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+# serial 18 -*- Autoconf -*-
+# Enable extensions on systems that normally disable them.
+
+# Copyright (C) 2003, 2006-2019 Free Software Foundation, Inc.
+# This file is free software; the Free Software Foundation
+# gives unlimited permission to copy and/or distribute it,
+# with or without modifications, as long as this notice is preserved.
+
+# This definition of AC_USE_SYSTEM_EXTENSIONS is stolen from git
+# Autoconf. Perhaps we can remove this once we can assume Autoconf
+# 2.70 or later everywhere, but since Autoconf mutates rapidly
+# enough in this area it's likely we'll need to redefine
+# AC_USE_SYSTEM_EXTENSIONS for quite some time.
+
+# If autoconf reports a warning
+# warning: AC_COMPILE_IFELSE was called before AC_USE_SYSTEM_EXTENSIONS
+# or warning: AC_RUN_IFELSE was called before AC_USE_SYSTEM_EXTENSIONS
+# the fix is
+# 1) to ensure that AC_USE_SYSTEM_EXTENSIONS is never directly invoked
+# but always AC_REQUIREd,
+# 2) to ensure that for each occurrence of
+# AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+# or
+# AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+# the corresponding gnulib module description has 'extensions' among
+# its dependencies. This will ensure that the gl_USE_SYSTEM_EXTENSIONS
+# invocation occurs in gl_EARLY, not in gl_INIT.
+
+# AC_USE_SYSTEM_EXTENSIONS
+# ------------------------
+# Enable extensions on systems that normally disable them,
+# typically due to standards-conformance issues.
+#
+# Remember that #undef in AH_VERBATIM gets replaced with #define by
+# AC_DEFINE. The goal here is to define all known feature-enabling
+# macros, then, if reports of conflicts are made, disable macros that
+# cause problems on some platforms (such as __EXTENSIONS__).
+AC_DEFUN_ONCE([AC_USE_SYSTEM_EXTENSIONS],
+[AC_BEFORE([$0], [AC_COMPILE_IFELSE])dnl
+AC_BEFORE([$0], [AC_RUN_IFELSE])dnl
+
+ AC_CHECK_HEADER([minix/config.h], [MINIX=yes], [MINIX=])
+ if test "$MINIX" = yes; then
+ AC_DEFINE([_POSIX_SOURCE], [1],
+ [Define to 1 if you need to in order for 'stat' and other
+ things to work.])
+ AC_DEFINE([_POSIX_1_SOURCE], [2],
+ [Define to 2 if the system does not provide POSIX.1 features
+ except with this defined.])
+ AC_DEFINE([_MINIX], [1],
+ [Define to 1 if on MINIX.])
+ AC_DEFINE([_NETBSD_SOURCE], [1],
+ [Define to 1 to make NetBSD features available. MINIX 3 needs this.])
+ fi
+
+dnl Use a different key than __EXTENSIONS__, as that name broke existing
+dnl configure.ac when using autoheader 2.62.
+ AH_VERBATIM([USE_SYSTEM_EXTENSIONS],
+[/* Enable extensions on AIX 3, Interix. */
+#ifndef _ALL_SOURCE
+# undef _ALL_SOURCE
+#endif
+/* Enable general extensions on macOS. */
+#ifndef _DARWIN_C_SOURCE
+# undef _DARWIN_C_SOURCE
+#endif
+/* Enable GNU extensions on systems that have them. */
+#ifndef _GNU_SOURCE
+# undef _GNU_SOURCE
+#endif
+/* Enable NetBSD extensions on NetBSD. */
+#ifndef _NETBSD_SOURCE
+# undef _NETBSD_SOURCE
+#endif
+/* Enable OpenBSD extensions on NetBSD. */
+#ifndef _OPENBSD_SOURCE
+# undef _OPENBSD_SOURCE
+#endif
+/* Enable threading extensions on Solaris. */
+#ifndef _POSIX_PTHREAD_SEMANTICS
+# undef _POSIX_PTHREAD_SEMANTICS
+#endif
+/* Enable extensions specified by ISO/IEC TS 18661-5:2014. */
+#ifndef __STDC_WANT_IEC_60559_ATTRIBS_EXT__
+# undef __STDC_WANT_IEC_60559_ATTRIBS_EXT__
+#endif
+/* Enable extensions specified by ISO/IEC TS 18661-1:2014. */
+#ifndef __STDC_WANT_IEC_60559_BFP_EXT__
+# undef __STDC_WANT_IEC_60559_BFP_EXT__
+#endif
