CPP(1) GNU CPP(1) NNAAMMEE cpp - The C Preprocessor SSYYNNOOPPSSIISS cpp [--DD_m_a_c_r_o[=_d_e_f_n]...] [--UU_m_a_c_r_o] [--II_d_i_r...] [--iiqquuoottee_d_i_r...] [--WW_w_a_r_n...] [--MM|--MMMM] [--MMGG] [--MMFF _f_i_l_e_n_a_m_e] [--MMPP] [--MMQQ _t_a_r_g_e_t...] [--MMTT _t_a_r_g_e_t...] [--PP] [--ffnnoo--wwoorrkkiinngg--ddiirreeccttoorryy] [--xx _l_a_n_g_u_a_g_e] [--ssttdd==_s_t_a_n_d_a_r_d] _i_n_f_i_l_e _o_u_t_f_i_l_e Only the most useful options are listed here; see below for the remainder. DDEESSCCRRIIPPTTIIOONN The C preprocessor, often known as _c_p_p, is a _m_a_c_r_o _p_r_o_c_e_s_s_o_r that is used automatically by the C compiler to transform your program before compilation. It is called a macro processor because it allows you to define _m_a_c_r_o_s, which are brief abbreviations for longer constructs. The C preprocessor is intended to be used only with C, C++, and Objective-C source code. In the past, it has been abused as a general text processor. It will choke on input which does not obey C's lexical rules. For example, apostrophes will be interpreted as the beginning of character constants, and cause errors. Also, you cannot rely on it preserving characteristics of the input which are not significant to C-family languages. If a Makefile is preprocessed, all the hard tabs will be removed, and the Makefile will not work. Having said that, you can often get away with using cpp on things which are not C. Other Algol-ish programming languages are often safe (Pascal, Ada, etc.) So is assembly, with caution. --ttrraaddiittiioonnaall--ccpppp mode preserves more white space, and is otherwise more permissive. Many of the problems can be avoided by writing C or C++ style comments instead of native language comments, and keeping macros simple. Wherever possible, you should use a preprocessor geared to the language you are writing in. Modern versions of the GNU assembler have macro facilities. Most high level programming languages have their own conditional compilation and inclusion mechanism. If all else fails, try a true general text processor, such as GNU M4. C preprocessors vary in some details. This manual discusses the GNU C preprocessor, which provides a small superset of the features of ISO Standard C. In its default mode, the GNU C preprocessor does not do a few things required by the standard. These are features which are rarely, if ever, used, and may cause surprising changes to the meaning of a program which does not expect them. To get strict ISO Standard C, you should use the --ssttdd==cc9900, --ssttdd==cc9999 or --ssttdd==cc1111 options, depending on which version of the standard you want. To get all the mandatory diagnostics, you must also use --ppeeddaannttiicc. This manual describes the behavior of the ISO preprocessor. To minimize gratuitous differences, where the ISO preprocessor's behavior does not conflict with traditional semantics, the traditional preprocessor should behave the same way. The various differences that do exist are detailed in the section TTrraaddiittiioonnaall MMooddee. For clarity, unless noted otherwise, references to CCPPPP in this manual refer to GNU CPP. OOPPTTIIOONNSS The C preprocessor expects two file names as arguments, _i_n_f_i_l_e and _o_u_t_f_i_l_e. The preprocessor reads _i_n_f_i_l_e together with any other files it specifies with ##iinncclluuddee. All the output generated by the combined input files is written in _o_u_t_f_i_l_e. Either _i_n_f_i_l_e or _o_u_t_f_i_l_e may be --, which as _i_n_f_i_l_e means to read from standard input and as _o_u_t_f_i_l_e means to write to standard output. Also, if either file is omitted, it means the same as if -- had been specified for that file. Unless otherwise noted, or the option ends in ==, all options which take an argument may have that argument appear either immediately after the option, or with a space between option and argument: --IIffoooo and --II ffoooo have the same effect. Many options have multi-letter names; therefore multiple single-letter options may _n_o_t be grouped: --ddMM is very different from --dd --MM. --DD _n_a_m_e Predefine _n_a_m_e as a macro, with definition 1. --DD _n_a_m_e==_d_e_f_i_n_i_t_i_o_n The contents of _d_e_f_i_n_i_t_i_o_n are tokenized and processed as if they appeared during translation phase three in a ##ddeeffiinnee directive. In particular, the definition will be truncated by embedded newline characters. If you are invoking the preprocessor from a shell or shell-like program you may need to use the shell's quoting syntax to protect characters such as spaces that have a meaning in the shell syntax. If you wish to define a function-like macro on the command line, write its argument list with surrounding parentheses before the equals sign (if any). Parentheses are meaningful to most shells, so you will need to quote the option. With sshh and ccsshh, --DD''_n_a_m_e((_a_r_g_s_._._.))