Question

I’m trying to port buildsystem of my project to GNU autotools. The code need to be compiled with -std=c++11 or -std=c++0x flag. I want my configure script to check if compiler supports C++11 or not. I tried adding AX_CHECK_COMPILE_FLAG([-std=c++0x], [CXXFLAGS="$CXXFLAGS -std=c++0x"]) to configure.ac file but configure fails with this error:

 ...
./configure: line 2732: syntax error near unexpected token `-std=c++0x,'
./configure: line 2732: `AX_CHECK_COMPILE_FLAG(-std=c++0x, CXXFLAGS="$CXXFLAGS -std=c++0x")'

Answer 1

Hopefully there will be more comprehensive support for C++11 in future autoconf releases. In the mean time, I use a C++11 source test from ax_cxx_compile_stdcxx_11.m4 in the GNU autoconf archive:

AC_PROG_CXX
AC_LANG_PUSH([C++])

AC_COMPILE_IFELSE([AC_LANG_SOURCE(
  [[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);]])],,
  AC_MSG_FAILURE(['$CXX $CXXFLAGS' does not accept ISO C++11]))