dnl CF_POSIX_VISIBLE version: 1 updated: 2018/12/31 20:46:17
dnl ----------------
dnl POSIX documents test-macros which an application may set before any system
dnl headers are included to make features available.
dnl
dnl Some BSD platforms (originally FreeBSD, but copied by a few others)
dnl diverged from POSIX in 2002 by setting symbols which make all of the most
dnl recent features visible in the system header files unless the application
dnl overrides the corresponding test-macros.  Doing that introduces portability
dnl problems.
dnl
dnl This macro makes a special check for the symbols used for this, to avoid a
dnl conflicting definition.
AC_DEFUN([CF_POSIX_VISIBLE],
[
AC_CACHE_CHECK(if the POSIX test-macros are already defined,cf_cv_posix_visible,[
AC_TRY_COMPILE([#include <stdio.h>],[
#if defined(__POSIX_VISIBLE) && ((__POSIX_VISIBLE - 0L) > 0) \
	&& defined(__XSI_VISIBLE) && ((__XSI_VISIBLE - 0L) > 0) \
	&& defined(__BSD_VISIBLE) && ((__BSD_VISIBLE - 0L) > 0) \
	&& defined(__ISO_C_VISIBLE) && ((__ISO_C_VISIBLE - 0L) > 0)
#error conflicting symbols found
#endif
],[cf_cv_posix_visible=no],[cf_cv_posix_visible=yes])
])
])dnl
