diff options
author | Roland McGrath <roland@gnu.org> | 1994-10-25 22:48:59 +0000 |
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committer | Roland McGrath <roland@gnu.org> | 1994-10-25 22:48:59 +0000 |
commit | abb3474673aa702192aa609554b70de6f92125f1 (patch) | |
tree | 4533aa61a4e5292d8520da1e874c0ee453a95c65 | |
parent | dc750d19339273490eecb021a208dd11edd3e99f (diff) |
(Feature Test Macros): Node moved off to creature.texi.
-rw-r--r-- | manual/intro.texi | 117 |
1 files changed, 3 insertions, 114 deletions
diff --git a/manual/intro.texi b/manual/intro.texi index e698272d7c..9ca2ade9f8 100644 --- a/manual/intro.texi +++ b/manual/intro.texi @@ -515,120 +515,9 @@ The header file @file{termios.h} reserves names prefixed with @samp{c_}, @pindex termios.h @end itemize - -@node Feature Test Macros, , Reserved Names, Using the Library -@subsection Feature Test Macros - -@cindex feature test macros -The exact set of features available when you compile a source file -is controlled by which @dfn{feature test macros} you define. - -If you compile your programs using @samp{gcc -ansi}, you get only the -ANSI C library features, unless you explicitly request additional -features by defining one or more of the feature macros. -@xref{Invoking GCC,, GNU CC Command Options, gcc.info, The GNU CC Manual}, -for more information about GCC options.@refill - -You should define these macros by using @samp{#define} preprocessor -directives at the top of your source code files. These directives -@emph{must} come before any @code{#include} of a system header file. It -is best to make them the very first thing in the file, preceded only by -comments. You could also use the @samp{-D} option to GCC, but it's -better if you make the source files indicate their own meaning in a -self-contained way. - -@comment (none) -@comment POSIX.1 -@defvr Macro _POSIX_SOURCE -If you define this macro, then the functionality from the POSIX.1 -standard (IEEE Standard 1003.1) is available, as well as all of the -ANSI C facilities. -@end defvr - -@comment (none) -@comment POSIX.2 -@defvr Macro _POSIX_C_SOURCE -If you define this macro with a value of @code{1}, then the -functionality from the POSIX.1 standard (IEEE Standard 1003.1) is made -available. If you define this macro with a value of @code{2}, then both -the functionality from the POSIX.1 standard and the functionality from -the POSIX.2 standard (IEEE Standard 1003.2) are made available. This is -in addition to the ANSI C facilities. -@end defvr - -@comment (none) -@comment GNU -@defvr Macro _BSD_SOURCE -If you define this macro, functionality derived from 4.3 BSD Unix is -included as well as the ANSI C, POSIX.1, and POSIX.2 material. - -Some of the features derived from 4.3 BSD Unix conflict with the -corresponding features specified by the POSIX.1 standard. If this -macro is defined, the 4.3 BSD definitions take precedence over the -POSIX definitions. - -Due to the nature of some of the conflicts between 4.3 BSD and POSIX.1, -you need to use a special @dfn{BSD compatibility library} when linking -programs compiled for BSD compatibility. This is because some functions -must be defined in two different ways, one of them in the normal C -library, and one of them in the compatibility library. If your program -defines @code{_BSD_SOURCE}, you must give the option @samp{-lbsd-compat} -to the compiler or linker when linking the program, to tell it to find -functions in this special compatibility library before looking for them in -the normal C library. -@pindex -lbsd-compat -@pindex bsd-compat -@cindex BSD compatibility library. -@end defvr - -@comment (none) -@comment GNU -@defvr Macro _SVID_SOURCE -If you define this macro, functionality derived from SVID is -included as well as the ANSI C, POSIX.1, and POSIX.2 material. -@end defvr - -@comment (none) -@comment GNU -@defvr Macro _GNU_SOURCE -If you define this macro, everything is included: ANSI C, POSIX.1, -POSIX.2, BSD, SVID, and GNU extensions. In the cases where POSIX.1 -conflicts with BSD, the POSIX definitions take precedence. - -If you want to get the full effect of @code{_GNU_SOURCE} but make the -BSD definitions take precedence over the POSIX definitions, use this -sequence of definitions: - -@smallexample -#define _GNU_SOURCE -#define _BSD_SOURCE -#define _SVID_SOURCE -@end smallexample - -Note that if you do this, you must link your program with the BSD -compatibility library by passing the @samp{-lbsd-compat} option to the -compiler or linker. @strong{Note:} If you forget to do this, you may -get very strange errors at run time. -@end defvr - -We recommend you use @code{_GNU_SOURCE} in new programs. If you don't -specify the @samp{-ansi} option to GCC and don't define any of these macros -explicitly, the effect is the same as defining @code{_GNU_SOURCE}. - -When you define a feature test macro to request a larger class of features, -it is harmless to define in addition a feature test macro for a subset of -those features. For example, if you define @code{_POSIX_C_SOURCE}, then -defining @code{_POSIX_SOURCE} as well has no effect. Likewise, if you -define @code{_GNU_SOURCE}, then defining either @code{_POSIX_SOURCE} or -@code{_POSIX_C_SOURCE} or @code{_SVID_SOURCE} as well has no effect. - -Note, however, that the features of @code{_BSD_SOURCE} are not a subset of -any of the other feature test macros supported. This is because it defines -BSD features that take precedence over the POSIX features that are -requested by the other macros. For this reason, defining -@code{_BSD_SOURCE} in addition to the other feature test macros does have -an effect: it causes the BSD features to take priority over the conflicting -POSIX features. +@comment Include the section on Creature Nest Macros. +@comment It is in a separate file so it can be formatted into ../NOTES. +@include creature.texi @node Roadmap to the Manual, , Using the Library, Introduction @section Roadmap to the Manual |