This function is missing on all non-glibc platforms:
glibc 2.3.2, Mac OS X 10.5, FreeBSD 6.4, NetBSD 5.0, OpenBSD 3.8, Minix 3.1.8, AIX 7.1, HP-UX 11.31, IRIX 6.5, OSF/1 5.1, Solaris 11 2011-11, Cygwin, mingw, MSVC 9, Interix 3.5, BeOS.
This function has a different signature on some platforms:
glibc 2.3.3.