[libcxx-commits] [libcxx] [libc++] Remove UB from std::map __tree_node construction (PR #153908)

[Vinay Deshmukh via libcxx-commits]

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@@ -1808,7 +1842,7 @@ typename __tree<_Tp, _Compare, _Allocator>::__node_holder
 __tree<_Tp, _Compare, _Allocator>::__construct_node(_Args&&... __args) {
   __node_allocator& __na = __node_alloc();
   __node_holder __h(__node_traits::allocate(__na, 1), _Dp(__na));
-  __node_traits::construct(__na, std::addressof(__h->__value_), std::forward<_Args>(__args)...);
+  std::__construct_at(std::addressof(*__h), __na, std::forward<_Args>(__args)...);
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vinay-deshmukh wrote:

N.B. This is the line that prompts this change due to needing workarounds when implementing P3372 for map (Add `constexpr`)

https://github.com/llvm/llvm-project/pull/153908