Add `extern "C"` to header
[argpar.git] / m4 / ac_extensions.m4
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a99ee691
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1# serial 13 -*- Autoconf -*-
2# Enable extensions on systems that normally disable them.
3
4# Copyright (C) 2003, 2006-2016 Free Software Foundation, Inc.
5# This file is free software; the Free Software Foundation
6# gives unlimited permission to copy and/or distribute it,
7# with or without modifications, as long as this notice is preserved.
8
9# This definition of AC_USE_SYSTEM_EXTENSIONS is stolen from git
10# Autoconf. Perhaps we can remove this once we can assume Autoconf
11# 2.70 or later everywhere, but since Autoconf mutates rapidly
12# enough in this area it's likely we'll need to redefine
13# AC_USE_SYSTEM_EXTENSIONS for quite some time.
14
15# If autoconf reports a warning
16# warning: AC_COMPILE_IFELSE was called before AC_USE_SYSTEM_EXTENSIONS
17# or warning: AC_RUN_IFELSE was called before AC_USE_SYSTEM_EXTENSIONS
18# the fix is
19# 1) to ensure that AC_USE_SYSTEM_EXTENSIONS is never directly invoked
20# but always AC_REQUIREd,
21# 2) to ensure that for each occurrence of
22# AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
23# or
24# AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
25# the corresponding gnulib module description has 'extensions' among
26# its dependencies. This will ensure that the gl_USE_SYSTEM_EXTENSIONS
27# invocation occurs in gl_EARLY, not in gl_INIT.
28
29# AC_USE_SYSTEM_EXTENSIONS
30# ------------------------
31# Enable extensions on systems that normally disable them,
32# typically due to standards-conformance issues.
33#
34# Remember that #undef in AH_VERBATIM gets replaced with #define by
35# AC_DEFINE. The goal here is to define all known feature-enabling
36# macros, then, if reports of conflicts are made, disable macros that
37# cause problems on some platforms (such as __EXTENSIONS__).
38AC_DEFUN_ONCE([AC_USE_SYSTEM_EXTENSIONS],
39[AC_BEFORE([$0], [AC_COMPILE_IFELSE])dnl
40AC_BEFORE([$0], [AC_RUN_IFELSE])dnl
41
42 AC_CHECK_HEADER([minix/config.h], [MINIX=yes], [MINIX=])
43 if test "$MINIX" = yes; then
44 AC_DEFINE([_POSIX_SOURCE], [1],
45 [Define to 1 if you need to in order for 'stat' and other
46 things to work.])
47 AC_DEFINE([_POSIX_1_SOURCE], [2],
48 [Define to 2 if the system does not provide POSIX.1 features
49 except with this defined.])
50 AC_DEFINE([_MINIX], [1],
51 [Define to 1 if on MINIX.])
52 AC_DEFINE([_NETBSD_SOURCE], [1],
53 [Define to 1 to make NetBSD features available. MINIX 3 needs this.])
54 fi
55
56dnl Use a different key than __EXTENSIONS__, as that name broke existing
57dnl configure.ac when using autoheader 2.62.
58 AH_VERBATIM([USE_SYSTEM_EXTENSIONS],
59[/* Enable extensions on AIX 3, Interix. */
60#ifndef _ALL_SOURCE
61# undef _ALL_SOURCE
62#endif
63/* Enable general extensions on OS X. */
64#ifndef _DARWIN_C_SOURCE
65# undef _DARWIN_C_SOURCE
66#endif
67/* Enable GNU extensions on systems that have them. */
68#ifndef _GNU_SOURCE
69# undef _GNU_SOURCE
70#endif
71/* Use GNU style printf and scanf. */
72#ifndef __USE_MINGW_ANSI_STDIO
73# undef __USE_MINGW_ANSI_STDIO
74#endif
75/* Enable threading extensions on Solaris. */
76#ifndef _POSIX_PTHREAD_SEMANTICS
77# undef _POSIX_PTHREAD_SEMANTICS
78#endif
79/* Enable extensions on HP NonStop. */
80#ifndef _TANDEM_SOURCE
81# undef _TANDEM_SOURCE
82#endif
83/* Enable X/Open extensions if necessary. HP-UX 11.11 defines
84 mbstate_t only if _XOPEN_SOURCE is defined to 500, regardless of
85 whether compiling with -Ae or -D_HPUX_SOURCE=1. */
86#ifndef _XOPEN_SOURCE
87# undef _XOPEN_SOURCE
88#endif
89/* Enable general extensions on Solaris. */
90#ifndef __EXTENSIONS__
91# undef __EXTENSIONS__
92#endif
93])
94 AC_CACHE_CHECK([whether it is safe to define __EXTENSIONS__],
95 [ac_cv_safe_to_define___extensions__],
96 [AC_COMPILE_IFELSE(
97 [AC_LANG_PROGRAM([[
98# define __EXTENSIONS__ 1
99 ]AC_INCLUDES_DEFAULT])],
100 [ac_cv_safe_to_define___extensions__=yes],
101 [ac_cv_safe_to_define___extensions__=no])])
102 test $ac_cv_safe_to_define___extensions__ = yes &&
103 AC_DEFINE([__EXTENSIONS__])
104 AC_DEFINE([_ALL_SOURCE])
105 AC_DEFINE([_DARWIN_C_SOURCE])
106 AC_DEFINE([_GNU_SOURCE])
107 AC_DEFINE([__USE_MINGW_ANSI_STDIO])
108 AC_DEFINE([_POSIX_PTHREAD_SEMANTICS])
109 AC_DEFINE([_TANDEM_SOURCE])
110 AC_CACHE_CHECK([whether _XOPEN_SOURCE should be defined],
111 [ac_cv_should_define__xopen_source],
112 [ac_cv_should_define__xopen_source=no
113 AC_COMPILE_IFELSE(
114 [AC_LANG_PROGRAM([[
115 #include <wchar.h>
116 mbstate_t x;]])],
117 [],
118 [AC_COMPILE_IFELSE(
119 [AC_LANG_PROGRAM([[
120 #define _XOPEN_SOURCE 500
121 #include <wchar.h>
122 mbstate_t x;]])],
123 [ac_cv_should_define__xopen_source=yes])])])
124 test $ac_cv_should_define__xopen_source = yes &&
125 AC_DEFINE([_XOPEN_SOURCE], [500])
126])# AC_USE_SYSTEM_EXTENSIONS
127
128# gl_USE_SYSTEM_EXTENSIONS
129# ------------------------
130# Enable extensions on systems that normally disable them,
131# typically due to standards-conformance issues.
132AC_DEFUN_ONCE([gl_USE_SYSTEM_EXTENSIONS],
133[
134 dnl Require this macro before AC_USE_SYSTEM_EXTENSIONS.
135 dnl gnulib does not need it. But if it gets required by third-party macros
136 dnl after AC_USE_SYSTEM_EXTENSIONS is required, autoconf 2.62..2.63 emit a
137 dnl warning: "AC_COMPILE_IFELSE was called before AC_USE_SYSTEM_EXTENSIONS".
138 dnl Note: We can do this only for one of the macros AC_AIX, AC_GNU_SOURCE,
139 dnl AC_MINIX. If people still use AC_AIX or AC_MINIX, they are out of luck.
140 AC_REQUIRE([AC_GNU_SOURCE])
141
142 AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
143])
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