在报告C ++ 11功能的可用性时配置脚本不匹配

Question

尝试使用相同版本的gcc（4.4.7）编译一些基因组研究软件的两个版本（一个旧版本，一个新版本）。 configure脚本检查g ++是否支持C ++ 11功能。在旧版本的软件中，当使用-std=gnu++0x测试g ++时，这会通过，而在新版本中，没有任何检查（包括-std=gnu++0x）通过。知道发生了什么事吗？

为旧版软件修剪./configure的输出：

checking whether g++ supports C++11 features by default... no
checking whether g++ supports C++11 features with -std=gnu++11... no
checking whether g++ supports C++11 features with -std=gnu++0x... yes

为新版软件修剪./configure的输出：

checking whether g++ supports C++11 features by default... no
checking whether g++ supports C++11 features with -std=gnu++11... no
checking whether g++ supports C++11 features with -std=gnu++0x... no
checking whether g++ supports C++11 features with -std=c++11... no
checking whether g++ supports C++11 features with -std=c++0x... no
checking whether g++ supports C++11 features with +std=c++11... no
checking whether g++ supports C++11 features with -h std=c++11... no
configure: error: *** A compiler with support for C++11 language features is required.

我不太了解C ++以及配置脚本中的所有内容，但是看看测试发生的地方，有一个更长的（更全面的？）脚本在新版本中进行测试。

旧版配置脚本中的

-std=gnu++0x测试：

    for switch in -std=gnu++11 -std=gnu++0x; do
      cachevar=`$as_echo "ax_cv_cxx_compile_cxx11_$switch" | $as_tr_sh`
      { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CXX supports C++11 features with $switch" >&5
$as_echo_n "checking whether $CXX supports C++11 features with $switch... " >&6; }
if eval "test \"\${$cachevar+set}\"" = set; then :
  $as_echo_n "(cached) " >&6
else
  ac_save_CXXFLAGS="$CXXFLAGS"
         CXXFLAGS="$CXXFLAGS $switch"
         cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h.  */

  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);

    auto d = a;

_ACEOF
if ac_fn_cxx_try_compile "$LINENO"; then :
  eval $cachevar=yes
else
  eval $cachevar=no
fi
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
         CXXFLAGS="$ac_save_CXXFLAGS"
fi
eval ac_res=\$$cachevar
           { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_res" >&5
$as_echo "$ac_res" >&6; }
      if eval test x\$$cachevar = xyes; then
        CXXFLAGS="$CXXFLAGS $switch"
        ac_success=yes
        break
      fi
    done

新版配置脚本中的

-std=gnu++0x测试：

    for switch in -std=gnu++11 -std=gnu++0x; do
      cachevar=`$as_echo "ax_cv_cxx_compile_cxx11_$switch" | $as_tr_sh`
      { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CXX supports C++11 features with $switch" >&5
$as_echo_n "checking whether $CXX supports C++11 features with $switch... " >&6; }
if eval \${$cachevar+:} false; then :
  $as_echo_n "(cached) " >&6
else
  ac_save_CXX="$CXX"
         CXX="$CXX $switch"
         cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h.  */


// If the compiler admits that it is not ready for C++11, why torture it?
// Hopefully, this will speed up the test.

#ifndef __cplusplus

#error "This is not a C++ compiler"

#elif __cplusplus < 201103L

#error "This is not a C++11 compiler"

#else

namespace cxx11
{

  namespace test_static_assert
  {

    template <typename T>
    struct check
    {
      static_assert(sizeof(int) <= sizeof(T), "not big enough");
    };

  }

  namespace test_final_override
  {

    struct Base
    {
      virtual void f() {}
    };

    struct Derived : public Base
    {
      virtual void f() override {}
    };

  }

  namespace test_double_right_angle_brackets
  {

    template < typename T >
    struct check {};

    typedef check<void> single_type;
    typedef check<check<void>> double_type;
    typedef check<check<check<void>>> triple_type;
    typedef check<check<check<check<void>>>> quadruple_type;

  }

  namespace test_decltype
  {

    int
    f()
    {
      int a = 1;
      decltype(a) b = 2;
      return a + b;
    }

  }

  namespace test_type_deduction
  {

    template < typename T1, typename T2 >
    struct is_same
    {
      static const bool value = false;
    };

    template < typename T >
    struct is_same<T, T>
    {
      static const bool value = true;
    };

    template < typename T1, typename T2 >
    auto
    add(T1 a1, T2 a2) -> decltype(a1 + a2)
    {
      return a1 + a2;
    }

    int
    test(const int c, volatile int v)
    {
      static_assert(is_same<int, decltype(0)>::value == true, "");
      static_assert(is_same<int, decltype(c)>::value == false, "");
      static_assert(is_same<int, decltype(v)>::value == false, "");
      auto ac = c;
      auto av = v;
      auto sumi = ac + av + 'x';
      auto sumf = ac + av + 1.0;
      static_assert(is_same<int, decltype(ac)>::value == true, "");
      static_assert(is_same<int, decltype(av)>::value == true, "");
      static_assert(is_same<int, decltype(sumi)>::value == true, "");
      static_assert(is_same<int, decltype(sumf)>::value == false, "");
      static_assert(is_same<int, decltype(add(c, v))>::value == true, "");
      return (sumf > 0.0) ? sumi : add(c, v);
    }

