[libcxx-commits] [libcxx] [libc++] Implement P0493R5: Atomic minimum/maximum (PR #180333)

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@@ -259,6 +261,77 @@ __cxx_atomic_fetch_xor(__cxx_atomic_base_impl<_Tp>* __a, _Tp __pattern, memory_o
       std::addressof(__a->__a_value), __pattern, static_cast<__memory_order_underlying_t>(__order));
 }
 
+// Clang's __c11_atomic_fetch_max/min builtins do not accept pointer
+// arguments, so dispatch to a CAS loop for pointer types.
+// TODO: Use the builtin for pointer types once Clang accepts them.
+template <class _Tp, __enable_if_t<!is_pointer<_Tp>::value, int> = 0>
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c8ef wrote:

> if one day clang adds the support for pointer fetch min/max, we don't need to change any code here as the concept will detect it

On second thought, this also means we currently lack test coverage for the built-in branch guarded by `if constexpr`. Because of this, I’d prefer to hold off on adding it for now. We can add it manually once our CI includes compilers that actually support it.


https://github.com/llvm/llvm-project/pull/180333