# ============================================================================ # http://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx_11.html # Additionally modified to detect -stdlib by Kenton Varda. # ============================================================================ # # 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. # # Additionally, check if the standard library supports C++11. If not, # try adding -stdlib=libc++ to see if that fixes it. This is needed e.g. # on Mac OSX 10.8, which ships with a very old libstdc++ but a relatively # new libc++. # # Both flags are actually added to CXX rather than CXXFLAGS to work around # a bug in libtool: -stdlib is stripped from CXXFLAGS when linking dynamic # libraries because it is not recognized. A patch was committed to mainline # libtool in February 2012 but as of June 2013 there has not yet been a # release containing this patch. # http://git.savannah.gnu.org/gitweb/?p=libtool.git;a=commit;h=c0c49f289f22ae670066657c60905986da3b555f # # LICENSE # # Copyright (c) 2008 Benjamin Kosnik <bkoz@redhat.com> # Copyright (c) 2012 Zack Weinberg <zackw@panix.com> # Copyright (c) 2013 Kenton Varda <temporal@gmail.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); // GCC 4.7 introduced __float128 and makes reference to it in type_traits. // Clang doesn't implement it, so produces an error. Using -std=c++11 // instead of -std=gnu++11 works around the problem. But on some // platforms we need -std=gnu++11. So we want to make sure the test of // -std=gnu++11 fails only where this problem is present, and we hope that // -std=c++11 is always an acceptable fallback in these cases. Complicating // matters, though, is that we don't want to fail here if the platform is // completely missing a C++11 standard library, because we want to probe that // in a later test. It happens, though, that Clang allows us to check // whether a header exists at all before we include it. // // So, if we detect that __has_include is available (which it is on Clang), // and we use it to detect that <type_traits> (a C++11 header) exists, then // we go ahead and #include it to see if it breaks. In all other cases, we // don't #include it at all. #ifdef __has_include #if __has_include(<type_traits>) #include <type_traits> #endif #endif ]) m4_define([_AX_CXX_COMPILE_STDCXX_11_testbody_lib], [ #include <initializer_list> #include <unordered_map> #include <atomic> #include <thread> ]) 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, $cachevar, [ac_save_CXX="$CXX" CXX="$CXX $switch" AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody])], [eval $cachevar=yes], [eval $cachevar=no]) CXX="$ac_save_CXX"]) if eval test x\$$cachevar = xyes; then CXX="$CXX $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, $cachevar, [ac_save_CXX="$CXX" CXX="$CXX $switch" AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody])], [eval $cachevar=yes], [eval $cachevar=no]) CXX="$ac_save_CXX"]) if eval test x\$$cachevar = xyes; then CXX="$CXX $switch" ac_success=yes break fi done fi]) if test x$ac_success = xno; then AC_MSG_ERROR([*** A compiler with support for C++11 language features is required.]) else ac_success=no AC_CACHE_CHECK(whether $CXX supports C++11 library features by default, ax_cv_cxx_compile_cxx11_lib, [AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody_lib])], [ax_cv_cxx_compile_cxx11_lib=yes], [ax_cv_cxx_compile_cxx11_lib=no]) ]) if test x$ax_cv_cxx_compile_cxx11_lib = xyes; then ac_success=yes else # Try with -stdlib=libc++ AC_CACHE_CHECK(whether $CXX supports C++11 library features with -stdlib=libc++, ax_cv_cxx_compile_cxx11_lib_libcxx, [ac_save_CXX="$CXX" CXX="$CXX -stdlib=libc++" AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody_lib])], [eval ax_cv_cxx_compile_cxx11_lib_libcxx=yes], [eval ax_cv_cxx_compile_cxx11_lib_libcxx=no]) CXX="$ac_save_CXX"]) if eval test x$ax_cv_cxx_compile_cxx11_lib_libcxx = xyes; then CXX="$CXX -stdlib=libc++" ac_success=yes break fi fi if test x$ac_success = xno; then AC_MSG_ERROR([*** A C++ library with support for C++11 features is required.]) fi fi ])