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Thu Dec 19 23:28:33 1996 Ulrich Drepper <drepper@cygnus.com> * resolv/resolv.h: Update from BIND 4.9.5-P1. * resolv/res_comp.c: Likewise. * resolv/res_debug.c: Likewise. * resolv/Banner: Update version number. Thu Dec 19 20:58:53 1996 Ulrich Drepper <drepper@cygnus.com> * elf/dlfcn.h: Add extern "C" wrapper. * io/utime.h: Don't define NULL since this isn't allowed in POSIX. * io/sys/stat.h: Declare `lstat' only if __USE_BSD || __USE_XOPEN_EXTENDED. * locale/locale.h: Define NULL. * math/math.c: Don't include <errno.h> to define math errors. * stdlib/stdlib.h: Likewise. * posix/unistd.h: Don't declare environ. * posix/sys/utsname.h (struct utsname): Declare member domainname as __domainname is !__USE_GNU. * signal/signal.h: Declare size_t only if __USE_BSD || __USE_XOPEN_EXTENDED. * stdio/stdio.h: Don't declare cuserid when __USE_POSIX, but instead when __USE_XOPEN. * string/string.h: Define strndup only if __USE_GNU. * sysdeps/unix/sysv/linux/clock.c: New file. * sysdeps/unix/sysv/linux/timebits.h: Define CLOCKS_PER_SEC as 1000000 per X/Open standard. * features.h: Add code to recognize _POSIX_C_SOURCE value 199309. Define __USE_POSIX199309. * posix/unistd.h: Declare fdatasync only if __USE_POSIX199309. * time/time.c: Declare nanosleep only if __USE_POSIX199309. Patches by Rüdiger Helsch <rh@unifix.de>. * locale/locale.h: Add declaration of newlocale and freelocale. * new-malloc/Makefile (distibute): Add mtrace.awk. (dist-routines): Add mcheck and mtrace. (install-lib, non-lib.a): Define as libmcheck.a. * new-malloc/malloc.h: Add declaration of __malloc_initialized. * new-malloc/mcheck.c: New file. * new-malloc/mcheck.h: New file. * new-malloc/mtrace.c: New file. * new-malloc/mtrace.awk: New file. * posix/unistd.h: Correct prototype for usleep. * sysdeps/unix/bsd/usleep.c: De-ANSI-declfy. Correct return type. * sysdeps/unix/sysv/linux/usleep.c: Real implementation based on nanosleep. * signal/signal.h: Change protoype of __sigpause to take two arguments. Remove prototype for sigpause. Add two different macros named sigpause selected when __USE_BSD or __USE_XOPEN are defined. This is necessary since the old BSD definition of theis function collides with the X/Open definition. * sysdeps/posix/sigpause.c: Change function definition to also fit X/Open definition. * sysdeps/libm-i387/e_exp.S: Make sure stack is empty when the function is left. * sysdeps/libm-i387/e_expl.S: Likewise. Patch by HJ Lu. 1996-12-17 Paul Eggert <eggert@twinsun.com> * many, many files: Spelling corrections. * catgets/catgetsinfo.h (mmapped): Renamed from mmaped (in struct catalog_info.status). * mach/err_kern.sub (err_codes_unix), string/stratcliff.c (main): Fix spelling in message. * po/libc.pot: Fix spelling in message for `zic'; this anticipates a fix in the tzcode distribution. Wed Dec 18 15:48:02 1996 Ulrich Drepper <drepper@cygnus.com> * time/strftime.c: Implement ^ flag to cause output be converted to use upper case characters. * time/zic.c: Update from ADO tzcode1996n. Wed Dec 18 14:29:24 1996 Erik Naggum <erik@naggum.no> * time/strftime.c (add): Don't change global `i' until all is over. Define NULL is not already defined. Tue Dec 17 09:49:03 1996 Andreas Schwab <schwab@issan.informatik.uni-dortmund.de> * libio/iovsprintf.c (_IO_vsprintf): Change `&sf' to `&sf._sbf._f' to avoid the need for a cast. * libio/iovsscanf.c (_IO_vsscanf): Likewise. * sunrpc/rpc/xdr.h: Add prototype for xdr_free.
147 lines
6.0 KiB
Plaintext
147 lines
6.0 KiB
Plaintext
@node Feature Test Macros
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@subsection Feature Test Macros
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@cindex feature test macros
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The exact set of features available when you compile a source file
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is controlled by which @dfn{feature test macros} you define.
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If you compile your programs using @samp{gcc -ansi}, you get only the
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@w{ISO C} library features, unless you explicitly request additional
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features by defining one or more of the feature macros.
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@xref{Invoking GCC,, GNU CC Command Options, gcc.info, The GNU CC Manual},
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for more information about GCC options.@refill
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You should define these macros by using @samp{#define} preprocessor
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directives at the top of your source code files. These directives
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@emph{must} come before any @code{#include} of a system header file. It
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is best to make them the very first thing in the file, preceded only by
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comments. You could also use the @samp{-D} option to GCC, but it's
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better if you make the source files indicate their own meaning in a
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self-contained way.
