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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 <[email protected]>
+# Copyright (c) 2012 Zack Weinberg <[email protected]>
+# Copyright (c) 2013 Roy Stogner <[email protected]>
+# Copyright (c) 2014, 2015 Google Inc.; contributed by Alexey Sokolov <[email protected]>
+#
+# 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 11
+
+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
+ dnl HP's aCC needs +std=c++11 according to:
+ dnl http://h21007.www2.hp.com/portal/download/files/unprot/aCxx/PDF_Release_Notes/769149-001.pdf
+ for switch in -std=c++11 -std=c++0x +std=c++11; 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
+])
+