dnl CF_XOPEN_SOURCE version: 66 updated: 2023/04/03 04:19:37
dnl ---------------
dnl Try to get _XOPEN_SOURCE defined properly that we can use POSIX functions,
dnl or adapt to the vendor's definitions to get equivalent functionality,
dnl without losing the common non-POSIX features.
dnl
dnl Parameters:
dnl	$1 is the nominal value for _XOPEN_SOURCE
dnl	$2 is the nominal value for _POSIX_C_SOURCE
dnl
dnl The default case prefers _XOPEN_SOURCE over _POSIX_C_SOURCE if the
dnl implementation predefines it, because X/Open and most implementations agree
dnl that the latter is a legacy or "aligned" value.
dnl
dnl Because _XOPEN_SOURCE is preferred, if defining _POSIX_C_SOURCE turns
dnl that off, then refrain from setting _POSIX_C_SOURCE explicitly.
dnl
dnl References:
dnl https://pubs.opengroup.org/onlinepubs/007904975/functions/xsh_chap02_02.html
dnl https://docs.oracle.com/cd/E19253-01/816-5175/standards-5/index.html
dnl https://www.gnu.org/software/libc/manual/html_node/Feature-Test-Macros.html
AC_DEFUN([CF_XOPEN_SOURCE],[
AC_REQUIRE([AC_CANONICAL_HOST])
AC_REQUIRE([CF_POSIX_VISIBLE])

if test "$cf_cv_posix_visible" = no; then

cf_XOPEN_SOURCE=ifelse([$1],,500,[$1])
cf_POSIX_C_SOURCE=ifelse([$2],,199506L,[$2])
cf_xopen_source=

