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#   Copyright (c) 2014, 2015 Google Inc.; contributed by Alexey Sokolov <sokolov@google.com>
31#   Copyright (c) 2015 Paul Norman <penorman@mac.com>
32#
33#   Copying and distribution of this file, with or without modification, are
34#   permitted in any medium without royalty provided the copyright notice
35#   and this notice are preserved. This file is offered as-is, without any
36#   warranty.
37
38#serial 13
39
40m4_define([_AX_CXX_COMPILE_STDCXX_11_testbody], [[
41  template <typename T>
42    struct check
43    {
44      static_assert(sizeof(int) <= sizeof(T), "not big enough");
45    };
46
47    struct Base {
48    virtual void f() {}
49    };
50    struct Child : public Base {
51    virtual void f() override {}
52    };
53
54    typedef check<check<bool>> right_angle_brackets;
55
56    int a;
57    decltype(a) b;
58
59    typedef check<int> check_type;
60    check_type c;
61    check_type&& cr = static_cast<check_type&&>(c);
62
63    auto d = a;
64    auto l = [](){};
65    // Prevent Clang error: unused variable 'l' [-Werror,-Wunused-variable]
66    struct use_l { use_l() { l(); } };
67
68    // http://stackoverflow.com/questions/13728184/template-aliases-and-sfinae
69    // Clang 3.1 fails with headers of libstd++ 4.8.3 when using std::function because of this
70    namespace test_template_alias_sfinae {
71        struct foo {};
72
73        template<typename T>
74        using member = typename T::member_type;
75
76        template<typename T>
77        void func(...) {}
78
79        template<typename T>
80        void func(member<T>*) {}
81
82        void test();
83
84        void test() {
85            func<foo>(0);
86        }
87    }
88
89    // Check for C++11 attribute support
90    void noret [[noreturn]] () { throw 0; }
91]])
92
93AC_DEFUN([AX_CXX_COMPILE_STDCXX_11], [dnl
94  m4_if([$1], [], [],
95        [$1], [ext], [],
96        [$1], [noext], [],
97        [m4_fatal([invalid argument `$1' to AX_CXX_COMPILE_STDCXX_11])])dnl
98  m4_if([$2], [], [ax_cxx_compile_cxx11_required=true],
99        [$2], [mandatory], [ax_cxx_compile_cxx11_required=true],
100        [$2], [optional], [ax_cxx_compile_cxx11_required=false],
101        [m4_fatal([invalid second argument `$2' to AX_CXX_COMPILE_STDCXX_11])])
102  AC_LANG_PUSH([C++])dnl
103  ac_success=no
104  AC_CACHE_CHECK(whether $CXX supports C++11 features by default,
105  ax_cv_cxx_compile_cxx11,
106  [AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody])],
107    [ax_cv_cxx_compile_cxx11=yes],
108    [ax_cv_cxx_compile_cxx11=no])])
109  if test x$ax_cv_cxx_compile_cxx11 = xyes; then
110    ac_success=yes
111  fi
112
113  m4_if([$1], [noext], [], [dnl
114  if test x$ac_success = xno; then
115    for switch in -std=gnu++11 -std=gnu++0x; do
116      cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx11_$switch])
117      AC_CACHE_CHECK(whether $CXX supports C++11 features with $switch,
118                     $cachevar,
119        [ac_save_CXXFLAGS="$CXXFLAGS"
120         CXXFLAGS="$CXXFLAGS $switch"
121         AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody])],
122          [eval $cachevar=yes],
123          [eval $cachevar=no])
124         CXXFLAGS="$ac_save_CXXFLAGS"])
125      if eval test x\$$cachevar = xyes; then
126        CXXFLAGS="$CXXFLAGS $switch"
127        ac_success=yes
128        break
129      fi
130    done
131  fi])
132
133  m4_if([$1], [ext], [], [dnl
134  if test x$ac_success = xno; then
135    dnl HP's aCC needs +std=c++11 according to:
136    dnl http://h21007.www2.hp.com/portal/download/files/unprot/aCxx/PDF_Release_Notes/769149-001.pdf
137    dnl Cray's crayCC needs "-h std=c++11"
138    for switch in -std=c++11 -std=c++0x +std=c++11 "-h std=c++11"; do
139      cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx11_$switch])
140      AC_CACHE_CHECK(whether $CXX supports C++11 features with $switch,
141                     $cachevar,
142        [ac_save_CXXFLAGS="$CXXFLAGS"
143         CXXFLAGS="$CXXFLAGS $switch"
144         AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody])],
145          [eval $cachevar=yes],
146          [eval $cachevar=no])
147         CXXFLAGS="$ac_save_CXXFLAGS"])
148      if eval test x\$$cachevar = xyes; then
149        CXXFLAGS="$CXXFLAGS $switch"
150        ac_success=yes
151        break
152      fi
153    done
154  fi])
155  AC_LANG_POP([C++])
156  if test x$ax_cxx_compile_cxx11_required = xtrue; then
157    if test x$ac_success = xno; then
158      AC_MSG_ERROR([*** A compiler with support for C++11 language features is required.])
159    fi
160  else
161    if test x$ac_success = xno; then
162      HAVE_CXX11=0
163      AC_MSG_NOTICE([No compiler with C++11 support was found])
164    else
165      HAVE_CXX11=1
166      AC_DEFINE(HAVE_CXX11,1,
167                [define if the compiler supports basic C++11 syntax])
168    fi
169
170    AC_SUBST(HAVE_CXX11)
171  fi
172])
173