5.12 Posix Variants

The following macro makes it possible to use features of Posix that are extensions to C, as well as platform extensions not defined by Posix.

Macro: AC_USE_SYSTEM_EXTENSIONS

This macro was introduced in Autoconf 2.60. If possible, enable extensions to C or Posix on hosts that normally disable the extensions, typically due to standards-conformance namespace issues. This should be called before any macros that run the C compiler. The following preprocessor macros are defined where appropriate:

_GNU_SOURCE

Enable extensions on GNU/Linux.

__EXTENSIONS__

Enable general extensions on Solaris.

_POSIX_PTHREAD_SEMANTICS

Enable threading extensions on Solaris.

_TANDEM_SOURCE

Enable extensions for the HP NonStop platform.

_ALL_SOURCE

Enable extensions for AIX 3, and for Interix.

_POSIX_SOURCE

Enable Posix functions for Minix.

_POSIX_1_SOURCE

Enable additional Posix functions for Minix.

_MINIX

Identify Minix platform. This particular preprocessor macro is obsolescent, and may be removed in a future release of Autoconf.