ax_cxx_compile_stdcxx_14.m4 (7053B)
1 # ============================================================================ 2 # http://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx_11.html 3 # Additionally modified to detect -stdlib by Kenton Varda. 4 # Further modified for C++14 by Kenton Varda. 5 # ============================================================================ 6 # 7 # SYNOPSIS 8 # 9 # AX_CXX_COMPILE_STDCXX_14([ext|noext]) 10 # 11 # DESCRIPTION 12 # 13 # Check for baseline language coverage in the compiler for the C++14 14 # standard; if necessary, add switches to CXXFLAGS to enable support. 15 # Errors out if no mode that supports C++14 baseline syntax can be found. 16 # The argument, if specified, indicates whether you insist on an extended 17 # mode (e.g. -std=gnu++14) or a strict conformance mode (e.g. -std=c++14). 18 # If neither is specified, you get whatever works, with preference for an 19 # extended mode. 20 # 21 # Additionally, check if the standard library supports C++11. If not, 22 # try adding -stdlib=libc++ to see if that fixes it. This is needed e.g. 23 # on Mac OSX 10.8, which ships with a very old libstdc++ but a relatively 24 # new libc++. 25 # 26 # Both flags are actually added to CXX rather than CXXFLAGS to work around 27 # a bug in libtool: -stdlib is stripped from CXXFLAGS when linking dynamic 28 # libraries because it is not recognized. A patch was committed to mainline 29 # libtool in February 2012 but as of June 2013 there has not yet been a 30 # release containing this patch. 31 # http://git.savannah.gnu.org/gitweb/?p=libtool.git;a=commit;h=c0c49f289f22ae670066657c60905986da3b555f 32 # 33 # LICENSE 34 # 35 # Copyright (c) 2008 Benjamin Kosnik <bkoz@redhat.com> 36 # Copyright (c) 2012 Zack Weinberg <zackw@panix.com> 37 # Copyright (c) 2013 Kenton Varda <temporal@gmail.com> 38 # 39 # Copying and distribution of this file, with or without modification, are 40 # permitted in any medium without royalty provided the copyright notice 41 # and this notice are preserved. This file is offered as-is, without any 42 # warranty. 43 44 #serial 1 45 46 m4_define([_AX_CXX_COMPILE_STDCXX_14_testbody], [[ 47 template <typename T> 48 struct check 49 { 50 static_assert(sizeof(int) <= sizeof(T), "not big enough"); 51 }; 52 53 typedef check<check<bool>> right_angle_brackets; 54 55 int a; 56 decltype(a) b; 57 58 typedef check<int> check_type; 59 check_type c; 60 check_type&& cr = static_cast<check_type&&>(c); 61 62 // GCC 4.7 introduced __float128 and makes reference to it in type_traits. 63 // Clang doesn't implement it, so produces an error. Using -std=c++11 64 // instead of -std=gnu++11 works around the problem. But on some 65 // platforms we need -std=gnu++11. So we want to make sure the test of 66 // -std=gnu++11 fails only where this problem is present, and we hope that 67 // -std=c++11 is always an acceptable fallback in these cases. Complicating 68 // matters, though, is that we don't want to fail here if the platform is 69 // completely missing a C++11 standard library, because we want to probe that 70 // in a later test. It happens, though, that Clang allows us to check 71 // whether a header exists at all before we include it. 72 // 73 // So, if we detect that __has_include is available (which it is on Clang), 74 // and we use it to detect that <type_traits> (a C++11 header) exists, then 75 // we go ahead and #include it to see if it breaks. In all other cases, we 76 // don't #include it at all. 77 #ifdef __has_include 78 #if __has_include(<type_traits>) 79 #include <type_traits> 80 #endif 81 #endif 82 83 // C++14 stuff 84 auto deduceReturnType(int i) { return i; } 85 86 auto genericLambda = [](auto x, auto y) { return x + y; }; 87 auto captureExpressions = [x = 123]() { return x; }; 88 89 // Avoid unused variable warnings. 