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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])
#
# DESCRIPTION
#
# Check for baseline language coverage in the compiler for the C++11
# standard; if necessary, add switches to CXXFLAGS to enable support.
# Errors out if no mode that supports C++11 baseline syntax can be found.
# The 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.
#
# LICENSE
#
# Copyright (c) 2008 Benjamin Kosnik <bkoz@redhat.com>
# Copyright (c) 2012 Zack Weinberg <zackw@panix.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 1
m4_define([_AX_CXX_COMPILE_STDCXX_11_testbody], [
template <typename T>
struct check
{
static_assert(sizeof(int) <= sizeof(T), "not big enough");
};
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);
])
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
AC_LANG_ASSERT([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 $switch"
ac_success=yes
break
fi
done
fi])
if test x$ac_success = xno; then
AC_MSG_ERROR([*** A compiler with support for C++11 language features is required.])
fi
])
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