cpp(1) GNU Tools cpp(1) NAME cccp, cpp - The GNU C-Compatible Compiler Preprocessor. SYNOPSIS cccp [-$] [-C] [-D_n_a_m_e[=_d_e_f_i_n_i_t_i_o_n]] [-dD] [-dM] [-I _d_i_r_e_c_t_o_r_y] [-H] [-I-] [-imacros _f_i_l_e] [-include _f_i_l_e] [-lang-c] [-lang-c++] [-lang-objc] [-lang-objc++] [-lint] [-M] [-MD] [-MM] [-MMD] [-nostdinc] [-P] [-pedantic] [-pedantic-errors] [-trigraphs] [-U_n_a_m_e] [-undef] [-Wtrigraphs] [-Wcomment] [-Wall] [-Wtraditional] [_i_n_f_i_l_e|-] [_o_u_t_f_i_l_e|-] DESCRIPTION The C preprocessor is a _m_a_c_r_o _p_r_o_c_e_s_s_o_r that is used au- tomatically by the C compiler to transform your program be- fore actual compilation. It is called a macro processor be- cause it allows you to define _m_a_c_r_o_s, which are brief abbre- viations for longer constructs. The C preprocessor provides four separate facilities that you can use as you see fit: o+ Inclusion of header files. These are files of declara- tions that can be substituted into your program. o+ Macro expansion. You can define _m_a_c_r_o_s, which are ab- breviations for arbitrary fragments of C code, and then the C preprocessor will replace the macros with their definitions throughout the program. o+ Conditional compilation. Using special preprocessor commands, you can include or exclude parts of the pro- gram according to various conditions. o+ Line control. If you use a program to combine or rear- range source files into an intermediate file which is then compiled, you can use line control to inform the compiler of where each source line originally came from. C preprocessors vary in some details. For a full explana- tion of the GNU C preprocessor, see the info file `cpp.info', or the manual _T_h_e _C _P_r_e_p_r_o_c_e_s_s_o_r. Both of these are built from the same documentation source file, `cpp.texinfo'. The GNU C preprocessor provides a superset of the features of ANSI Standard C. ANSI Standard C requires the rejection of many harmless con- structs commonly used by today's C programs. Such incompa- tibility would be inconvenient for users, so the GNU C preprocessor is configured to accept these constructs by de- GNU Tools Last change: 2Jan1992 1 cpp(1) GNU Tools cpp(1) fault. Strictly speaking, to get ANSI Standard C, you must use the options `-trigraphs', `-undef' and `-pedantic', but in practice the consequences of having strict ANSI Standard C make it undesirable to do this. Most often when you use the C preprocessor you will not have to invoke it explicitly: the C compiler will do so automati- cally. However, the preprocessor is sometimes useful indi- vidually. When you call the preprocessor individually, either name (cpp or cccp) will do-they are completely synonymous. 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 `#include'. 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 _o_u_t_f_i_l_e or both file names are omitted, the standard output and standard input are used for the omitted file names. OPTIONS Here is a table of command options accepted by the C prepro- cessor. These options can also be given when compiling a C program; they are passed along automatically to the prepro- cessor when it is invoked by the compiler. -P Inhibit generation of `#'-lines with line-number infor- mation 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 `#'-lines. -C Do not discard comments: pass them through to the out- put file. Comments appearing in arguments of a macro call will be copied to the output before the expansion of the macro call. -trigraphs Process ANSI standard trigraph sequences. These are three-character sequences, all starting with `??', that are defined by ANSI C to stand for single characters. For example, `??/' stands for `\', so `'??/n'' is a character constant for a newline. Strictly speaking, the GNU C preprocessor does not support all programs in ANSI Standard C unless `-trigraphs' is used, but if you ever notice the difference it will be with relief. GNU Tools Last change: 2Jan1992 2 cpp(1) GNU Tools cpp(1) You don't want to know any more about trigraphs. -pedantic Issue warnings required by the ANSI C standard in cer- tain cases such as when text other than a comment fol- lows `#else' or `#endif'. -pedantic-errors Like `-pedantic', except that errors are produced rath- er than warnings. -Wtrigraphs Warn if any trigraphs are encountered (assuming they are enabled). -Wcomment -Wcomments Warn whenever a comment-start sequence `/*' appears in a comment. (Both forms have the same effect). -Wall Requests both `-Wtrigraphs' and `-Wcomment' (but not `-Wtraditional'). -Wtraditional Warn about certain constructs that behave differently in traditional and ANSI C. -I _d_i_r_e_c_t_o_r_y Add the directory _d_i_r_e_c_t_o_r_y to the end of the list of directories to be searched for header files. This can be used to override a system header file, substituting your own version, since these directories are searched before the system header file directories. If you use more than one `-I' option, the directories are scanned in left-to-right order; the standard system directories come after. -I- Any directories specified with `-I' options before the `-I-' option are searched only for the case of `#in- clude _f_i_l_e"'; they are not searched for `#include <_f_i_l_e>'. If additional directories are specified with `-I' op- tions after the `-I-', these directories are searched for all `#include' directives. In addition, the `-I-' option inhibits the use of the current directory as the first search directory for `#include _f_i_l_e"'. Therefore, the current directory is searched only if it is requested explicitly with `-I.'