case "$host_os" in
(aix[[4-7]]*)
	cf_xopen_source="-D_ALL_SOURCE"
	;;
(darwin[[0-8]].*)
	cf_xopen_source="-D_APPLE_C_SOURCE"
	;;
(darwin*)
	cf_xopen_source="-D_DARWIN_C_SOURCE"
	cf_XOPEN_SOURCE=
	;;
(freebsd*|dragonfly*|midnightbsd*)
	# 5.x headers associate
	#	_XOPEN_SOURCE=600 with _POSIX_C_SOURCE=200112L
	#	_XOPEN_SOURCE=500 with _POSIX_C_SOURCE=199506L
	cf_POSIX_C_SOURCE=200112L
	cf_XOPEN_SOURCE=600
	cf_xopen_source="-D_BSD_TYPES -D__BSD_VISIBLE -D_POSIX_C_SOURCE=$cf_POSIX_C_SOURCE -D_XOPEN_SOURCE=$cf_XOPEN_SOURCE"
	;;
(hpux11*)
	cf_xopen_source="-D_HPUX_SOURCE -D_XOPEN_SOURCE=500"
	;;
(hpux*)
	cf_xopen_source="-D_HPUX_SOURCE"
	;;
(irix[[56]].*)
	cf_xopen_source="-D_SGI_SOURCE"
	cf_XOPEN_SOURCE=
	;;
(linux*gnu|linux*gnuabi64|linux*gnuabin32|linux*gnueabi|linux*gnueabihf|linux*gnux32|uclinux*|gnu*|mint*|k*bsd*-gnu|cygwin|msys|mingw*)
	CF_GNU_SOURCE($cf_XOPEN_SOURCE)
	;;
(minix*)
	cf_xopen_source="-D_NETBSD_SOURCE" # POSIX.1-2001 features are ifdef'd with this...
	;;
(mirbsd*)
	# setting _XOPEN_SOURCE or _POSIX_SOURCE breaks <sys/select.h> and other headers which use u_int / u_short types
	cf_XOPEN_SOURCE=
	CF_POSIX_C_SOURCE($cf_POSIX_C_SOURCE)
	;;
(netbsd*)
	cf_xopen_source="-D_NETBSD_SOURCE" # setting _XOPEN_SOURCE breaks IPv6 for lynx on NetBSD 1.6, breaks xterm, is not needed for ncursesw
	;;
(openbsd[[6-9]]*)
	# OpenBSD 6.x has broken locale support, both compile-time and runtime.
	# see https://www.mail-archive.com/bugs@openbsd.org/msg13200.html
	# Abusing the conformance level is a workaround.
	AC_MSG_WARN(this system does not provide usable locale support)
	cf_xopen_source="-D_BSD_SOURCE"
	cf_XOPEN_SOURCE=700
	;;
(openbsd[[4-5]]*)
	# setting _XOPEN_SOURCE lower than 500 breaks g++ compile with wchar.h, needed for ncursesw
	cf_xopen_source="-D_BSD_SOURCE"
	cf_XOPEN_SOURCE=600
	;;
(openbsd*)
	# setting _XOPEN_SOURCE breaks xterm on OpenBSD 2.8, is not needed for ncursesw
	;;
(osf[[45]]*)
	cf_xopen_source="-D_OSF_SOURCE"
	;;
(nto-qnx*)
	cf_xopen_source="-D_QNX_SOURCE"
	;;
(sco*)
	# setting _XOPEN_SOURCE breaks Lynx on SCO Unix / OpenServer
	;;
(solaris2.*)
	cf_xopen_source="-D__EXTENSIONS__"
	cf_cv_xopen_source=broken
	;;
(sysv4.2uw2.*) # Novell/SCO UnixWare 2.x (tested on 2.1.2)
	cf_XOPEN_SOURCE=
	cf_POSIX_C_SOURCE=
	;;
(*)
	CF_TRY_XOPEN_SOURCE
	cf_save_xopen_cppflags="$CPPFLAGS"
	CF_POSIX_C_SOURCE($cf_POSIX_C_SOURCE)
	# Some of these niche implementations use copy/paste, double-check...
	if test "$cf_cv_xopen_source" = no ; then
		CF_VERBOSE(checking if _POSIX_C_SOURCE interferes with _XOPEN_SOURCE)
		AC_TRY_COMPILE(CF__XOPEN_SOURCE_HEAD,CF__XOPEN_SOURCE_BODY,,[
			AC_MSG_WARN(_POSIX_C_SOURCE definition is not usable)
			CPPFLAGS="$cf_save_xopen_cppflags"])
	fi
	;;
esac

if test -n "$cf_xopen_source" ; then
	CF_APPEND_CFLAGS($cf_xopen_source,true)
fi

dnl In anything but the default case, we may have system-specific setting
dnl which is still not guaranteed to provide all of the entrypoints that
dnl _XOPEN_SOURCE would yield.
if test -n "$cf_XOPEN_SOURCE" && test -z "$cf_cv_xopen_source" ; then
	AC_MSG_CHECKING(if _XOPEN_SOURCE really is set)
	AC_TRY_COMPILE([#include <stdlib.h>],[
#ifndef _XOPEN_SOURCE
#error _XOPEN_SOURCE is not defined
#endif],
	[cf_XOPEN_SOURCE_set=yes],
	[cf_XOPEN_SOURCE_set=no])
	AC_MSG_RESULT($cf_XOPEN_SOURCE_set)
	if test "$cf_XOPEN_SOURCE_set" = yes
	then
		AC_TRY_COMPILE([#include <stdlib.h>],[
#if (_XOPEN_SOURCE - 0) < $cf_XOPEN_SOURCE
#error (_XOPEN_SOURCE - 0) < $cf_XOPEN_SOURCE
#endif],
		[cf_XOPEN_SOURCE_set_ok=yes],
		[cf_XOPEN_SOURCE_set_ok=no])
		if test "$cf_XOPEN_SOURCE_set_ok" = no
		then
			AC_MSG_WARN(_XOPEN_SOURCE is lower than requested)
		fi
	else
		CF_TRY_XOPEN_SOURCE
	fi
fi
fi # cf_cv_posix_visible
])
