1# ============================================================================
2#  http://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx_11.html
3# ============================================================================
4#
5# SYNOPSIS
6#
7#   AX_CXX_COMPILE_STDCXX_11([ext|noext],[mandatory|optional])
8#
9# DESCRIPTION
10#
11#   Check for baseline language coverage in the compiler for the C++11
12#   standard; if necessary, add switches to CXXFLAGS to enable support.
13#
14#   The first argument, if specified, indicates whether you insist on an
15#   extended mode (e.g. -std=gnu++11) or a strict conformance mode (e.g.
16#   -std=c++11).  If neither is specified, you get whatever works, with
17#   preference for an extended mode.
18#
19#   The second argument, if specified 'mandatory' or if left unspecified,
20#   indicates that baseline C++11 support is required and that the macro
21#   should error out if no mode with that support is found.  If specified
22#   'optional', then configuration proceeds regardless, after defining
23#   HAVE_CXX11 if and only if a supporting mode is found.
24#
25# LICENSE
26#
27#   Copyright (c) 2008 Benjamin Kosnik <bkoz@redhat.com>
28#   Copyright (c) 2012 Zack Weinberg <zackw@panix.com>
29#   Copyright (c) 2013 Roy Stogner <roystgnr@ices.utexas.edu>
30#
31#   Copying and distribution of this file, with or without modification, are
32#   permitted in any medium without royalty provided the copyright notice
33#   and this notice are preserved. This file is offered as-is, without any
34#   warranty.
35
36#serial 3
37
38m4_define([_AX_CXX_COMPILE_STDCXX_11_testbody], [
39  template <typename T>
40    struct check
41    {
42      static_assert(sizeof(int) <= sizeof(T), "not big enough");
43    };
44
45    typedef check<check<bool>> right_angle_brackets;
46
47    int a;
48    decltype(a) b;
49
50    typedef check<int> check_type;
51    check_type c;
52    check_type&& cr = static_cast<check_type&&>(c);
53
54    auto d = a;
55])
56
57AC_DEFUN([AX_CXX_COMPILE_STDCXX_11], [dnl
58  m4_if([$1], [], [],
59        [$1], [ext], [],
60        [$1], [noext], [],
61        [m4_fatal([invalid argument `$1' to AX_CXX_COMPILE_STDCXX_11])])dnl
62  m4_if([$2], [], [ax_cxx_compile_cxx11_required=true],
63        [$2], [mandatory], [ax_cxx_compile_cxx11_required=true],
64        [$2], [optional], [ax_cxx_compile_cxx11_required=false],
65        [m4_fatal([invalid second argument `$2' to AX_CXX_COMPILE_STDCXX_11])])dnl
66  AC_LANG_PUSH([C++])dnl
67  ac_success=no
68  AC_CACHE_CHECK(whether $CXX supports C++11 features by default,
69  ax_cv_cxx_compile_cxx11,
70  [AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody])],
71    [ax_cv_cxx_compile_cxx11=yes],
72    [ax_cv_cxx_compile_cxx11=no])])
73  if test x$ax_cv_cxx_compile_cxx11 = xyes; then
74    ac_success=yes
75  fi
76
77  m4_if([$1], [noext], [], [dnl
78  if test x$ac_success = xno; then
79    for switch in -std=gnu++11 -std=gnu++0x; do
80      cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx11_$switch])
81      AC_CACHE_CHECK(whether $CXX supports C++11 features with $switch,
82                     $cachevar,
83        [ac_save_CXXFLAGS="$CXXFLAGS"
84         CXXFLAGS="$CXXFLAGS $switch"
85         AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody])],
86          [eval $cachevar=yes],
87          [eval $cachevar=no])
88         CXXFLAGS="$ac_save_CXXFLAGS"])
89      if eval test x\$$cachevar = xyes; then
90        CXXFLAGS="$CXXFLAGS $switch"
91        ac_success=yes
92        break
93      fi
94    done
95  fi])
96
97  m4_if([$1], [ext], [], [dnl
98  if test x$ac_success = xno; then
99    for switch in -std=c++11 -std=c++0x; do
100      cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx11_$switch])
101      AC_CACHE_CHECK(whether $CXX supports C++11 features with $switch,
102                     $cachevar,
103        [ac_save_CXXFLAGS="$CXXFLAGS"
104         CXXFLAGS="$CXXFLAGS $switch"
105         AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody])],
106          [eval $cachevar=yes],
107          [eval $cachevar=no])
108         CXXFLAGS="$ac_save_CXXFLAGS"])
109      if eval test x\$$cachevar = xyes; then
110        CXXFLAGS="$CXXFLAGS $switch"
111        ac_success=yes
112        break
113      fi
114    done
115  fi])
116  AC_LANG_POP([C++])
117  if test x$ax_cxx_compile_cxx11_required = xtrue; then
118    if test x$ac_success = xno; then
119      AC_MSG_ERROR([*** A compiler with support for C++11 language features is required.])
120    fi
121  else
122    if test x$ac_success = xno; then
123      HAVE_CXX11=0
124      AC_MSG_NOTICE([No compiler with C++11 support was found])
125    else
126      HAVE_CXX11=1
127      AC_DEFINE(HAVE_CXX11,1,
128                [define if the compiler supports basic C++11 syntax])
129    fi
130
131    AC_SUBST(HAVE_CXX11)
132  fi
133])
134