+/* Enable extensions specified by ISO/IEC TS 18661-2:2015. */
+#ifndef __STDC_WANT_IEC_60559_DFP_EXT__
+# undef __STDC_WANT_IEC_60559_DFP_EXT__
+#endif
+/* Enable extensions specified by ISO/IEC TS 18661-4:2015. */
+#ifndef __STDC_WANT_IEC_60559_FUNCS_EXT__
+# undef __STDC_WANT_IEC_60559_FUNCS_EXT__
+#endif
+/* Enable extensions specified by ISO/IEC TS 18661-3:2015. */
+#ifndef __STDC_WANT_IEC_60559_TYPES_EXT__
+# undef __STDC_WANT_IEC_60559_TYPES_EXT__
+#endif
+/* Enable extensions specified by ISO/IEC TR 24731-2:2010. */
+#ifndef __STDC_WANT_LIB_EXT2__
+# undef __STDC_WANT_LIB_EXT2__
+#endif
+/* Enable extensions specified by ISO/IEC 24747:2009. */
+#ifndef __STDC_WANT_MATH_SPEC_FUNCS__
+# undef __STDC_WANT_MATH_SPEC_FUNCS__
+#endif
+/* Enable extensions on HP NonStop. */
+#ifndef _TANDEM_SOURCE
+# undef _TANDEM_SOURCE
+#endif
+/* Enable X/Open extensions if necessary. HP-UX 11.11 defines
+ mbstate_t only if _XOPEN_SOURCE is defined to 500, regardless of
+ whether compiling with -Ae or -D_HPUX_SOURCE=1. */
+#ifndef _XOPEN_SOURCE
+# undef _XOPEN_SOURCE
+#endif
+/* Enable X/Open compliant socket functions that do not require linking
+ with -lxnet on HP-UX 11.11. */
+#ifndef _HPUX_ALT_XOPEN_SOCKET_API
+# undef _HPUX_ALT_XOPEN_SOCKET_API
+#endif
+/* Enable general extensions on Solaris. */
+#ifndef __EXTENSIONS__
+# undef __EXTENSIONS__
+#endif
+])
+ AC_CACHE_CHECK([whether it is safe to define __EXTENSIONS__],
+ [ac_cv_safe_to_define___extensions__],
+ [AC_COMPILE_IFELSE(
+ [AC_LANG_PROGRAM([[
+# define __EXTENSIONS__ 1
+ ]AC_INCLUDES_DEFAULT])],
+ [ac_cv_safe_to_define___extensions__=yes],
+ [ac_cv_safe_to_define___extensions__=no])])
+ test $ac_cv_safe_to_define___extensions__ = yes &&
+ AC_DEFINE([__EXTENSIONS__])
+ AC_DEFINE([_ALL_SOURCE])
+ AC_DEFINE([_DARWIN_C_SOURCE])
+ AC_DEFINE([_GNU_SOURCE])
+ AC_DEFINE([_NETBSD_SOURCE])
+ AC_DEFINE([_OPENBSD_SOURCE])
+ AC_DEFINE([_POSIX_PTHREAD_SEMANTICS])
+ AC_DEFINE([__STDC_WANT_IEC_60559_ATTRIBS_EXT__])
+ AC_DEFINE([__STDC_WANT_IEC_60559_BFP_EXT__])
+ AC_DEFINE([__STDC_WANT_IEC_60559_DFP_EXT__])
+ AC_DEFINE([__STDC_WANT_IEC_60559_FUNCS_EXT__])
+ AC_DEFINE([__STDC_WANT_IEC_60559_TYPES_EXT__])
+ AC_DEFINE([__STDC_WANT_LIB_EXT2__])
+ AC_DEFINE([__STDC_WANT_MATH_SPEC_FUNCS__])
+ AC_DEFINE([_TANDEM_SOURCE])
+ AC_CACHE_CHECK([whether _XOPEN_SOURCE should be defined],
+ [ac_cv_should_define__xopen_source],
+ [ac_cv_should_define__xopen_source=no
+ AC_COMPILE_IFELSE(
+ [AC_LANG_PROGRAM([[
+ #include <wchar.h>
+ mbstate_t x;]])],
+ [],
+ [AC_COMPILE_IFELSE(
+ [AC_LANG_PROGRAM([[
+ #define _XOPEN_SOURCE 500
+ #include <wchar.h>
+ mbstate_t x;]])],
+ [ac_cv_should_define__xopen_source=yes])])])
+ test $ac_cv_should_define__xopen_source = yes &&
+ AC_DEFINE([_XOPEN_SOURCE], [500])
+ AC_DEFINE([_HPUX_ALT_XOPEN_SOCKET_API])
+])# AC_USE_SYSTEM_EXTENSIONS
+
+# gl_USE_SYSTEM_EXTENSIONS
+# ------------------------
+# Enable extensions on systems that normally disable them,
+# typically due to standards-conformance issues.
+AC_DEFUN_ONCE([gl_USE_SYSTEM_EXTENSIONS],
+[
+ dnl Require this macro before AC_USE_SYSTEM_EXTENSIONS.
+ dnl gnulib does not need it. But if it gets required by third-party macros
+ dnl after AC_USE_SYSTEM_EXTENSIONS is required, autoconf 2.62..2.63 emit a
+ dnl warning: "AC_COMPILE_IFELSE was called before AC_USE_SYSTEM_EXTENSIONS".
+ dnl Note: We can do this only for one of the macros AC_AIX, AC_GNU_SOURCE,
+ dnl AC_MINIX. If people still use AC_AIX or AC_MINIX, they are out of luck.
+ AC_REQUIRE([AC_GNU_SOURCE])
+
+ AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+])