init only for __libcpp_is_constant_evaluated

Author: vitalybuka

libcxx/include/__utility/no_destroy.h

@@ -30,7 +30,12 @@ struct __uninitialized_tag {};
 // initialization using __emplace.
 template <class _Tp>
 struct __no_destroy {
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR explicit __no_destroy(__uninitialized_tag) : __obj_() {}
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR explicit __no_destroy(__uninitialized_tag) {
+    if (__libcpp_is_constant_evaluated()) {
+      for (size_t __i = 0; __i != sizeof(__obj_); ++__i)
+        std::construct_at(__obj_ + __i);
+    }
+  }
 
   template <class... _Args>
   _LIBCPP_HIDE_FROM_ABI explicit __no_destroy(_Args&&... __args) {