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[libc++] Fix failure with GCC 15 (#117319) #117322

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[libc++] Fix failure with GCC 15 (#117319) #117322

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2 changes: 1 addition & 1 deletion libcxx/include/__type_traits/decay.h
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Original file line number Diff line number Diff line change
Expand Up @@ -25,7 +25,7 @@

_LIBCPP_BEGIN_NAMESPACE_STD

#if __has_builtin(__decay)
#if __has_builtin(__decay) && !defined(_LIBCPP_COMPILER_GCC)
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@ldionne ldionne Nov 22, 2024

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How is the GCC-provided builtin incompatible with Clang's?

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@philnik777 philnik777 Nov 22, 2024

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GCC doesn't mangle the builtin.

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@ldionne ldionne Nov 22, 2024

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Ah, so do we need to do something like

template <class _Tp>
struct __decay_impl {
  using type = __builtin_decay_t(_Tp);
};

template <class _Tp>
using __decay_t = typename __decay_impl<_Tp>::type;

?

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@killcerr killcerr Nov 22, 2024 •
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I use the same way in similar issue
to fix this issue.

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@philnik777 philnik777 Nov 22, 2024

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Yes, something like that. I'd probably just use decay as the base (i.e. using __decay_t = decay<T>::type) for GCC.

template <class _Tp>
using __decay_t _LIBCPP_NODEBUG = __decay(_Tp);

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