preprocessor is little more than
655a tokenizer for the front ends.
656.Sp
657\&\fB\-fpreprocessed\fR is implicit if the input file has one of the
658extensions \fB.i\fR, \fB.ii\fR or \fB.mi\fR. These are the
659extensions that \s-1GCC\s0 uses for preprocessed files created by
660\&\fB\-save\-temps\fR.
661.IP "\fB\-ftabstop=\fR\fIwidth\fR" 4
662.IX Item "-ftabstop=width"
663Set the distance between tab stops. This helps the preprocessor report
664correct column numbers in warnings or errors, even if tabs appear on the
665line. If the value is less than 1 or greater than 100, the option is
666ignored. The default is 8.
667.IP "\fB\-fexec\-charset=\fR\fIcharset\fR" 4
668.IX Item "-fexec-charset=charset"
669Set the execution character set, used for string and character
670constants. The default is \s-1UTF\-8\s0. \fIcharset\fR can be any encoding
671supported by the system's \f(CW\*(C`iconv\*(C'\fR library routine.
672.IP "\fB\-fwide\-exec\-charset=\fR\fIcharset\fR" 4
673.IX Item "-fwide-exec-charset=charset"
674Set the wide execution character set, used for wide string and
675character constants. The default is \s-1UTF\-32\s0 or \s-1UTF\-16\s0, whichever
676corresponds to the width of \f(CW\*(C`wchar_t\*(C'\fR. As with
677\&\fB\-ftarget\-charset\fR, \fIcharset\fR can be any encoding supported
678by the system's \f(CW\*(C`iconv\*(C'\fR library routine; however, you will have
679problems with encodings that do not fit exactly in \f(CW\*(C`wchar_t\*(C'\fR.
680.IP "\fB\-finput\-charset=\fR\fIcharset\fR" 4
681.IX Item "-finput-charset=charset"
682Set the input character set, used for translation from the character
683set of the input file to the source character set used by \s-1GCC\s0. If the
684locale does not specify, or \s-1GCC\s0 cannot get this information from the
685locale, the default is \s-1UTF\-8\s0. This can be overridden by either the locale
686or this command line option. Currently the command line option takes
687precedence if there's a conflict. \fIcharset\fR can be any encoding
688supported by the system's \f(CW\*(C`iconv\*(C'\fR library routine.
689.IP "\fB\-fworking\-directory\fR" 4
690.IX Item "-fworking-directory"
691Enable generation of linemarkers in the preprocessor output that will
692let the compiler know the current working directory at the time of
693preprocessing. When this option is enabled, the preprocessor will
694emit, after the initial linemarker, a second linemarker with the
695current working directory followed by two slashes. \s-1GCC\s0 will use this
696directory, when it's present in the preprocessed input, as the
697directory emitted as the current working directory in some debugging
698information formats. This option is implicitly enabled if debugging
699information is enabled, but this can be inhibited with the negated
700form \fB\-fno\-working\-directory\fR. If the \fB\-P\fR flag is
701present in the command line, this option has no effect, since no
702\&\f(CW\*(C`#line\*(C'\fR directives are emitted whatsoever.
703.IP "\fB\-fno\-show\-column\fR" 4
704.IX Item "-fno-show-column"
705Do not print column numbers in diagnostics. This may be necessary if
706diagnostics are being scanned by a program that does not understand the
707column numbers, such as \fBdejagnu\fR.
708.IP "\fB\-A\fR \fIpredicate\fR\fB=\fR\fIanswer\fR" 4
709.IX Item "-A predicate=answer"
710Make an assertion with the predicate \fIpredicate\fR and answer
711\&\fIanswer\fR. This form is preferred to the older form \fB\-A\fR
712\&\fIpredicate\fR\fB(\fR\fIanswer\fR\fB)\fR, which is still supported, because
713it does not use shell special characters.
714.IP "\fB\-A \-\fR\fIpredicate\fR\fB=\fR\fIanswer\fR" 4
715.IX Item "-A -predicate=answer"
716Cancel an assertion with the predicate \fIpredicate\fR and answer
717\&\fIanswer\fR.
718.IP "\fB\-dCHARS\fR" 4
719.IX Item "-dCHARS"
720\&\fI\s-1CHARS\s0\fR is a sequence of one or more of the following characters,
721and must not be preceded by a space. Other characters are interpreted
722by the compiler proper, or reserved for future versions of \s-1GCC\s0, and so
723are silently ignored. If you specify characters whose behavior
724conflicts, the result is undefined.