==_d_e_f_i_n_i_t_i_o_n'' works. --DD and --UU options are processed in the order they are given on the command line. All --iimmaaccrrooss _f_i_l_e and --iinncclluuddee _f_i_l_e options are processed after all --DD and --UU options. --UU _n_a_m_e Cancel any previous definition of _n_a_m_e, either built in or provided with a --DD option. --uunnddeeff Do not predefine any system-specific or GCC-specific macros. The standard predefined macros remain defined. --II _d_i_r Add the directory _d_i_r to the list of directories to be searched for header files. Directories named by --II are searched before the standard system include directories. If the directory _d_i_r is a standard system include directory, the option is ignored to ensure that the default search order for system directories and the special treatment of system headers are not defeated . If _d_i_r begins with "=", then the "=" will be replaced by the sysroot prefix; see ----ssyyssrroooott and --iissyyssrroooott. --oo _f_i_l_e Write output to _f_i_l_e. This is the same as specifying _f_i_l_e as the second non-option argument to ccpppp. ggcccc has a different interpretation of a second non-option argument, so you must use --oo to specify the output file. --WWaallll Turns on all optional warnings which are desirable for normal code. At present this is --WWccoommmmeenntt, --WWttrriiggrraapphhss, --WWmmuullttiicchhaarr and a warning about integer promotion causing a change of sign in "#if" expressions. Note that many of the preprocessor's warnings are on by default and have no options to control them. --WWccoommmmeenntt --WWccoommmmeennttss Warn whenever a comment-start sequence //** appears in a //** comment, or whenever a backslash-newline appears in a //// comment. (Both forms have the same effect.) --WWttrriiggrraapphhss Most trigraphs in comments cannot affect the meaning of the program. However, a trigraph that would form an escaped newline (????// at the end of a line) can, by changing where the comment begins or ends. Therefore, only trigraphs that would form escaped newlines produce warnings inside a comment. This option is implied by --WWaallll. If --WWaallll is not given, this option is still enabled unless trigraphs are enabled. To get trigraph conversion without warnings, but get the other --WWaallll warnings, use --ttrriiggrraapphhss --WWaallll --WWnnoo--ttrriiggrraapphhss. --WWttrraaddiittiioonnaall Warn about certain constructs that behave differently in traditional and ISO C. Also warn about ISO C constructs that have no traditional C equivalent, and problematic constructs which should be avoided. --WWuunnddeeff Warn whenever an identifier which is not a macro is encountered in an ##iiff directive, outside of ddeeffiinneedd. Such identifiers are replaced with zero. --WWuunnuusseedd--mmaaccrrooss Warn about macros defined in the main file that are unused. A macro is _u_s_e_d if it is expanded or tested for existence at least once. The preprocessor will also warn if the macro has not been used at the time it is redefined or undefined. Built-in macros, macros defined on the command line, and macros defined in include files are not warned about. _N_o_t_e_: If a macro is actually used, but only used in skipped conditional blocks, then CPP will report it as unused. To avoid the warning in such a case, you might improve the scope of the macro's definition by, for example, moving it into the first skipped block. Alternatively, you could provide a dummy use with something like: #if defined the_macro_causing_the_warning #endif --WWeennddiiff--llaabbeellss Warn whenever an ##eellssee or an ##eennddiiff are followed by text. This usually happens in code of the form #if FOO ... #else FOO ... #endif FOO The second and third "FOO" should be in comments, but often are not in older programs. This warning is on by default. --WWeerrrroorr Make all warnings into hard errors. Source code which triggers warnings will be rejected. --WWssyysstteemm--hheeaaddeerrss Issue warnings for code in system headers. These are normally unhelpful in finding bugs in your own code, therefore suppressed. If you are responsible for the system library, you may want to see them. --ww Suppress all warnings, including those which GNU CPP issues by default. --ppeeddaannttiicc Issue all the mandatory diagnostics listed in the C standard. Some of them are left out by default, since they trigger frequently on harmless code. --ppeeddaannttiicc--eerrrroorrss Issue all the mandatory diagnostics, and make