From 9cc1ee931b08bd2401c4011459584b05e2a490e5 Mon Sep 17 00:00:00 2001
From: Casey Carter <cacarter@microsoft.com>
Date: Tue, 23 Feb 2021 08:17:12 -0800
Subject: [PATCH] `<memory>`: Guard aligned allocation with __cpp_aligned_new

We introduced a couple of unguarded uses in `<memory>` in #309 "P0674R1 `make_shared` For Arrays".

Fixes DevCom-1346191.
Fixes AB-1283107.
---
 stl/inc/memory | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/stl/inc/memory b/stl/inc/memory
index ae479ece7b..2a3c0cf3ce 100644
--- a/stl/inc/memory
+++ b/stl/inc/memory
@@ -2070,20 +2070,26 @@ template <class _Refc>
 _NODISCARD _Refc* _Allocate_flexible_array(const size_t _Count) {
     const size_t _Bytes     = _Calculate_bytes_for_flexible_array<_Refc, _Check_overflow::_Yes>(_Count);
     constexpr size_t _Align = alignof(_Refc);
-    if constexpr (_Align <= __STDCPP_DEFAULT_NEW_ALIGNMENT__) {
-        return static_cast<_Refc*>(::operator new(_Bytes));
-    } else {
+#ifdef __cpp_aligned_new
+    if constexpr (_Align > __STDCPP_DEFAULT_NEW_ALIGNMENT__) {
         return static_cast<_Refc*>(::operator new (_Bytes, align_val_t{_Align}));
+    } else
+#endif // __cpp_aligned_new
+    {
+        return static_cast<_Refc*>(::operator new(_Bytes));
     }
 }
 
 template <class _Refc>
 void _Deallocate_flexible_array(_Refc* const _Ptr) noexcept {
     constexpr size_t _Align = alignof(_Refc);
-    if constexpr (_Align <= __STDCPP_DEFAULT_NEW_ALIGNMENT__) {
-        ::operator delete(static_cast<void*>(_Ptr));
-    } else {
+#ifdef __cpp_aligned_new
+    if constexpr (_Align > __STDCPP_DEFAULT_NEW_ALIGNMENT__) {
         ::operator delete (static_cast<void*>(_Ptr), align_val_t{_Align});
+    } else
+#endif // __cpp_aligned_new
+    {
+        ::operator delete(static_cast<void*>(_Ptr));
     }
 }