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# ============================================================================
# http://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx_11.html
# ============================================================================
#
# SYNOPSIS
#
# AX_CXX_COMPILE_STDCXX_11([ext|noext],[mandatory|optional])
#
# DESCRIPTION
#
# Check for baseline language coverage in the compiler for the C++11
# standard; if necessary, add switches to CXXFLAGS to enable support.
#
# The first argument, if specified, indicates whether you insist on an
# extended mode (e.g. -std=gnu++11) or a strict conformance mode (e.g.
# -std=c++11). If neither is specified, you get whatever works, with
# preference for an extended mode.
#
# The second argument, if specified 'mandatory' or if left unspecified,
# indicates that baseline C++11 support is required and that the macro
# should error out if no mode with that support is found. If specified
# 'optional', then configuration proceeds regardless, after defining
# HAVE_CXX11 if and only if a supporting mode is found.
#
# LICENSE
#
# Copyright (c) 2008 Benjamin Kosnik <bkoz@redhat.com>
# Copyright (c) 2012 Zack Weinberg <zackw@panix.com>
# Copyright (c) 2013 Roy Stogner <roystgnr@ices.utexas.edu>
# Copyright (c) 2014, 2015 Google Inc.; contributed by Alexey Sokolov <sokolov@google.com>
#
# Copying and distribution of this file, with or without modification, are
# permitted in any medium without royalty provided the copyright notice
# and this notice are preserved. This file is offered as-is, without any
# warranty.
#serial 10
m4_define([_AX_CXX_COMPILE_STDCXX_11_testbody], [[
template <typename T>
struct check
{
static_assert(sizeof(int) <= sizeof(T), "not big enough");
};
struct Base {
virtual void f() {}
};
struct Child : public Base {
virtual void f() override {}
};
typedef check<check<bool>> right_angle_brackets;
int a;
decltype(a) b;
typedef check<int> check_type;
check_type c;
check_type&& cr = static_cast<check_type&&>(c);
auto d = a;
auto l = [](){};
// Prevent Clang error: unused variable 'l' [-Werror,-Wunused-variable]
struct use_l { use_l() { l(); } };
// http://stackoverflow.com/questions/13728184/template-aliases-and-sfinae
// Clang 3.1 fails with headers of libstd++ 4.8.3 when using std::function because of this
namespace test_template_alias_sfinae {
struct foo {};
template<typename T>
using member = typename T::member_type;
template<typename T>
void func(...) {}
template<typename T>
void func(member<T>*) {}
void test();
void test() {
func<foo>(0);
}
}
]])
AC_DEFUN([AX_CXX_COMPILE_STDCXX_11], [dnl
m4_if([$1], [], [],
[$1], [ext], [],
[$1], [noext], [],
[m4_fatal([invalid argument `$1' to AX_CXX_COMPILE_STDCXX_11])])dnl
m4_if([$2], [], [ax_cxx_compile_cxx11_required=true],
[$2], [mandatory], [ax_cxx_compile_cxx11_required=true],
[$2], [optional], [ax_cxx_compile_cxx11_required=false],
[m4_fatal([invalid second argument `$2' to AX_CXX_COMPILE_STDCXX_11])])
AC_LANG_PUSH([C++])dnl
ac_success=no
AC_CACHE_CHECK(whether $CXX supports C++11 features by default,
ax_cv_cxx_compile_cxx11,
[AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody])],
[ax_cv_cxx_compile_cxx11=yes],
[ax_cv_cxx_compile_cxx11=no])])
if test x$ax_cv_cxx_compile_cxx11 = xyes; then
ac_success=yes
fi
m4_if([$1], [noext], [], [dnl
if test x$ac_success = xno; then
for switch in -std=gnu++11 -std=gnu++0x; do
cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx11_$switch])
AC_CACHE_CHECK(whether $CXX supports C++11 features with $switch,
$cachevar,
[ac_save_CXXFLAGS="$CXXFLAGS"
CXXFLAGS="$CXXFLAGS $switch"
AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody])],
[eval $cachevar=yes],
[eval $cachevar=no])
CXXFLAGS="$ac_save_CXXFLAGS"])
if eval test x\$$cachevar = xyes; then
CXXFLAGS="$CXXFLAGS $switch"
ac_success=yes
break
fi
done
fi])
m4_if([$1], [ext], [], [dnl
if test x$ac_success = xno; then
for switch in -std=c++11 -std=c++0x; do
cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx11_$switch])
AC_CACHE_CHECK(whether $CXX supports C++11 features with $switch,
$cachevar,
[ac_save_CXXFLAGS="$CXXFLAGS"
CXXFLAGS="$CXXFLAGS $switch"
AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody])],
[eval $cachevar=yes],
[eval $cachevar=no])
CXXFLAGS="$ac_save_CXXFLAGS"])
if eval test x\$$cachevar = xyes; then
CXXFLAGS="$CXXFLAGS $switch"
ac_success=yes
break
fi
done
fi])
AC_LANG_POP([C++])
if test x$ax_cxx_compile_cxx11_required = xtrue; then
if test x$ac_success = xno; then
AC_MSG_ERROR([*** A compiler with support for C++11 language features is required.])
fi
else
if test x$ac_success = xno; then
HAVE_CXX11=0
AC_MSG_NOTICE([No compiler with C++11 support was found])
else
HAVE_CXX11=1
AC_DEFINE(HAVE_CXX11,1,
[define if the compiler supports basic C++11 syntax])
fi
AC_SUBST(HAVE_CXX11)
fi
])
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