all mandatory diagnostics into errors. This includes mandatory diagnostics that GCC issues without --ppeeddaannttiicc but treats as warnings. --MM Instead of outputting the result of preprocessing, output a rule suitable for mmaakkee describing the dependencies of the main source file. The preprocessor outputs one mmaakkee rule containing the object file name for that source file, a colon, and the names of all the included files, including those coming from --iinncclluuddee or --iimmaaccrrooss command line options. Unless specified explicitly (with --MMTT or --MMQQ), the object file name consists of the name of the source file with any suffix replaced with object file suffix and with any leading directory parts removed. If there are many included files then the rule is split into several lines using \\-newline. The rule has no commands. This option does not suppress the preprocessor's debug output, such as --ddMM. To avoid mixing such debug output with the dependency rules you should explicitly specify the dependency output file with --MMFF, or use an environment variable like DDEEPPEENNDDEENNCCIIEESS__OOUUTTPPUUTT. Debug output will still be sent to the regular output stream as normal. Passing --MM to the driver implies --EE, and suppresses warnings with an implicit --ww. --MMMM Like --MM but do not mention header files that are found in system header directories, nor header files that are included, directly or indirectly, from such a header. This implies that the choice of angle brackets or double quotes in an ##iinncclluuddee directive does not in itself determine whether that header will appear in --MMMM dependency output. This is a slight change in semantics from GCC versions 3.0 and earlier. --MMFF _f_i_l_e When used with --MM or --MMMM, specifies a file to write the dependencies to. If no --MMFF switch is given the preprocessor sends the rules to the same place it would have sent preprocessed output. When used with the driver options --MMDD or --MMMMDD, --MMFF overrides the default dependency output file. --MMGG In conjunction with an option such as --MM requesting dependency generation, --MMGG assumes missing header files are generated files and adds them to the dependency list without raising an error. The dependency filename is taken directly from the "#include" directive without prepending any path. --MMGG also suppresses preprocessed output, as a missing header file renders this useless. This feature is used in automatic updating of makefiles. --MMPP This option instructs CPP to add a phony target for each dependency other than the main file, causing each to depend on nothing. These dummy rules work around errors mmaakkee gives if you remove header files without updating the _M_a_k_e_f_i_l_e to match. This is typical output: test.o: test.c test.h test.h: --MMTT _t_a_r_g_e_t Change the target of the rule emitted by dependency generation. By default CPP takes the name of the main input file, deletes any directory components and any file suffix such as ..cc, and appends the platform's usual object suffix. The result is the target. An --MMTT option will set the target to be exactly the string you specify. If you want multiple targets, you can specify them as a single argument to --MMTT, or use multiple --MMTT options. For example, --MMTT ''$$((oobbjjppffxx))ffoooo..oo'' might give $(objpfx)foo.o: foo.c --MMQQ _t_a_r_g_e_t Same as --MMTT, but it quotes any characters which are special to Make. --MMQQ ''$$((oobbjjppffxx))ffoooo..oo'' gives $$(objpfx)foo.o: foo.c The default target is automatically quoted, as if it were given with --MMQQ. --MMDD --MMDD is equivalent to --MM --MMFF _f_i_l_e, except that --EE is not implied. The driver determines _f_i_l_e based on whether an --oo option is given. If it is, the driver uses its argument but with a suffix of _._d, otherwise it takes the name of the input file, removes any directory components and suffix, and applies a _._d suffix. If --MMDD is used in conjunction with --EE, any --oo switch is understood to specify the dependency output file, but if used without --EE, each --oo is understood to specify a target object file. Since --EE is not implied, --MMDD can be used to generate a dependency output file as a side-effect of the compilation process. --MMMMDD Like --MMDD except mention only user header files, not system header files. --xx cc --xx cc++++ --xx oobbjjeeccttiivvee--cc --xx aasssseemmbblleerr--wwiitthh--ccpppp Specify the source language: C, C++, Objective-C, or assembly. This has nothing to do with standards conformance or extensions; it merely selects which base syntax to expect. If you give none of these options, cpp will deduce the language from the