  }

  namespace test_noexcept
  {

    int f() { return 0; }
    int g() noexcept { return 0; }

    static_assert(noexcept(f()) == false, "");
    static_assert(noexcept(g()) == true, "");

  }

  namespace test_constexpr
  {

    template < typename CharT >
    unsigned long constexpr
    strlen_c_r(const CharT *const s, const unsigned long acc) noexcept
    {
      return *s ? strlen_c_r(s + 1, acc + 1) : acc;
    }

    template < typename CharT >
    unsigned long constexpr
    strlen_c(const CharT *const s) noexcept
    {
      return strlen_c_r(s, 0UL);
    }

    static_assert(strlen_c("") == 0UL, "");
    static_assert(strlen_c("1") == 1UL, "");
    static_assert(strlen_c("example") == 7UL, "");
    static_assert(strlen_c("another\0example") == 7UL, "");

  }

  namespace test_rvalue_references
  {

    template < int N >
    struct answer
    {
      static constexpr int value = N;
    };

    answer<1> f(int&)       { return answer<1>(); }
    answer<2> f(const int&) { return answer<2>(); }
    answer<3> f(int&&)      { return answer<3>(); }

    void
    test()
    {
      int i = 0;
      const int c = 0;
      static_assert(decltype(f(i))::value == 1, "");
      static_assert(decltype(f(c))::value == 2, "");
      static_assert(decltype(f(0))::value == 3, "");
    }

  }

  namespace test_uniform_initialization
  {

    struct test
    {
      static const int zero {};
      static const int one {1};
    };

    static_assert(test::zero == 0, "");
    static_assert(test::one == 1, "");

  }

  namespace test_lambdas
  {

    void
    test1()
    {
      auto lambda1 = [](){};
      auto lambda2 = lambda1;
      lambda1();
      lambda2();
    }

    int
    test2()
    {
      auto a = [](int i, int j){ return i + j; }(1, 2);
      auto b = []() -> int { return '0'; }();
      auto c = [=](){ return a + b; }();
      auto d = [&](){ return c; }();
      auto e = [a, &b](int x) mutable {
        const auto identity = [](int y){ return y; };
        for (auto i = 0; i < a; ++i)
          a += b--;
        return x + identity(a + b);
      }(0);
      return a + b + c + d + e;
    }

    int
    test3()
    {
      const auto nullary = [](){ return 0; };
      const auto unary = [](int x){ return x; };
      using nullary_t = decltype(nullary);
      using unary_t = decltype(unary);
      const auto higher1st = [](nullary_t f){ return f(); };
      const auto higher2nd = [unary](nullary_t f1){
        return [unary, f1](unary_t f2){ return f2(unary(f1())); };
      };
      return higher1st(nullary) + higher2nd(nullary)(unary);
    }

  }

  namespace test_variadic_templates
  {

    template <int...>
    struct sum;

    template <int N0, int... N1toN>
    struct sum<N0, N1toN...>
    {
      static constexpr auto value = N0 + sum<N1toN...>::value;
    };

    template <>
    struct sum<>
    {
      static constexpr auto value = 0;
    };

    static_assert(sum<>::value == 0, "");
    static_assert(sum<1>::value == 1, "");
    static_assert(sum<23>::value == 23, "");
    static_assert(sum<1, 2>::value == 3, "");
    static_assert(sum<5, 5, 11>::value == 21, "");
    static_assert(sum<2, 3, 5, 7, 11, 13>::value == 41, "");

  }

  // http://stackoverflow.com/questions/13728184/template-aliases-and-sfinae
  // Clang 3.1 fails with headers of libstd++ 4.8.3 when using std::function
  // because of this.
  namespace test_template_alias_sfinae
  {

    struct foo {};

    template<typename T>
    using member = typename T::member_type;

    template<typename T>
    void func(...) {}

    template<typename T>
    void func(member<T>*) {}

    void test();

    void test() { func<foo>(0); }

  }

}  // namespace cxx11

#endif  // __cplusplus >= 201103L



_ACEOF
if ac_fn_cxx_try_compile "$LINENO"; then :
  eval $cachevar=yes
else
  eval $cachevar=no
fi
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
         CXX="$ac_save_CXX"
fi
eval ac_res=\$$cachevar
           { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_res" >&5
$as_echo "$ac_res" >&6; }
      if eval test x\$$cachevar = xyes; then
        CXX="$CXX $switch"
        if test -n "$CXXCPP" ; then
          CXXCPP="$CXXCPP $switch"
        fi
        ac_success=yes
        break
      fi
    done

（仅供参考，两个版本都可以使用gcc 4.9.2 [使用RHEL 6上的软件集合]进行编译，但对这里发生的事情非常好奇）