Googletest export

googletest/test/googletest-port-test.cc

@@ -289,36 +289,61 @@ void* ThreadFunc(void* data) {
 }
 
 TEST(GetThreadCountTest, ReturnsCorrectValue) {
-  const size_t starting_count = GetThreadCount();
-  pthread_t       thread_id;
+  size_t starting_count;
+  size_t thread_count_after_create;
+  size_t thread_count_after_join;
+
+  // We can't guarantee that no other thread was created or destroyed between
+  // any two calls to GetThreadCount(). We make multiple attempts, hoping that
+  // background noise is not constant and we would see the "right" values at
+  // some point.
+  for (int attempt = 0; attempt < 20; ++attempt) {
+    starting_count = GetThreadCount();
+    pthread_t thread_id;
+
+    internal::Mutex mutex;
+    {
+      internal::MutexLock lock(&mutex);
+      pthread_attr_t attr;
+      ASSERT_EQ(0, pthread_attr_init(&attr));
+      ASSERT_EQ(0, pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE));
+
+      const int status = pthread_create(&thread_id, &attr, &ThreadFunc, &mutex);
+      ASSERT_EQ(0, pthread_attr_destroy(&attr));
+      ASSERT_EQ(0, status);
+    }
 
-  internal::Mutex mutex;
-  {
-    internal::MutexLock lock(&mutex);
-    pthread_attr_t  attr;
-    ASSERT_EQ(0, pthread_attr_init(&attr));
-    ASSERT_EQ(0, pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE));
-
-    const int status = pthread_create(&thread_id, &attr, &ThreadFunc, &mutex);
-    ASSERT_EQ(0, pthread_attr_destroy(&attr));
-    ASSERT_EQ(0, status);
-    EXPECT_EQ(starting_count + 1, GetThreadCount());
-  }
+    thread_count_after_create = GetThreadCount();
 
-  void* dummy;
-  ASSERT_EQ(0, pthread_join(thread_id, &dummy));
+    void* dummy;
+    ASSERT_EQ(0, pthread_join(thread_id, &dummy));
 
-  // The OS may not immediately report the updated thread count after
-  // joining a thread, causing flakiness in this test. To counter that, we
-  // wait for up to .5 seconds for the OS to report the correct value.
-  for (int i = 0; i < 5; ++i) {
-    if (GetThreadCount() == starting_count)
-      break;
+    // Join before we decide whether we need to retry the test. Retry if an
+    // arbitrary other thread was created or destroyed in the meantime.
+    if (thread_count_after_create != starting_count + 1) continue;
+
+    // The OS may not immediately report the updated thread count after
+    // joining a thread, causing flakiness in this test. To counter that, we
+    // wait for up to .5 seconds for the OS to report the correct value.
+    bool thread_count_matches = false;
+    for (int i = 0; i < 5; ++i) {
+      thread_count_after_join = GetThreadCount();
+      if (thread_count_after_join == starting_count) {
+        thread_count_matches = true;
+        break;
+      }
+
+      SleepMilliseconds(100);
+    }
+
+    // Retry if an arbitrary other thread was created or destroyed.
+    if (!thread_count_matches) continue;
 
-    SleepMilliseconds(100);
+    break;
   }
 
-  EXPECT_EQ(starting_count, GetThreadCount());
+  EXPECT_EQ(thread_count_after_create, starting_count + 1);
+  EXPECT_EQ(thread_count_after_join, starting_count);
 }
 #else
 TEST(GetThreadCountTest, ReturnsZeroWhenUnableToCountThreads) {