extension of the source file: ..cc, ..cccc, ..mm, or ..SS. Some other common extensions for C++ and assembly are also recognized. If cpp does not recognize the extension, it will treat the file as C; this is the most generic mode. _N_o_t_e_: Previous versions of cpp accepted a --llaanngg option which selected both the language and the standards conformance level. This option has been removed, because it conflicts with the --ll option. --ssttdd==_s_t_a_n_d_a_r_d --aannssii Specify the standard to which the code should conform. Currently CPP knows about C and C++ standards; others may be added in the future. _s_t_a_n_d_a_r_d may be one of: "c90" "c89" "iso9899:1990" The ISO C standard from 1990. cc9900 is the customary shorthand for this version of the standard. The --aannssii option is equivalent to --ssttdd==cc9900. "iso9899:199409" The 1990 C standard, as amended in 1994. "iso9899:1999" "c99" "iso9899:199x" "c9x" The revised ISO C standard, published in December 1999. Before publication, this was known as C9X. "iso9899:2011" "c11" "c1x" The revised ISO C standard, published in December 2011. Before publication, this was known as C1X. "gnu90" "gnu89" The 1990 C standard plus GNU extensions. This is the default. "gnu99" "gnu9x" The 1999 C standard plus GNU extensions. "gnu11" "gnu1x" The 2011 C standard plus GNU extensions. "c++98" The 1998 ISO C++ standard plus amendments. "gnu++98" The same as --ssttdd==cc++++9988 plus GNU extensions. This is the default for C++ code. --II-- Split the include path. Any directories specified with --II options before --II-- are searched only for headers requested with "#include "_f_i_l_e_"_"; they are not searched for "#include <_f_i_l_e_>_". If additional directories are specified with --II options after the --II--, those directories are searched for all ##iinncclluuddee directives. In addition, --II-- inhibits the use of the directory of the current file directory as the first search directory for "#include "_f_i_l_e_"_". This option has been deprecated. --nnoossttddiinncc Do not search the standard system directories for header files. Only the directories you have specified with --II options (and the directory of the current file, if appropriate) are searched. --nnoossttddiinncc++++ Do not search for header files in the C++-specific standard directories, but do still search the other standard directories. (This option is used when building the C++ library.) --iinncclluuddee _f_i_l_e Process _f_i_l_e as if "#include "file"" appeared as the first line of the primary source file. However, the first directory searched for _f_i_l_e is the preprocessor's working directory _i_n_s_t_e_a_d _o_f the directory containing the main source file. If not found there, it is searched for in the remainder of the "#include "..."" search chain as normal. If multiple --iinncclluuddee options are given, the files are included in the order they appear on the command line. --iimmaaccrrooss _f_i_l_e Exactly like --iinncclluuddee, except that any output produced by scanning _f_i_l_e is thrown away. Macros it defines remain defined. This allows you to acquire all the macros from a header without also processing its declarations. All files specified by --iimmaaccrrooss are processed before all files specified by --iinncclluuddee. --iiddiirraafftteerr _d_i_r Search _d_i_r for header files, but do it _a_f_t_e_r all directories specified with --II and the standard system directories have been exhausted. _d_i_r is treated as a system include directory. If _d_i_r begins with "=", then the "=" will be replaced by the sysroot prefix; see ----ssyyssrroooott and --iissyyssrroooott. --iipprreeffiixx _p_r_e_f_i_x Specify _p_r_e_f_i_x as the prefix for subsequent --iiwwiitthhpprreeffiixx options. If the prefix represents a directory, you should include the final //. --iiwwiitthhpprreeffiixx _d_i_r --iiwwiitthhpprreeffiixxbbeeffoorree _d_i_r Append _d_i_r to the prefix specified previously with --iipprreeffiixx, and add the resulting directory to the include search path. --iiwwiitthhpprreeffiixxbbeeffoorree puts it in the same place --II would; --iiwwiitthhpprreeffiixx puts it where --iiddiirraafftteerr would. --iissyyssrroooott _d_i_r This option is like the ----ssyyssrroooott option, but applies only to header files (except for Darwin targets, where it applies to both header files and libraries). See the ----ssyyssrroooott option for more information. --iimmuullttiilliibb _d_i_r Use _d_i_r as a subdirectory of the directory containing target- specific C++ headers. --iissyysstteemm _d_i_r Search _d_i_r for header files, after all directories specified by --II but before the standard system directories. Mark it as a system