c++/m4/ax_cxx_compile_stdcxx_14.m4 - toolchain/capnproto - Git at Google

 # ============================================================================
 #  http://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx_11.html
 #  Additionally modified to detect -stdlib by Kenton Varda.
 #  Further modified for C++14 by Kenton Varda.
 # ============================================================================
 #
 # SYNOPSIS
 #
 #   AX_CXX_COMPILE_STDCXX_14([ext|noext])
 #
 # DESCRIPTION
 #
 #   Check for baseline language coverage in the compiler for the C++14
 #   standard; if necessary, add switches to CXXFLAGS to enable support.
 #   Errors out if no mode that supports C++14 baseline syntax can be found.
 #   The argument, if specified, indicates whether you insist on an extended
 #   mode (e.g. -std=gnu++14) or a strict conformance mode (e.g. -std=c++14).
 #   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 <[email protected]>
 #   Copyright (c) 2012 Zack Weinberg <[email protected]>
 #   Copyright (c) 2013 Kenton Varda <[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 1

 m4_define([_AX_CXX_COMPILE_STDCXX_14_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

   // C++14 stuff
   auto deduceReturnType(int i) { return i; }

   auto genericLambda = [](auto x, auto y) { return x + y; };
   auto captureExpressions = [x = 123]() { return x; };

   // Avoid unused variable warnings.
   int foo() {
     return genericLambda(1, 2) + captureExpressions();
   }
 ]])

 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_14], [dnl
   m4_if([$1], [], [],
         [$1], [ext], [],
         [$1], [noext], [],
         [m4_fatal([invalid argument `$1' to AX_CXX_COMPILE_STDCXX_14])])dnl
   AC_LANG_ASSERT([C++])dnl
   ac_success=no
   AC_CACHE_CHECK(whether $CXX supports C++14 features by default,
   ax_cv_cxx_compile_cxx14,
   [AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_14_testbody])],
     [ax_cv_cxx_compile_cxx14=yes],
     [ax_cv_cxx_compile_cxx14=no])])
   if test x$ax_cv_cxx_compile_cxx14 = xyes; then
     ac_success=yes
   fi

   m4_if([$1], [noext], [], [dnl
   if test x$ac_success = xno; then
     for switch in -std=gnu++14 -std=gnu++1y; do
       cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx14_$switch])
       AC_CACHE_CHECK(whether $CXX supports C++14 features with $switch,
                      $cachevar,
         [ac_save_CXX="$CXX"
          CXX="$CXX $switch"
          AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_14_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++14 -std=c++1y; do
       cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx14_$switch])
       AC_CACHE_CHECK(whether $CXX supports C++14 features with $switch,
                      $cachevar,
         [ac_save_CXX="$CXX"
          CXX="$CXX $switch"
          AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_14_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++14 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
 ])
	# ============================================================================
	# http://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx_11.html
	# Additionally modified to detect -stdlib by Kenton Varda.
	# Further modified for C++14 by Kenton Varda.
	# ============================================================================
	#
	# SYNOPSIS
	#
	# AX_CXX_COMPILE_STDCXX_14([ext\|noext])
	#
	# DESCRIPTION
	#
	# Check for baseline language coverage in the compiler for the C++14
	# standard; if necessary, add switches to CXXFLAGS to enable support.
	# Errors out if no mode that supports C++14 baseline syntax can be found.
	# The argument, if specified, indicates whether you insist on an extended
	# mode (e.g. -std=gnu++14) or a strict conformance mode (e.g. -std=c++14).
	# 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 <[email protected]>
	# Copyright (c) 2012 Zack Weinberg <[email protected]>
	# Copyright (c) 2013 Kenton Varda <[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 1

	m4_define([_AX_CXX_COMPILE_STDCXX_14_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

	// C++14 stuff
	auto deduceReturnType(int i) { return i; }

	auto genericLambda = [](auto x, auto y) { return x + y; };
	auto captureExpressions = [x = 123]() { return x; };

	// Avoid unused variable warnings.
	int foo() {
	return genericLambda(1, 2) + captureExpressions();
	}
	]])

	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_14], [dnl
	m4_if([$1], [], [],
	[$1], [ext], [],
	[$1], [noext], [],
	[m4_fatal([invalid argument `$1' to AX_CXX_COMPILE_STDCXX_14])])dnl
	AC_LANG_ASSERT([C++])dnl
	ac_success=no
	AC_CACHE_CHECK(whether $CXX supports C++14 features by default,
	ax_cv_cxx_compile_cxx14,
	[AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_14_testbody])],
	[ax_cv_cxx_compile_cxx14=yes],
	[ax_cv_cxx_compile_cxx14=no])])
	if test x$ax_cv_cxx_compile_cxx14 = xyes; then
	ac_success=yes
	fi

	m4_if([$1], [noext], [], [dnl
	if test x$ac_success = xno; then
	for switch in -std=gnu++14 -std=gnu++1y; do
	cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx14_$switch])
	AC_CACHE_CHECK(whether $CXX supports C++14 features with $switch,
	$cachevar,
	[ac_save_CXX="$CXX"
	CXX="$CXX $switch"
	AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_14_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++14 -std=c++1y; do
	cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx14_$switch])
	AC_CACHE_CHECK(whether $CXX supports C++14 features with $switch,
	$cachevar,
	[ac_save_CXX="$CXX"
	CXX="$CXX $switch"
	AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_14_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++14 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
	])