[libcxx-commits] [libcxx] [libc++] make std::atomic works with types with paddings (PR #76180)

[Mark de Wever via libcxx-commits]

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@@ -26,6 +27,32 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+template <class _Tp>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR void __clear_padding_if_needed(_Tp* __ptr) noexcept {
+#if _LIBCPP_STD_VER >= 20
+  constexpr bool __needs_clear_padding =
+      !__has_unique_object_representations(_Tp) && !is_same<_Tp, float>::value && !is_same<_Tp, double>::value;
+  if constexpr (__needs_clear_padding) {
+    if (!__builtin_is_constant_evaluated()) {
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mordante wrote:

why not `std::is_constant_evaluated`?

https://github.com/llvm/llvm-project/pull/76180