Add null checks in Messaging task completions (#1602)

* Add null checks in Messaging task completions

* Add mutex and update readme

* Update messaging.cc

Author: a-maurice

messaging/src/android/cpp/messaging.cc

@@ -124,6 +124,9 @@ static std::string* g_lockfile_path;
 
 static Mutex* g_file_locker_mutex;
 
+// Mutex for managing if FutureData is safe to use, or if it has been deleted.
+static Mutex g_future_data_mutex;
+
 static const char* kMessagingNotInitializedError = "Messaging not initialized.";
 
 static void HandlePendingSubscriptions();
@@ -706,7 +709,10 @@ void Terminate() {
   SetListener(nullptr);
   ReleaseClasses(env);
   util::Terminate(env);
-  FutureData::Destroy();
+  {
+    MutexLock lock(g_future_data_mutex);
+    FutureData::Destroy();
+  }
 }
 
 // Start a service which will communicate with the Firebase Cloud Messaging
@@ -826,8 +832,13 @@ static void CompleteVoidCallback(JNIEnv* env, jobject result,
   FutureHandle handle(future_id);
   Error error =
       (result_code == util::kFutureResultSuccess) ? kErrorNone : kErrorUnknown;
-  ReferenceCountedFutureImpl* api = FutureData::Get()->api();
-  api->Complete(handle, error, status_message);
+  MutexLock lock(g_future_data_mutex);
+  if (FutureData::Get() && FutureData::Get()->api()) {
+    ReferenceCountedFutureImpl* api = FutureData::Get()->api();
+    api->Complete(handle, error, status_message);
+  } else {
+    LogWarning("Failed to complete Future as it was likely already deleted.");
+  }
   if (result) env->DeleteLocalRef(result);
 }
 
@@ -843,8 +854,13 @@ static void CompleteStringCallback(JNIEnv* env, jobject result,
   SafeFutureHandle<std::string>* handle =
       reinterpret_cast<SafeFutureHandle<std::string>*>(callback_data);
   Error error = success ? kErrorNone : kErrorUnknown;
-  ReferenceCountedFutureImpl* api = FutureData::Get()->api();
-  api->CompleteWithResult(*handle, error, status_message, result_value);
+  MutexLock lock(g_future_data_mutex);
+  if (FutureData::Get() && FutureData::Get()->api()) {
+    ReferenceCountedFutureImpl* api = FutureData::Get()->api();
+    api->CompleteWithResult(*handle, error, status_message, result_value);
+  } else {
+    LogWarning("Failed to complete Future as it was likely already deleted.");
+  }
   delete handle;
 }
 

release_build_files/readme.md

@@ -634,8 +634,10 @@ code.
 ### Upcoming Release
 -   Changes
     - Analytics (iOS): Add support for
-    `InitiateOnDeviceConversionMeasurementWithHashedEmailAddress` and
-    `InitiateOnDeviceConversionMeasurementWithHashedPhoneNumber`.
+      `InitiateOnDeviceConversionMeasurementWithHashedEmailAddress` and
+      `InitiateOnDeviceConversionMeasurementWithHashedPhoneNumber`.
+    - Messaging (Android): Addressed potential race condition on receiving
+      messages after cleanup.
 
 ### 12.0.0
 -   Changes