### 23.9 Keeping track of available passes

When your plugin is loaded, you can inspect the various pass lists to determine what passes are available. However, other plugins might add new passes. Also, future changes to GCC might cause generic passes to be added after plugin loading. When a pass is first added to one of the pass lists, the event `PLUGIN_NEW_PASS` is invoked, with the callback parameter `gcc_data` pointing to the new pass.