Handle leak of message handle when no engine present

Author: robert-ancell

shell/platform/linux/fl_binary_messenger.cc

@@ -59,6 +59,9 @@ static void response_handle_free(FlBinaryMessengerResponseHandle* handle) {
   g_free(handle);
 }
 
+G_DEFINE_AUTOPTR_CLEANUP_FUNC(FlBinaryMessengerResponseHandle,
+                              response_handle_free);
+
 static void engine_weak_notify_cb(gpointer user_data, GObject* object) {
   FlBinaryMessenger* self = FL_BINARY_MESSENGER(user_data);
   self->engine = nullptr;
@@ -145,12 +148,15 @@ G_MODULE_EXPORT gboolean fl_binary_messenger_send_response(
   g_return_val_if_fail(FL_IS_BINARY_MESSENGER(self), FALSE);
   g_return_val_if_fail(response_handle != nullptr, FALSE);
 
+  // Take reference to ensure it is freed
+  g_autoptr(FlBinaryMessengerResponseHandle) owned_response_handle =
+      response_handle;
+
   if (self->engine == nullptr)
     return TRUE;
 
   gboolean result = fl_engine_send_platform_message_response(
-      self->engine, response_handle->response_handle, response, error);
-  response_handle_free(response_handle);
+      self->engine, owned_response_handle->response_handle, response, error);
 
   return result;
 }

shell/platform/linux/public/flutter_linux/fl_binary_messenger.h

@@ -39,7 +39,7 @@ typedef struct _FlBinaryMessengerResponseHandle FlBinaryMessengerResponseHandle;
  * @messenger: a #FlBinaryMessenger
  * @channel: channel message received on
  * @message: message content received from Dart
- * @response_handle: a handle to respond to the message with
+ * @response_handle: (transfer full): a handle to respond to the message with
  * @user_data: (closure): data provided when registering this callback
  *
  * Function called when platform messages are received. The receiver must
@@ -74,7 +74,8 @@ void fl_binary_messenger_set_message_handler_on_channel(
 /**
  * fl_binary_messenger_send_response:
  * @binary_messenger: a #FlBinaryMessenger
- * @response_handle: handle that was provided in a #FlBinaryMessengerCallback
+ * @response_handle: (transfer full): handle that was provided in a
+ * #FlBinaryMessengerCallback
  * @response: (allow-none): response to send or %NULL for an empty response
  * @error: (allow-none): #GError location to store the error occurring, or %NULL
  * to ignore