From 9fec814a9a1459b88fec7b569db99ccb12d5362b Mon Sep 17 00:00:00 2001
From: Omer Ozarslan <omerfaruko@gmail.com>
Date: Mon, 29 Dec 2025 10:17:12 -0800
Subject: [PATCH] Launder dereferencing type-punned address
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This is a small patch to avoid strict aliasing issues manifested in GCC
I came across a while ago.

The test case was complex and the failing assertion with a matcher was
present only with `-O3`, so I don't have a standalone test. However, I
manually confirmed adding `-fno-strict-aliasing` fixed the issue before
this patch, and `-O3` behaved as intended after this patch without
turning strict-aliasing off.

There is a similar previous change in https://github.com/google/googletest/commit/50ce52016139a4346a94df71249c14c5d286e000.

For the relevant clause from the C++17 standard, refer to below note
from https://timsong-cpp.github.io/cppwp/n4659/basic.life#8:

> [ Note: If these conditions are not met, a pointer to the new object
can be obtained from a pointer that represents the address of its
storage by calling std::launder ([support.dynamic]).  — end note ]
---
 googletest/include/gtest/gtest-matchers.h | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/googletest/include/gtest/gtest-matchers.h b/googletest/include/gtest/gtest-matchers.h
index 08ffbeb9..8631286b 100644
--- a/googletest/include/gtest/gtest-matchers.h
+++ b/googletest/include/gtest/gtest-matchers.h
@@ -42,6 +42,7 @@
 #include <atomic>
 #include <functional>
 #include <memory>
+#include <new>
 #include <ostream>
 #include <string>
 #include <type_traits>
@@ -402,11 +403,9 @@ class [[nodiscard]] MatcherBase : private MatcherDescriberInterface {
   template <typename M, bool = MatcherBase::IsInlined<M>()>
   struct ValuePolicy {
     static const M& Get(const MatcherBase& m) {
-      // When inlined along with Init, need to be explicit to avoid violating
+      // When inlined along with Init, need to be laundered to avoid violating
       // strict aliasing rules.
-      const M* ptr =
-          static_cast<const M*>(static_cast<const void*>(&m.buffer_));
-      return *ptr;
+      return *std::launder(reinterpret_cast<const M*>(&m.buffer_));
     }
     static void Init(MatcherBase& m, M impl) {
       ::new (static_cast<void*>(&m.buffer_)) M(impl);