90 int foo() { 91 return genericLambda(1, 2) + captureExpressions(); 92 } 93 ]]) 94 95 m4_define([_AX_CXX_COMPILE_STDCXX_11_testbody_lib], [ 96 #include <initializer_list> 97 #include <unordered_map> 98 #include <atomic> 99 #include <thread> 100 ]) 101 102 AC_DEFUN([AX_CXX_COMPILE_STDCXX_14], [dnl 103 m4_if([$1], [], [], 104 [$1], [ext], [], 105 [$1], [noext], [], 106 [m4_fatal([invalid argument `$1' to AX_CXX_COMPILE_STDCXX_14])])dnl 107 AC_LANG_ASSERT([C++])dnl 108 ac_success=no 109 AC_CACHE_CHECK(whether $CXX supports C++14 features by default, 110 ax_cv_cxx_compile_cxx14, 111 [AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_14_testbody])], 112 [ax_cv_cxx_compile_cxx14=yes], 113 [ax_cv_cxx_compile_cxx14=no])]) 114 if test x$ax_cv_cxx_compile_cxx14 = xyes; then 115 ac_success=yes 116 fi 117 118 m4_if([$1], [noext], [], [dnl 119 if test x$ac_success = xno; then 120 for switch in -std=gnu++14 -std=gnu++1y; do 121 cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx14_$switch]) 122 AC_CACHE_CHECK(whether $CXX supports C++14 features with $switch, 123 $cachevar, 124 [ac_save_CXX="$CXX" 125 CXX="$CXX $switch" 126 AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_14_testbody])], 127 [eval $cachevar=yes], 128 [eval $cachevar=no]) 129 CXX="$ac_save_CXX"]) 130 if eval test x\$$cachevar = xyes; then 131 CXX="$CXX $switch" 132 ac_success=yes 133 break 134 fi 135 done 136 fi]) 137 138 m4_if([$1], [ext], [], [dnl 139 if test x$ac_success = xno; then 140 for switch in -std=c++14 -std=c++1y; do 141 cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx14_$switch]) 142 AC_CACHE_CHECK(whether $CXX supports C++14 features with $switch, 143 $cachevar, 144 [ac_save_CXX="$CXX" 145 CXX="$CXX $switch" 146 AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_14_testbody])], 147 [eval $cachevar=yes], 148 [eval $cachevar=no]) 149 CXX="$ac_save_CXX"]) 150 if eval test x\$$cachevar = xyes; then 151 CXX="$CXX $switch" 152 ac_success=yes 153 break 154 fi 155 done 156 fi]) 157 158 if test x$ac_success = xno; then 159 AC_MSG_ERROR([*** A compiler with support for C++14 language features is required.]) 160 else 161 ac_success=no 162 AC_CACHE_CHECK(whether $CXX supports C++11 library features by default, 163 ax_cv_cxx_compile_cxx11_lib, 164 [AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody_lib])], 165 [ax_cv_cxx_compile_cxx11_lib=yes], 166 [ax_cv_cxx_compile_cxx11_lib=no]) 167 ]) 168 if test x$ax_cv_cxx_compile_cxx11_lib = xyes; then 169 ac_success=yes 170 else 171 # Try with -stdlib=libc++ 172 AC_CACHE_CHECK(whether $CXX supports C++11 library features with -stdlib=libc++, 173 ax_cv_cxx_compile_cxx11_lib_libcxx, 174 [ac_save_CXX="$CXX" 175 CXX="$CXX -stdlib=libc++" 176 AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody_lib])], 177 [eval ax_cv_cxx_compile_cxx11_lib_libcxx=yes], 178 [eval ax_cv_cxx_compile_cxx11_lib_libcxx=no]) 179 CXX="$ac_save_CXX"]) 180 if eval test x$ax_cv_cxx_compile_cxx11_lib_libcxx = xyes; then 181 CXX="$CXX -stdlib=libc++" 182 ac_success=yes 183 break 184 fi 185 fi 186 187 if test x$ac_success = xno; then 188 AC_MSG_ERROR([*** A C++ library with support for C++11 features is required.]) 189 fi 190 fi 191 ])