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libstdc++: Guard use of new built-in with __has_builtin

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I forgot that non-GCC compilers don't have this built-in yet.

For Clang we could do something like the check below (as described in
P2255), but for now I'm just fixing the regression.

 #if __has_builtin((__reference_binds_to_temporary)
  bool _Dangle = __reference_binds_to_temporary(_Tp, _Res_t)
                 && __and_<is_reference<_Tp>,
                           __not_<is_reference<_Res_t>>,
                           is_convertible<__remove_cvref_t<_Res_t>*,
                                          __remove_cvref_t<_Tp>*>>::value
 #endif

libstdc++-v3/ChangeLog:

	* include/std/type_traits (__is_invocable_impl): Check
	__has_builtin(__reference_converts_from_temporary) before using
	built-in.
This commit is contained in:
Jonathan Wakely 2022-09-29 11:30:05 +01:00
parent a1f7f9541c
commit df7f273650
1 changed files with 6 additions and 1 deletions
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7
libstdc++-v3/include/std/type_traits
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@ -2901,7 +2901,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Tp,
bool _Nothrow = noexcept(_S_conv<_Tp>(_S_get())),
typename = decltype(_S_conv<_Tp>(_S_get())),
bool _Dangle = __reference_converts_from_temporary(_Tp, _Res_t)>
#if __has_builtin(__reference_converts_from_temporary)
bool _Dangle = __reference_converts_from_temporary(_Tp, _Res_t)
#else
bool _Dangle = false
#endif
>
static __bool_constant<_Nothrow && !_Dangle>
_S_test(int);