[compiler-rt] [asan][win][msvc] override new and delete and seperate TUs (PR #68754)

[Martin Storsjö via llvm-commits]

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@@ -0,0 +1,47 @@
+//===-- asan_win_new_array_nothrow_thunk.cc -------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file is a part of AddressSanitizer, an address sanity checker.
+//
+// Windows-specific user-provided new/delete operator detection and fallback.
+//===----------------------------------------------------------------------===//
+#include "asan_win_new_delete_thunk_common.h"
+
+////////////////////////////////////
+// clang-format off
+// new() Fallback Ordering
+//
+// +----------+
+// |new_scalar<---------------+
+// +----^-----+               |
+//      |                     |
+// +----+-------------+  +----+----+
+// |new_scalar_nothrow|  |new_array|
+// +------------------+  +----^----+
+//                            |
+//               +------------+----+
+//               |NEW_ARRAY_NOTHROW|
+//               +-----------------+
+// clang-format on
+
+extern "C" void* __cdecl __asan_new_array_nothrow(size_t size);
+
+// Avoid tailcall optimization to preserve stack frame.
+#pragma optimize("", off)
+void* operator new[](size_t size, std::nothrow_t const&) noexcept {
+  if (__asan_InitDefine<op_new_scalar>::defined &&
+      __asan_InitDefine<op_new_array>::defined) {
+    return __asan_new_array_nothrow(size);
+  }
+
+  try {
+    return operator new[](size);
----------------
mstorsjo wrote:

FYI (somewhat offtopic) I just checked and saw that this implementation here does fall back on the right operator - vcruntime seems to be getting this bit wrong, see https://developercommunity.visualstudio.com/t/vcruntime-nothrow-array-operator-new-fal/10373274 - where it seems that vcruntime's implementation of nothrowing array new falls back on nothrowing scalar new, instead of throwing array new like it's supposed to.

https://github.com/llvm/llvm-project/pull/68754