[libcxx-commits] [libcxx] [libc++] Make forward_list constexpr as part of P3372R3 (PR #129435)

[Louis Dionne via libcxx-commits]

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@@ -498,48 +508,53 @@ protected:
 
   _LIBCPP_COMPRESSED_PAIR(__begin_node, __before_begin_, __node_allocator, __alloc_);
 
-  _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __before_begin() _NOEXCEPT {
+  _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __before_begin() _NOEXCEPT {
     return pointer_traits<__begin_node_pointer>::pointer_to(__before_begin_);
   }
-  _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __before_begin() const _NOEXCEPT {
-    return pointer_traits<__begin_node_pointer>::pointer_to(const_cast<__begin_node&>(__before_begin_));
+
+  _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __before_begin() const _NOEXCEPT {
+    return pointer_traits<__begin_node_pointer>::pointer_to(
+        *const_cast<__begin_node*>(std::addressof(__before_begin_)));
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ldionne wrote:

We do have tests using `min_allocator`.

https://github.com/llvm/llvm-project/pull/129435