c++ - has::std::has_nothrow_default_constructor 被移动/改变了吗？

Question

试图build boost mirror使用 gcc 4.7.2，我遇到了这个错误，但奇怪的是，我看到了 this documentation .

::std::has_nothrow_default_constructor 是否已移动/更改？

In file included from /home/kfeng/src/mirror-lib/include/mirror/type_traits.hpp:20:0,
                 from /home/kfeng/src/mirror-lib/include/mirror/mirror_base.hpp:38,
                 from /home/kfeng/src/mirror-lib/include/mirror/mirror.hpp:16,
                 from /home/kfeng/src/mirror-lib/src/mirror/example/all_member_variables.cpp:10:
/home/kfeng/src/mirror-lib/include/mirror/type_traits/is_default_constructible.hpp:31:2: error: ‘has_nothrow_default_constructor’ is not a member of ‘std’
/home/kfeng/src/mirror-lib/include/mirror/type_traits/is_default_constructible.hpp:28:9: error: parse error in template argument list
/home/kfeng/src/mirror-lib/include/mirror/type_traits/is_default_constructible.hpp:31:43: error: expected ‘{’ before ‘::’ token
/home/kfeng/src/mirror-lib/include/mirror/type_traits/is_default_constructible.hpp:31:51: error: expected initializer before ‘||’ token
In file included from /home/kfeng/src/mirror-lib/include/mirror/type_traits.hpp:21:0,
                 from /home/kfeng/src/mirror-lib/include/mirror/mirror_base.hpp:38,
                 from /home/kfeng/src/mirror-lib/include/mirror/mirror.hpp:16,
                 from /home/kfeng/src/mirror-lib/src/mirror/example/all_member_variables.cpp:10:
/home/kfeng/src/mirror-lib/include/mirror/type_traits/is_copy_constructible.hpp:31:2: error: ‘has_nothrow_copy_constructor’ is not a member of ‘std’
/home/kfeng/src/mirror-lib/include/mirror/type_traits/is_copy_constructible.hpp:28:9: error: parse error in template argument list
/home/kfeng/src/mirror-lib/include/mirror/type_traits/is_copy_constructible.hpp:31:40: error: expected ‘{’ before ‘::’ token
/home/kfeng/src/mirror-lib/include/mirror/type_traits/is_copy_constructible.hpp:31:48: error: expected initializer before ‘||’ token
make[2]: *** [src/mirror/example/CMakeFiles/mirror-all_member_variables.dir/all_member_variables.cpp.o] Error 1
make[1]: *** [src/mirror/example/CMakeFiles/mirror-all_member_variables.dir/all] Error 2
make: *** [all] Error 2

使用 Pubby 下面的注释回答

像这样的东西应该适用于 gcc 4.7.2 - 我会提交一个补丁，让维护者决定如何最好地处理它。

template <typename T>
 struct is_default_constructible
  : std::integral_constant<
        bool,
        ::std::has_trivial_default_constructor<T>::value ||
#if __cplusplus>=201103L 
        ::std::is_nothrow_default_constructible<T>::value ||
#else
        ::std::has_nothrow_default_constructor<T>::value ||
#endif
        mirror::_class::_<T>::has_default_ctr::value>
 { };

Answer 1

在 C++11 中，它被更改为 std::is_nothrow_default_constructible 以与命名更加一致。