725.RS 4
726.IP "\fBM\fR" 4
727.IX Item "M"
728Instead of the normal output, generate a list of \fB#define\fR
729directives for all the macros defined during the execution of the
730preprocessor, including predefined macros. This gives you a way of
731finding out what is predefined in your version of the preprocessor.
732Assuming you have no file \fIfoo.h\fR, the command
733.Sp
734.Vb 1
735\& touch foo.h; cpp -dM foo.h
736.Ve
737.Sp
738will show all the predefined macros.
739.IP "\fBD\fR" 4
740.IX Item "D"
741Like \fBM\fR except in two respects: it does \fInot\fR include the
742predefined macros, and it outputs \fIboth\fR the \fB#define\fR
743directives and the result of preprocessing. Both kinds of output go to
744the standard output file.
745.IP "\fBN\fR" 4
746.IX Item "N"
747Like \fBD\fR, but emit only the macro names, not their expansions.
748.IP "\fBI\fR" 4
749.IX Item "I"
750Output \fB#include\fR directives in addition to the result of
751preprocessing.
752.RE
753.RS 4
754.RE
755.IP "\fB\-P\fR" 4
756.IX Item "-P"
757Inhibit generation of linemarkers in the output from the preprocessor.
758This might be useful when running the preprocessor on something that is
759not C code, and will be sent to a program which might be confused by the
760linemarkers.
761.IP "\fB\-C\fR" 4
762.IX Item "-C"
763Do not discard comments. All comments are passed through to the output
764file, except for comments in processed directives, which are deleted
765along with the directive.
766.Sp
767You should be prepared for side effects when using \fB\-C\fR; it
768causes the preprocessor to treat comments as tokens in their own right.
769For example, comments appearing at the start of what would be a
770directive line have the effect of turning that line into an ordinary
771source line, since the first token on the line is no longer a \fB#\fR.
772.IP "\fB\-CC\fR" 4
773.IX Item "-CC"
774Do not discard comments, including during macro expansion. This is
775like \fB\-C\fR, except that comments contained within macros are
776also passed through to the output file where the macro is expanded.
777.Sp
778In addition to the side-effects of the \fB\-C\fR option, the
779\&\fB\-CC\fR option causes all \*(C+\-style comments inside a macro
780to be converted to C\-style comments. This is to prevent later use
781of that macro from inadvertently commenting out the remainder of
782the source line.
783.Sp
784The \fB\-CC\fR option is generally used to support lint comments.
785.IP "\fB\-traditional\-cpp\fR" 4
786.IX Item "-traditional-cpp"
787Try to imitate the behavior of old-fashioned C preprocessors, as
788opposed to \s-1ISO\s0 C preprocessors.
789.IP "\fB\-trigraphs\fR" 4
790.IX Item "-trigraphs"
791Process trigraph sequences.
792.IP "\fB\-remap\fR" 4
793.IX Item "-remap"
794Enable special code to work around file systems which only permit very
795short file names, such as \s-1MS\-DOS\s0.
796.IP "\fB\-\-help\fR" 4
797.IX Item "--help"
798.PD 0
799.IP "\fB\-\-target\-help\fR" 4
800.IX Item "--target-help"
801.PD
802Print text describing all the command line options instead of
803preprocessing anything.
804.IP "\fB\-v\fR" 4
805.IX Item "-v"
806Verbose mode. Print out \s-1GNU\s0 \s-1CPP\s0's version number at the beginning of
807execution, and report the final form of the include path.
808.IP "\fB\-H\fR" 4
809.IX Item "-H"
810Print the name of each header file used, in addition to other normal
811activities. Each name is indented to show how deep in the
812\&\fB#include\fR stack it is. Precompiled header files are also
813printed, even if they are found to be invalid; an invalid precompiled
814header file is printed with \fB...x\fR and a valid one with \fB...!\fR .
815.IP "\fB\-version\fR" 4
816.IX Item "-version"
817.PD 0
818.IP "\fB\-\-version\fR" 4
819.IX Item "--version"
820.PD
821Print out \s-1GNU\s0 \s-1CPP\s0's version number. With one dash, proceed to
822preprocess as normal. With two dashes, exit immediately.
823.SH "ENVIRONMENT"
824.IX Header "ENVIRONMENT"
825This section describes the environment variables that affect how \s-1CPP\s0
826operates. You can use them to specify directories or prefixes to use
827when searching for include files, or to control dependency output.
828.PP
829Note that you can also specify places to search using options such as
830\&\fB\-I\fR, and control dependency output with options like
831\&\fB\-M\fR. These take precedence over
832environment variables, which in turn take precedence over the
833configuration of \s-1GCC\s0.
