Unblock __cpp_lib_constexpr_dynamic_alloc for all compilers that suppport constexpr allocations

Author: miscco

stl/inc/xmemory

@@ -1274,7 +1274,7 @@ struct _Fake_proxy_ptr_impl { // fake replacement for a container proxy smart po
 
 struct _Basic_container_proxy_ptr12 {
     // smart pointer components for a _Container_proxy * that don't depend on the allocator
-    _Container_proxy* _Ptr;
+    _Container_proxy* _Ptr = nullptr;
 
     constexpr void _Release() noexcept { // disengage this _Basic_container_proxy_ptr12
         _Ptr = nullptr;

stl/inc/yvals_core.h

@@ -1183,10 +1183,9 @@
 #define __cpp_lib_constexpr_algorithms 201806L
 #define __cpp_lib_constexpr_complex    201711L
 
-#if defined(__cpp_constexpr_dynamic_alloc) \
-    && defined(__clang__) // TRANSITION, MSVC support for constexpr dynamic allocation
+#ifdef __cpp_constexpr_dynamic_alloc
 #define __cpp_lib_constexpr_dynamic_alloc 201907L
-#endif // defined(__cpp_constexpr_dynamic_alloc) && defined(__clang__)
+#endif // __cpp_constexpr_dynamic_alloc
 
 #define __cpp_lib_constexpr_functional  201907L
 #define __cpp_lib_constexpr_iterator    201811L

tests/std/tests/VSO_0157762_feature_test_macros/test.compile.pass.cpp

@@ -411,8 +411,7 @@ STATIC_ASSERT(__cpp_lib_constexpr_complex == 201711L);
 #endif
 #endif
 
-#if _HAS_CXX20 && defined(__cpp_constexpr_dynamic_alloc) \
-    && defined(__clang__) // TRANSITION, MSVC support for constexpr dynamic allocation
+#if _HAS_CXX20 && defined(__cpp_constexpr_dynamic_alloc)
 #ifndef __cpp_lib_constexpr_dynamic_alloc
 #error __cpp_lib_constexpr_dynamic_alloc is not defined
 #elif __cpp_lib_constexpr_dynamic_alloc != 201907L