As far as I can tell you are forced by the code watcher API to use global vars. The callbacks take raw C pointers, and they don’t carry a void* user data parameter. Is there a trick to this? Or a reason the standard user void* pattern for C callbacks isn’t used? IIUC this would prevent being able to reload a module using the API, since you will end up with two module objects but only one global.
/*
* A callback that is invoked for different events in a code object's lifecycle.
*
* The callback is invoked with a borrowed reference to co, after it is
* created and before it is destroyed.
*
* If the callback sets an exception, it must return -1. Otherwise
* it should return 0.
*/
typedef int (*PyCode_WatchCallback)(
PyCodeEvent event,
PyCodeObject* co);
/*
* Register a per-interpreter callback that will be invoked for code object
* lifecycle events.
*
* Returns a handle that may be passed to PyCode_ClearWatcher on success,
* or -1 and sets an error if no more handles are available.
*/
PyAPI_FUNC(int) PyCode_AddWatcher(PyCode_WatchCallback callback);