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?