wait_for may return before callback

The problem is similar with CPP-514. A unit test is appended in the end.
Maybe it's difficult to guarantee threads waiting for a future see the side effects of the callback
because currently one may call future::wait_for in a callback without deadlocks.

+
+enum class callback_status {
+ WAIT_CALL,
+ CALLING,
+ CALLED,
+};
+
+void on_future_long_callback(CassFuture* future, void* data) {
+ callback_status* callback_status = static_cast<enum callback_status*>(data);
+ *callback_status = callback_status::CALLING;
+ test::Utils::msleep(DELAY_MS);
+ *callback_status = callback_status::CALLED;
+}
+
+TEST(FutureUnitTest, WaitForReturnsAfterCallback) {
+ Future future(Future::FUTURE_TYPE_GENERIC);
+ callback_status status(callback_status::WAIT_CALL);
+ ASSERT_TRUE(future.set_callback(&on_future_long_callback, &status));
+
+ uv_thread_t thread;
+ ASSERT_EQ(0, uv_thread_create(&thread, start_timer, &future));
+
+ while ((volatile callback_status)&status == callback_status::WAIT_CALL) {
+ }
+
+ ASSERT_EQ(status, callback_status::CALLING);
+ ASSERT_FALSE(future.wait_for(1e+7)); // 10 millisecond
+ ASSERT_FALSE(future.ready());
+ ASSERT_NE(status, callback_status::CALLED);
+
+ ASSERT_TRUE(future.wait_for(1e+9)); // 1 second
+ ASSERT_TRUE(future.ready());
+ ASSERT_EQ(status, callback_status::CALLED);
+
+ ASSERT_EQ(0, uv_thread_join(&thread));
+}