834.IP "\fB\s-1CPATH\s0\fR" 4
835.IX Item "CPATH"
836.PD 0
837.IP "\fBC_INCLUDE_PATH\fR" 4
838.IX Item "C_INCLUDE_PATH"
839.IP "\fB\s-1CPLUS_INCLUDE_PATH\s0\fR" 4
840.IX Item "CPLUS_INCLUDE_PATH"
841.IP "\fB\s-1OBJC_INCLUDE_PATH\s0\fR" 4
842.IX Item "OBJC_INCLUDE_PATH"
843.PD
844Each variable's value is a list of directories separated by a special
845character, much like \fB\s-1PATH\s0\fR, in which to look for header files.
846The special character, \f(CW\*(C`PATH_SEPARATOR\*(C'\fR, is target-dependent and
847determined at \s-1GCC\s0 build time. For Microsoft Windows-based targets it is a
848semicolon, and for almost all other targets it is a colon.
849.Sp
850\&\fB\s-1CPATH\s0\fR specifies a list of directories to be searched as if
851specified with \fB\-I\fR, but after any paths given with \fB\-I\fR
852options on the command line. This environment variable is used
853regardless of which language is being preprocessed.
854.Sp
855The remaining environment variables apply only when preprocessing the
856particular language indicated. Each specifies a list of directories
857to be searched as if specified with \fB\-isystem\fR, but after any
858paths given with \fB\-isystem\fR options on the command line.
859.Sp
860In all these variables, an empty element instructs the compiler to
861search its current working directory. Empty elements can appear at the
862beginning or end of a path. For instance, if the value of
863\&\fB\s-1CPATH\s0\fR is \f(CW\*(C`:/special/include\*(C'\fR, that has the same
864effect as \fB\-I.\ \-I/special/include\fR.
865.IP "\fB\s-1DEPENDENCIES_OUTPUT\s0\fR" 4
866.IX Item "DEPENDENCIES_OUTPUT"
867If this variable is set, its value specifies how to output
868dependencies for Make based on the non-system header files processed
869by the compiler. System header files are ignored in the dependency
870output.
871.Sp
872The value of \fB\s-1DEPENDENCIES_OUTPUT\s0\fR can be just a file name, in
873which case the Make rules are written to that file, guessing the target
874name from the source file name. Or the value can have the form
875\&\fIfile\fR\fB \fR\fItarget\fR, in which case the rules are written to
876file \fIfile\fR using \fItarget\fR as the target name.
877.Sp
878In other words, this environment variable is equivalent to combining
879the options \fB\-MM\fR and \fB\-MF\fR,
880with an optional \fB\-MT\fR switch too.
881.IP "\fB\s-1SUNPRO_DEPENDENCIES\s0\fR" 4
882.IX Item "SUNPRO_DEPENDENCIES"
883This variable is the same as \fB\s-1DEPENDENCIES_OUTPUT\s0\fR (see above),
884except that system header files are not ignored, so it implies
885\&\fB\-M\fR rather than \fB\-MM\fR. However, the dependence on the
886main input file is omitted.
887.SH "SEE ALSO"
888.IX Header "SEE ALSO"
889\&\fIgpl\fR\|(7), \fIgfdl\fR\|(7), \fIfsf\-funding\fR\|(7),
890\&\fIgcc\fR\|(1), \fIas\fR\|(1), \fIld\fR\|(1), and the Info entries for \fIcpp\fR, \fIgcc\fR, and
891\&\fIbinutils\fR.
892.SH "COPYRIGHT"
893.IX Header "COPYRIGHT"
894Copyright (c) 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996,
8951997, 1998, 1999, 2000, 2001, 2002, 2003, 2004
896Free Software Foundation, Inc.
897.PP
898Permission is granted to copy, distribute and/or modify this document
899under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.1 or
900any later version published by the Free Software Foundation. A copy of
901the license is included in the
902man page \fIgfdl\fR\|(7).
903This manual contains no Invariant Sections. The Front-Cover Texts are
904(a) (see below), and the Back-Cover Texts are (b) (see below).
905.PP
906(a) The \s-1FSF\s0's Front-Cover Text is:
907.PP
908.Vb 1
909\& A GNU Manual
910.Ve
911.PP
912(b) The \s-1FSF\s0's Back-Cover Text is:
913.PP
914.Vb 3
915\& You have freedom to copy and modify this GNU Manual, like GNU
916\& software. Copies published by the Free Software Foundation raise
917\& funds for GNU development.
918.Ve