Clean up the area of pthread key destruction.
The previous commentary (based on code inspection) was wrong. We do correctly implement the POSIX semantics of only calling pthread key destructor functions for non-null values. This change updates the documentation to be correct, adds the missing unit tests that prove that the implementation is correct, and changes the implementation to make it more obviously correct (and so we can add an explicit code comment pointing out the relevant null check).
Change-Id: I04511021233da8aac80c010eb111ffe615171611
diff --git a/tests/pthread_test.cpp b/tests/pthread_test.cpp
index 5ce7d4d..680ef6e 100644
--- a/tests/pthread_test.cpp
+++ b/tests/pthread_test.cpp
@@ -59,6 +59,39 @@
ASSERT_EQ(EINVAL, pthread_key_delete(key));
}
+static std::vector<void*> example_key_destructor_data;
+static pthread_key_t example_key;
+static void example_key_destructor(void *data) {
+ // By the time the destructor function is running,
+ // this thread's value for the key should have been zeroed.
+ ASSERT_EQ(NULL, pthread_getspecific(example_key));
+
+ // Store the value so we can check we got the expected result.
+ example_key_destructor_data.push_back(data);
+}
+
+TEST(pthread, pthread_key_destructors) {
+ ASSERT_EQ(0, pthread_key_create(&example_key, example_key_destructor));
+
+ // Check that the destructor isn't called for a default null value.
+ std::thread([]() {}).join();
+ ASSERT_TRUE(example_key_destructor_data.empty());
+
+ // Check that the destructor isn't called for an explicit null value.
+ std::thread([]() {
+ ASSERT_EQ(0, pthread_setspecific(example_key, (void*) 1234));
+ ASSERT_EQ(0, pthread_setspecific(example_key, nullptr));
+ }).join();
+ ASSERT_TRUE(example_key_destructor_data.empty());
+
+ // Check that the destructor is called for a non-null value.
+ std::thread([]() { ASSERT_EQ(0, pthread_setspecific(example_key, (void*) 1234)); }).join();
+ ASSERT_EQ(1u, example_key_destructor_data.size());
+ ASSERT_EQ((void*) 1234, example_key_destructor_data[0]);
+
+ ASSERT_EQ(0, pthread_key_delete(example_key));
+}
+
TEST(pthread, pthread_keys_max) {
// POSIX says PTHREAD_KEYS_MAX should be at least _POSIX_THREAD_KEYS_MAX.
ASSERT_GE(PTHREAD_KEYS_MAX, _POSIX_THREAD_KEYS_MAX);