AC_DEFUN([AX_GCC_OPTION], [
AC_REQUIRE([AC_PROG_CC])

AC_MSG_CHECKING([if gcc accepts $1 option])

AS_IF([ test "x$GCC" = "xyes" ],[
AS_IF([ test -z "$3" ],[
ax_gcc_option_test="int main()
{
return 0;
}"
],[
ax_gcc_option_test="$3"
])

# Dump the test program to file
cat <<EOF > conftest.c
$ax_gcc_option_test
EOF

# Dump back the file to the log, useful for debugging purposes
AC_TRY_COMMAND(cat conftest.c 1>&AS_MESSAGE_LOG_FD)

AS_IF([ AC_TRY_COMMAND($CC $2 $1 -c conftest.c 1>&AS_MESSAGE_LOG_FD) ],[
AC_MSG_RESULT([yes])
$4
],[
AC_MSG_RESULT([no])
$5
])
],[
AC_MSG_RESULT([no gcc available])
])
])

AC_DEFUN([AX_GCC_VERSION], [
GCC_VERSION=""
AX_GCC_OPTION([-dumpversion],[],[],[
ax_gcc_version_option=yes
],[
ax_gcc_version_option=no
])
AS_IF([test "x$GCC" = "xyes"],[
AS_IF([test "x$ax_gcc_version_option" != "xno"],[
AC_CACHE_CHECK([gcc version],[ax_cv_gcc_version],[
ax_cv_gcc_version="`$CC -dumpversion`"
AS_IF([test "x$ax_cv_gcc_version" = "x"],[
ax_cv_gcc_version=""
])
])
GCC_VERSION=$ax_cv_gcc_version
])
])
AC_SUBST([GCC_VERSION])
])

AC_DEFUN([AX_GXX_VERSION], [
GXX_VERSION=""
AX_GCC_OPTION([-dumpversion],[],[],[
ax_gcc_version_option=yes
],[
ax_gcc_version_option=no
])
AS_IF([test "x$GXX" = "xyes"],[
AS_IF([test "x$ax_gxx_version_option" != "no"],[
AC_CACHE_CHECK([gxx version],[ax_cv_gxx_version],[
ax_cv_gxx_version="`$CXX -dumpversion`"
AS_IF([test "x$ax_cv_gxx_version" = "x"],[
ax_cv_gxx_version=""
])
])
GXX_VERSION=$ax_cv_gxx_version
])
])
AC_SUBST([GXX_VERSION])
])

AC_DEFUN([AX_COMPILER_VENDOR],
[
AC_CACHE_CHECK([for _AC_LANG compiler vendor], ax_cv_[]_AC_LANG_ABBREV[]_compiler_vendor,
[ax_cv_[]_AC_LANG_ABBREV[]_compiler_vendor=unknown
# note: don't check for gcc first since some other compilers define __GNUC__
for ventest in intel:__ICC,__ECC,__INTEL_COMPILER ibm:__xlc__,__xlC__,__IBMC__,__IBMCPP__ pathscale:__PATHCC__,__PATHSCALE__ gnu:__GNUC__ sun:__SUNPRO_C,__SUNPRO_CC hp:__HP_cc,__HP_aCC dec:__DECC,__DECCXX,__DECC_VER,__DECCXX_VER borland:__BORLANDC__,__TURBOC__ comeau:__COMO__ cray:_CRAYC kai:__KCC lcc:__LCC__ metrowerks:__MWERKS__ sgi:__sgi,sgi microsoft:_MSC_VER watcom:__WATCOMC__ portland:__PGI; do
vencpp="defined("`echo $ventest | cut -d: -f2 | sed 's/,/) || defined(/g'`")"
AC_COMPILE_IFELSE([AC_LANG_PROGRAM(,[
#if !($vencpp)
thisisanerror;
#endif
])], [ax_cv_]_AC_LANG_ABBREV[_compiler_vendor=`echo $ventest | cut -d: -f1`; break])
done
])
])

# ============================================================================
#  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 <bkoz@redhat.com>
#   Copyright (c) 2012 Zack Weinberg <zackw@panix.com>
#   Copyright (c) 2013 Roy Stogner <roystgnr@ices.utexas.edu>
#   Copyright (c) 2014 Alexey Sokolov <sokolov@google.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.

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 = [](){};
]])

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
    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 $switch"
        ac_success=yes
        break
      fi
    done
  fi])
  AC_LANG_POP([C++])
  if test x$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
])