On 09/07/2011 10:33 PM, Bruno Haible wrote:
The crypt example is particularly annoying, as without _XOPEN_SOURCE
defined it's not defined, even though POSIX_VERSION is>= 200112L, and
it's in that version of POSIX (of course, that's a glibc bug
Setting _POSIX_C_SOURCE to 200809L _should_ automatically turn on _XOPEN_SOURCE
of 700. (Setting it to 200112L sets _XOPEN_SOURCE to 600, but POSIX 2001 is 10
years old, and you're better off catering to POSIX 2008 these days).
$ cat foo.c
#define _POSIX_C_SOURCE 200112L
#include<unistd.h>
$ gcc -E foo.c | grep crypt
Glibc bug. XSI shading means that a non-XSI implementation need not have crypt by
default, but glibc is an XSI implementation, so requesting compliance with POSIX 2008
means that crypt() should be visible in <unistd.h>. There's no feature macro
needed to turn on XSI functions - either you have an XSI system and they are all
available by default, or you do not have an XSI system (usually embedded systems) and
the system documents that it is not provide XSI.