directory, so that it gets the same special treatment as is applied to the standard system directories. If _d_i_r begins with "=", then the "=" will be replaced by the sysroot prefix; see ----ssyyssrroooott and --iissyyssrroooott. --iiqquuoottee _d_i_r Search _d_i_r only for header files requested with "#include "_f_i_l_e_"_"; they are not searched for "#include <_f_i_l_e_>_", before all directories specified by --II and before the standard system directories. If _d_i_r begins with "=", then the "=" will be replaced by the sysroot prefix; see ----ssyyssrroooott and --iissyyssrroooott. --ffddiirreeccttiivveess--oonnllyy When preprocessing, handle directives, but do not expand macros. The option's behavior depends on the --EE and --ffpprreepprroocceesssseedd options. With --EE, preprocessing is limited to the handling of directives such as "#define", "#ifdef", and "#error". Other preprocessor operations, such as macro expansion and trigraph conversion are not performed. In addition, the --ddDD option is implicitly enabled. With --ffpprreepprroocceesssseedd, predefinition of command line and most builtin macros is disabled. Macros such as "__LINE__", which are contextually dependent, are handled normally. This enables compilation of files previously preprocessed with "-E -fdirectives-only". With both --EE and --ffpprreepprroocceesssseedd, the rules for --ffpprreepprroocceesssseedd take precedence. This enables full preprocessing of files previously preprocessed with "-E -fdirectives-only". --ffddoollllaarrss--iinn--iiddeennttiiffiieerrss Accept $$ in identifiers. --ffeexxtteennddeedd--iiddeennttiiffiieerrss Accept universal character names in identifiers. This option is experimental; in a future version of GCC, it will be enabled by default for C99 and C++. --ffnnoo--ccaannoonniiccaall--ssyysstteemm--hheeaaddeerrss When preprocessing, do not shorten system header paths with canonicalization. --ffpprreepprroocceesssseedd Indicate to the preprocessor that the input file has already been preprocessed. This suppresses things like macro expansion, trigraph conversion, escaped newline splicing, and processing of most directives. The preprocessor still recognizes and removes comments, so that you can pass a file preprocessed with --CC to the compiler without problems. In this mode the integrated preprocessor is little more than a tokenizer for the front ends. --ffpprreepprroocceesssseedd is implicit if the input file has one of the extensions ..ii, ..iiii or ..mmii. These are the extensions that GCC uses for preprocessed files created by --ssaavvee--tteemmppss. --ffttaabbssttoopp==_w_i_d_t_h Set the distance between tab stops. This helps the preprocessor report correct column numbers in warnings or errors, even if tabs appear on the line. If the value is less than 1 or greater than 100, the option is ignored. The default is 8. --ffddeebbuugg--ccpppp This option is only useful for debugging GCC. When used with --EE, dumps debugging information about location maps. Every token in the output is preceded by the dump of the map its location belongs to. The dump of the map holding the location of a token would be: {"P":F;"F":F;"L":;"C":;"S":;"M":;"E":,"loc":} When used without --EE, this option has no effect. --ffttrraacckk--mmaaccrroo--eexxppaannssiioonn[==_l_e_v_e_l] Track locations of tokens across macro expansions. This allows the compiler to emit diagnostic about the current macro expansion stack when a compilation error occurs in a macro expansion. Using this option makes the preprocessor and the compiler consume more memory. The _l_e_v_e_l parameter can be used to choose the level of precision of token location tracking thus decreasing the memory consumption if necessary. Value 00 of _l_e_v_e_l de-activates this option just as if no --ffttrraacckk--mmaaccrroo--eexxppaannssiioonn was present on the command line. Value 11 tracks tokens locations in a degraded mode for the sake of minimal memory overhead. In this mode all tokens resulting from the expansion of an argument of a function-like macro have the same location. Value 22 tracks tokens locations completely. This value is the most memory hungry. When this option is given no argument, the default parameter value is 22. Note that -ftrack-macro-expansion=2 is activated by default. --ffeexxeecc--cchhaarrsseett==_c_h_a_r_s_e_t Set the execution character set, used for string and character constants. The default is UTF-8. _c_h_a_r_s_e_t can be any encoding supported by the system's "iconv" library routine. --ffwwiiddee--eexxeecc--cchhaarrsseett==_c_h_a_r_s_e_t Set the wide execution character set, used for wide string and character constants. The default is UTF-32 or