How do you propose to use `mark` and `gc` of the `fe_Handlers` structure?

[ooichu]

The FE_TPTR has no extra data to recognize how this should be marked (with fe_handlers(ctx)->mark) or released (with fe_handlers(ctx)->gc). In most cases, you need to change the data structure of data in ptr to recognize it from handlers. Why not add handlers directly to the FE_TPTR type?