[libcxx] Enable noexcept for GCC 4.6 and greater

[EricWF]

Summary

This patch allows GCC 4.6 and above to use noexcept as opposed to throw().

Is it an ABI safe change to suddenly switch on noexcept? I imagine it must be because it's disabled in w/ clang in C++03 but not C++11.

[EricWF]

Woops. I forgot to turn off noexcept support in C++03 mode for GCC.

[mclow.lists]

do we even use _NOEXCEPT_OR_FALSE any more?

[EricWF]

In D15516#311280, @mclow.lists wrote:

do we even use _NOEXCEPT_OR_FALSE any more?

Doesn't look like it.

[mclow.lists]

Other than the _NOEXCEPT_OR_FALSE thing, this LGTM.

include/__config

 #endif // __linux__
 #endif
 
-#if (__has_feature(cxx_noexcept))
-#  define _NOEXCEPT noexcept
-#  define _NOEXCEPT_(x) noexcept(x)
-#  define _NOEXCEPT_OR_FALSE(x) noexcept(x)
-#else
-#  define _NOEXCEPT throw()
-#  define _NOEXCEPT_(x)
-#  define _NOEXCEPT_OR_FALSE(x) false
+#if !(__has_feature(cxx_noexcept))
+#define _LIBCPP_HAS_NO_NOEXCEPT
 #endif
 
 #if __has_feature(underlying_type)

 #endif  // _GNUC_VER < 404
 
 #if _GNUC_VER < 406
+#define _LIBCPP_HAS_NO_NOEXCEPT
 #define _LIBCPP_HAS_NO_NULLPTR
 #endif
 

 #define _LIBCPP_HAS_NO_UNICODE_CHARS
 #define _LIBCPP_HAS_NO_DELETED_FUNCTIONS
 #define _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
+#define _LIBCPP_HAS_NO_NOEXCEPT
 #define __alignof__ __alignof
 #define _LIBCPP_NORETURN __declspec(noreturn)
 #define _LIBCPP_UNUSED
 #define _ALIGNAS(x) __declspec(align(x))
 #define _LIBCPP_HAS_NO_VARIADICS
 
-#define _NOEXCEPT throw ()
-#define _NOEXCEPT_(x)
-#define _NOEXCEPT_OR_FALSE(x) false
+
 
 #define _LIBCPP_BEGIN_NAMESPACE_STD namespace std {
 #define _LIBCPP_END_NAMESPACE_STD  }

 #define _LIBCPP_NORETURN __attribute__((noreturn))
 #define _LIBCPP_UNUSED
 
-#define _NOEXCEPT throw()
-#define _NOEXCEPT_(x)
-#define _NOEXCEPT_OR_FALSE(x) false
-
 #define _LIBCPP_HAS_NO_TEMPLATE_ALIASES
 #define _LIBCPP_HAS_NO_ADVANCED_SFINAE
 #define _LIBCPP_HAS_NO_ALWAYS_INLINE_VARIADICS
 #define _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#define _LIBCPP_HAS_NO_NOEXCEPT
 #define _LIBCPP_HAS_NO_NULLPTR
 #define _LIBCPP_HAS_NO_UNICODE_CHARS
 #define _LIBCPP_HAS_IS_BASE_OF

 
 #endif // __clang__ || __GNUC__ || _MSC_VER || __IBMCPP__
 
+#ifndef _LIBCPP_HAS_NO_NOEXCEPT
+#  define _NOEXCEPT noexcept
+#  define _NOEXCEPT_(x) noexcept(x)
+#  define _NOEXCEPT_OR_FALSE(x) noexcept(x)
+#else
+#  define _NOEXCEPT throw()
+#  define _NOEXCEPT_(x)
+#  define _NOEXCEPT_OR_FALSE(x) false
+#endif
+
 #ifdef _LIBCPP_HAS_NO_UNICODE_CHARS
 typedef unsigned short char16_t;
 typedef unsigned int   char32_t;