UTF-16, whichever corresponds to the width of "wchar_t". As with --ffeexxeecc--cchhaarrsseett, _c_h_a_r_s_e_t can be any encoding supported by the system's "iconv" library routine; however, you will have problems with encodings that do not fit exactly in "wchar_t". --ffiinnppuutt--cchhaarrsseett==_c_h_a_r_s_e_t Set the input character set, used for translation from the character set of the input file to the source character set used by GCC. If the locale does not specify, or GCC cannot get this information from the locale, the default is UTF-8. This can be overridden by either the locale or this command line option. Currently the command line option takes precedence if there's a conflict. _c_h_a_r_s_e_t can be any encoding supported by the system's "iconv" library routine. --ffwwoorrkkiinngg--ddiirreeccttoorryy Enable generation of linemarkers in the preprocessor output that will let the compiler know the current working directory at the time of preprocessing. When this option is enabled, the preprocessor will emit, after the initial linemarker, a second linemarker with the current working directory followed by two slashes. GCC will use this directory, when it's present in the preprocessed input, as the directory emitted as the current working directory in some debugging information formats. This option is implicitly enabled if debugging information is enabled, but this can be inhibited with the negated form --ffnnoo--wwoorrkkiinngg--ddiirreeccttoorryy. If the --PP flag is present in the command line, this option has no effect, since no "#line" directives are emitted whatsoever. --ffnnoo--sshhooww--ccoolluummnn Do not print column numbers in diagnostics. This may be necessary if diagnostics are being scanned by a program that does not understand the column numbers, such as ddeejjaaggnnuu. --AA _p_r_e_d_i_c_a_t_e==_a_n_s_w_e_r Make an assertion with the predicate _p_r_e_d_i_c_a_t_e and answer _a_n_s_w_e_r. This form is preferred to the older form --AA _p_r_e_d_i_c_a_t_e((_a_n_s_w_e_r)), which is still supported, because it does not use shell special characters. --AA --_p_r_e_d_i_c_a_t_e==_a_n_s_w_e_r Cancel an assertion with the predicate _p_r_e_d_i_c_a_t_e and answer _a_n_s_w_e_r. --ddCCHHAARRSS _C_H_A_R_S is a sequence of one or more of the following characters, and must not be preceded by a space. Other characters are interpreted by the compiler proper, or reserved for future versions of GCC, and so are silently ignored. If you specify characters whose behavior conflicts, the result is undefined. MM Instead of the normal output, generate a list of ##ddeeffiinnee directives for all the macros defined during the execution of the preprocessor, including predefined macros. This gives you a way of finding out what is predefined in your version of the preprocessor. Assuming you have no file _f_o_o_._h, the command touch foo.h; cpp -dM foo.h will show all the predefined macros. If you use --ddMM without the --EE option, --ddMM is interpreted as a synonym for --ffdduummpp--rrttll--mmaacchh. DD Like MM except in two respects: it does _n_o_t include the predefined macros, and it outputs _b_o_t_h the ##ddeeffiinnee directives and the result of preprocessing. Both kinds of output go to the standard output file. NN Like DD, but emit only the macro names, not their expansions. II Output ##iinncclluuddee directives in addition to the result of preprocessing. UU Like DD except that only macros that are expanded, or whose definedness is tested in preprocessor directives, are output; the output is delayed until the use or test of the macro; and ##uunnddeeff directives are also output for macros tested but undefined at the time. --PP Inhibit generation of linemarkers in the output from the preprocessor. This might be useful when running the preprocessor on something that is not C code, and will be sent to a program which might be confused by the linemarkers. --CC Do not discard comments. All comments are passed through to the output file, except for comments in processed directives, which are deleted along with the directive. You should be prepared for side effects when using --CC; it causes the preprocessor to treat comments as tokens in their own right. For example, comments appearing at the start of what would be a directive line have the effect of turning that line into an ordinary source line, since the first token on the line is no longer a ##. --CCCC Do not discard comments, including during macro expansion. This is like --CC, except that comments contained within macros are also passed through to the output file where the macro is expanded. In addition to the side-effects of the --CC option, the --CCCC option causes all C++-style