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@comment (none)
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@comment POSIX.1
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@defvr Macro _POSIX_SOURCE
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If you define this macro, then the functionality from the POSIX.1
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standard (IEEE Standard 1003.1) is available, as well as all of the
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@w{ISO C} facilities.
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@end defvr
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@comment (none)
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@comment POSIX.2
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@defvr Macro _POSIX_C_SOURCE
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If you define this macro with a value of @code{1}, then the
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functionality from the POSIX.1 standard (IEEE Standard 1003.1) is made
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available. If you define this macro with a value of @code{2}, then both
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the functionality from the POSIX.1 standard and the functionality from
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the POSIX.2 standard (IEEE Standard 1003.2) are made available. This is
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in addition to the @w{ISO C} facilities.
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@end defvr
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@comment (none)
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@comment GNU
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@defvr Macro _BSD_SOURCE
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If you define this macro, functionality derived from 4.3 BSD Unix is
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included as well as the @w{ISO C}, POSIX.1, and POSIX.2 material.
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Some of the features derived from 4.3 BSD Unix conflict with the
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corresponding features specified by the POSIX.1 standard. If this
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macro is defined, the 4.3 BSD definitions take precedence over the
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POSIX definitions.
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Due to the nature of some of the conflicts between 4.3 BSD and POSIX.1,
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you need to use a special @dfn{BSD compatibility library} when linking
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programs compiled for BSD compatibility. This is because some functions
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must be defined in two different ways, one of them in the normal C
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library, and one of them in the compatibility library. If your program
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defines @code{_BSD_SOURCE}, you must give the option @samp{-lbsd-compat}
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to the compiler or linker when linking the program, to tell it to find
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functions in this special compatibility library before looking for them in
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the normal C library.
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@pindex -lbsd-compat
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@pindex bsd-compat
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@cindex BSD compatibility library.
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@end defvr
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@comment (none)
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@comment GNU
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@defvr Macro _SVID_SOURCE
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If you define this macro, functionality derived from SVID is
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included as well as the @w{ISO C}, POSIX.1, POSIX.2, and X/Open material.
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@end defvr
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@comment (none)
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@comment XOPEN
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@defvr Macro _XOPEN_SOURCE
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If you define this macro, functionality described in the X/Open
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Portability Guide is included. This is a superset of the POSIX.1 and
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POSIX.2 functionality and in fact @code{_POSIX_SOURCE} and
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@code{_POSIX_C_SOURCE} are automatically defined.
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As the unification of all Unices, functionality only available in
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BSD and SVID is also included.
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If the macro @code{_XOPEN_SOURCE_EXTENDED} is also defined, even more
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functionality is available. The extra functions will make all functions
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available which are necessary for the X/Open Unix brand.
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@end defvr
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@comment (none)
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@comment GNU
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@defvr Macro _GNU_SOURCE
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If you define this macro, everything is included: @w{ISO C}, POSIX.1,
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POSIX.2, BSD, SVID, X/Open, and GNU extensions. In the cases where
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POSIX.1 conflicts with BSD, the POSIX definitions take precedence.
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If you want to get the full effect of @code{_GNU_SOURCE} but make the
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BSD definitions take precedence over the POSIX definitions, use this
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sequence of definitions:
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@smallexample
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#define _GNU_SOURCE
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#define _BSD_SOURCE
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#define _SVID_SOURCE
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@end smallexample
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Note that if you do this, you must link your program with the BSD
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compatibility library by passing the @samp{-lbsd-compat} option to the
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compiler or linker. @strong{Note:} If you forget to do this, you may
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get very strange errors at run time.
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@end defvr
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@comment (none)
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@comment GNU
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@defvr Macro _REENTRANT
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@defvrx Macro _THREAD_SAFE
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If you define one of these macros, reentrant versions of several functions get
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declared. Some of the functions are specified in POSIX.1c but many others
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are only available on a few other systems or are unique to GNU libc.
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The problem is that the standardization of the thread safe C library
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interface still is behind.
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Unlike on some other systems no special version of the C library must be
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used for linking. There is only one version but while compiling this
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it must have been specified to compile as thread safe.
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@end defvr
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We recommend you use @code{_GNU_SOURCE} in new programs. If you don't
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specify the @samp{-ansi} option to GCC and don't define any of these
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macros explicitly, the effect is the same as defining
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@code{_POSIX_C_SOURCE} to 2 and @code{_POSIX_SOURCE},
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@code{_SVID_SOURCE}, and @code{_BSD_SOURCE} to 1.
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When you define a feature test macro to request a larger class of features,
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it is harmless to define in addition a feature test macro for a subset of
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those features. For example, if you define @code{_POSIX_C_SOURCE}, then
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defining @code{_POSIX_SOURCE} as well has no effect. Likewise, if you
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define @code{_GNU_SOURCE}, then defining either @code{_POSIX_SOURCE} or
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@code{_POSIX_C_SOURCE} or @code{_SVID_SOURCE} as well has no effect.
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Note, however, that the features of @code{_BSD_SOURCE} are not a subset of
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any of the other feature test macros supported. This is because it defines
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BSD features that take precedence over the POSIX features that are
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requested by the other macros. For this reason, defining
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@code{_BSD_SOURCE} in addition to the other feature test macros does have
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an effect: it causes the BSD features to take priority over the conflicting
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POSIX features.
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