Add `extern "C"` to header
[argpar.git] / m4 / ac_extensions.m4
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__).
38 AC_DEFUN_ONCE([AC_USE_SYSTEM_EXTENSIONS],
39 [AC_BEFORE([$0], [AC_COMPILE_IFELSE])dnl
40 AC_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
56 dnl Use a different key than __EXTENSIONS__, as that name broke existing
57 dnl 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.
132 AC_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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