. GNU Tools Last change: 2Jan1992 3 cpp(1) GNU Tools cpp(1) Specifying both `-I-' and `-I.' allows you to control precisely which directories are searched before the current one and which are searched after. -nostdinc Do not search the standard system directories for header files. Only the directories you have specified with `-I' options (and the current directory, if ap- propriate) are searched. -D _n_a_m_e Predefine _n_a_m_e as a macro, with definition `1'. -D _n_a_m_e=_d_e_f_i_n_i_t_i_o_n Predefine _n_a_m_e as a macro, with definition _d_e_f_i_n_i_t_i_o_n. There are no restrictions on the contents of _d_e_f_i_n_i_- _t_i_o_n, but 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 use more than one `-D' for the same _n_a_m_e, the rightmost definition takes effect. -U _n_a_m_e Do not predefine _n_a_m_e. If both `-U' and `-D' are specified for one name, the `-U' beats the `-D' and the name is not predefined. -undef Do not predefine any nonstandard macros. -dM Instead of outputting the result of preprocessing, out- put a list of `#define' commands for all the macros de- fined during the execution of the preprocessor, includ- ing predefined macros. This gives you a way of finding out what is predefined in your version of the prepro- cessor; assuming you have no file `foo.h', the command touch foo.h; cpp -dM foo.h will show the values of any predefined macros. -dD Like `-dM' except in two respects: it does _n_o_t include the predefined macros, and it outputs _b_o_t_h the `#de- fine' commands and the result of preprocessing. Both kinds of output go to the standard output file. -M Instead of outputting the result of preprocessing, out- put a rule suitable for make describing the dependen- cies of the main source file. The preprocessor outputs one make rule containing the object file name for that source file, a colon, and the names of all the included GNU Tools Last change: 2Jan1992 4 cpp(1) GNU Tools cpp(1) files. If there are many included files then the rule is split into several lines using `'-newline. This feature is used in automatic updating of makefiles. -MM Like `-M' but mention only the files included with `#include "_f_i_l_e"'. System header files included with `#include <_f_i_l_e>' are omitted. -MD Like `-M' but the dependency information is written to files with names made by replacing `.c' with `.d' at the end of the input file names. This is in addition to compiling the file as specified-`-MD' does not inhi- bit ordinary compilation the way `-M' does. In Mach, you can use the utility md to merge the `.d' files into a single dependency file suitable for using with the `make' command. -MMD Like `-MD' except mention only user header files, not system header files. -H Print the name of each header file used, in addition to other normal activities. -imacros _f_i_l_e Process _f_i_l_e as input, discarding the resulting out- put, before processing the regular input file. Because the output generated from _f_i_l_e is discarded, the only effect of `-imacros _f_i_l_e' is to make the macros defined in _f_i_l_e available for use in the main input. The preprocessor evaluates any `-D' and `-U' options on the command line before processing `-imacros _f_i_l_e' . -include _f_i_l_e Process _f_i_l_e as input, and include all the resulting output, before processing the regular input file. -lang-c -lang-c++ -lang-objc -lang-objc++ Specify the source language. `-lang-c++' makes the preprocessor handle C++ comment syntax, and includes extra default include directories for C++, and `-lang- objc' enables the Objective C `#import' directive. `-lang-c' explicitly turns off both of these exten- sions, and `-lang-objc++' enables both. GNU Tools Last change: 2Jan1992 5 cpp(1) GNU Tools cpp(1) These options are generated by the compiler driver gcc, but not passed from the `gcc' command line. -lint Look for commands to the program checker lint embedded in comments, and emit them preceded by `#pragma lint'. For example, the comment `/* NOTREACHED */' becomes `#pragma lint NOTREACHED'. This option is available only when you call cpp direct- ly; gcc will not pass it from its command line. -$ Forbid the use of `$' in identifiers. This is required for ANSI conformance. gcc automatically supplies this option to the preprocessor if you specify `-ansi', but gcc doesn't recognize the `-$' option itself-to use it without the other effects of `-ansi', you must call the preprocessor directly. SEE ALSO `Cpp' entry in info; _T_h_e _C _P_r_e_p_r_o_c_e_s_s_o_r, Richard M. Stall- man. gcc(1); `Gcc' entry in info; _U_s_i_n_g _a_n_d _P_o_r_t_i_n_g _G_N_U _C_C (_f_o_r _v_e_r_s_i_o_n _2._0), Richard M. Stallman. COPYING Copyright (c) 1991, 1992 Free Software Foundation, Inc. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this per- mission notice are preserved on all copies. Permission is granted to copy and distribute modified ver- sions of this manual under the conditions for verbatim copy- ing, provided that the entire resulting derived work is dis- tributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above condi- tions for modified versions, except that this permission no- tice may be included in translations approved by the Free Software Foundation instead of in the original English. GNU Tools Last change: 2Jan1992 6