comments inside a macro to be converted to C-style comments. This is to prevent later use of that macro from inadvertently commenting out the remainder of the source line. The --CCCC option is generally used to support lint comments. --ttrraaddiittiioonnaall--ccpppp Try to imitate the behavior of old-fashioned C preprocessors, as opposed to ISO C preprocessors. --ttrriiggrraapphhss Process trigraph sequences. --rreemmaapp Enable special code to work around file systems which only permit very short file names, such as MS-DOS. ----hheellpp ----ttaarrggeett--hheellpp Print text describing all the command line options instead of preprocessing anything. --vv Verbose mode. Print out GNU CPP's version number at the beginning of execution, and report the final form of the include path. --HH Print the name of each header file used, in addition to other normal activities. Each name is indented to show how deep in the ##iinncclluuddee stack it is. Precompiled header files are also printed, even if they are found to be invalid; an invalid precompiled header file is printed with ......xx and a valid one with ......!! . --vveerrssiioonn ----vveerrssiioonn Print out GNU CPP's version number. With one dash, proceed to preprocess as normal. With two dashes, exit immediately. EENNVVIIRROONNMMEENNTT This section describes the environment variables that affect how CPP operates. You can use them to specify directories or prefixes to use when searching for include files, or to control dependency output. Note that you can also specify places to search using options such as --II, and control dependency output with options like --MM. These take precedence over environment variables, which in turn take precedence over the configuration of GCC. CCPPAATTHH CC__IINNCCLLUUDDEE__PPAATTHH CCPPLLUUSS__IINNCCLLUUDDEE__PPAATTHH OOBBJJCC__IINNCCLLUUDDEE__PPAATTHH Each variable's value is a list of directories separated by a special character, much like PPAATTHH, in which to look for header files. The special character, "PATH_SEPARATOR", is target- dependent and determined at GCC build time. For Microsoft Windows- based targets it is a semicolon, and for almost all other targets it is a colon. CCPPAATTHH specifies a list of directories to be searched as if specified with --II, but after any paths given with --II options on the command line. This environment variable is used regardless of which language is being preprocessed. The remaining environment variables apply only when preprocessing the particular language indicated. Each specifies a list of directories to be searched as if specified with --iissyysstteemm, but after any paths given with --iissyysstteemm options on the command line. In all these variables, an empty element instructs the compiler to search its current working directory. Empty elements can appear at the beginning or end of a path. For instance, if the value of CCPPAATTHH is ":/special/include", that has the same effect as --II.. --II//ssppeecciiaall//iinncclluuddee. DDEEPPEENNDDEENNCCIIEESS__OOUUTTPPUUTT If this variable is set, its value specifies how to output dependencies for Make based on the non-system header files processed by the compiler. System header files are ignored in the dependency output. The value of DDEEPPEENNDDEENNCCIIEESS__OOUUTTPPUUTT can be just a file name, in which case the Make rules are written to that file, guessing the target name from the source file name. Or the value can have the form _f_i_l_e _t_a_r_g_e_t, in which case the rules are written to file _f_i_l_e using _t_a_r_g_e_t as the target name. In other words, this environment variable is equivalent to combining the options --MMMM and --MMFF, with an optional --MMTT switch too. SSUUNNPPRROO__DDEEPPEENNDDEENNCCIIEESS This variable is the same as DDEEPPEENNDDEENNCCIIEESS__OOUUTTPPUUTT (see above), except that system header files are not ignored, so it implies --MM rather than --MMMM. However, the dependence on the main input file is omitted. SSEEEE AALLSSOO _g_p_l(7), _g_f_d_l(7), _f_s_f_-_f_u_n_d_i_n_g(7), _g_c_c(1), _a_s(1), _l_d(1), and the Info entries for _c_p_p, _g_c_c, and _b_i_n_u_t_i_l_s. CCOOPPYYRRIIGGHHTT Copyright (c) 1987-2015 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation. A copy of the license is included in the man page _g_f_d_l(7). This manual contains no Invariant Sections. The Front-Cover Texts are (a) (see below), and the Back-Cover Texts are (b) (see below). (a) The FSF's Front-Cover Text is: A GNU Manual (b) The FSF's Back-Cover Text is: You have freedom to copy and modify this GNU Manual, like GNU software. Copies published by the Free Software Foundation raise funds for GNU development. gcc-4.9.4 2016-07-26 CPP(1)