Mutex: Remove destructor in release build

The Mutex destructor is needed only to clean up debug logging
and invariant checking synch events. These are not supposed
to be used in production, but the non-empty destructor has
costs for production builds.

Instead of removing synch events in destructor,
drop all of them if we accumulated too many.
For tests is should not matter (we maybe only consume
a bit more memory). Production builds should be either unaffected
(if don't use debug logging), or use periodic reset of all synch events.

PiperOrigin-RevId: 578123259
Change-Id: I0ec59183a5f63ea0a6b7fc50f0a77974e7f677be

1 files changed, 27 insertions, 0 deletions

diff --git a/absl/synchronization/mutex_test.cc b/absl/synchronization/mutex_test.cc
index 6c38c07c..35b43334 100644
--- a/absl/synchronization/mutex_test.cc
+++ b/absl/synchronization/mutex_test.cc
@@ -1709,6 +1709,33 @@ TEST(Mutex, Logging) {
   logged_cv.SignalAll();
 }
 
+TEST(Mutex, LoggingAddressReuse) {
+  // Repeatedly re-create a Mutex with debug logging at the same address.
+  alignas(absl::Mutex) char storage[sizeof(absl::Mutex)];
+  auto invariant =
+      +[](void *alive) { EXPECT_TRUE(*static_cast<bool *>(alive)); };
+  constexpr size_t kIters = 10;
+  bool alive[kIters] = {};
+  for (size_t i = 0; i < kIters; ++i) {
+    absl::Mutex *mu = new (storage) absl::Mutex;
+    alive[i] = true;
+    mu->EnableDebugLog("Mutex");
+    mu->EnableInvariantDebugging(invariant, &alive[i]);
+    mu->Lock();
+    mu->Unlock();
+    mu->~Mutex();
+    alive[i] = false;
+  }
+}
+
+TEST(Mutex, LoggingBankrupcy) {
+  // Test the case with too many live Mutexes with debug logging.
+  std::vector<absl::Mutex> mus(1 << 20);
+  for (auto &mu : mus) {
+    mu.EnableDebugLog("Mutex");
+  }
+}
+
 // --------------------------------------------------------
 
 // Generate the vector of thread counts for tests parameterized on thread count.