The default PMC, to which most PMCs delegate their unhandled vtables, makes some odd choices in terms of what functionality it attempts to provide versus giving up and throwing a "not implemented" exception. Among the "implemented" vtables are get_pointer, freeze, thaw, visit, and clone. default's implementation of these isn't particularly helpful, and IMHO, actively hinders by hiding the fact that many PMCs do not meaningfully implement these interfaces.
For example, what does Integer.get_pointer() do? If you guessed something along the lines of "gets a pointer to the INTVAL backing the PMC", you'd be dead wrong. default helpfully tries to implement the vtable, but fails miserably, since it lacks sufficient information to provide the "obvious" choice for the implementation. I would like to remove these vtables from default (which would cause pmc2c to default them to throwing "vtable not implemented" exceptions). This has the very real potential to break code which makes use of these interfaces on PMCs which don't meaningfully implement them (for example, we have some tests which call get_pointer() an values that don't really implement get_pointer). I would argue that such code already has a subtle bug which is made more obvious by this change. For example, removing default.get_pointer() breaks nqp-nom (well really, the get_addr_i_p opcode nqp uses, whose two senses need disentangling). I intend to fix the underlying issues to this and any other reported issues before these changes hit master. For the purpose of experimentation, I have put the kill-useless-defaults branch up on github. _______________________________________________ http://lists.parrot.org/mailman/listinfo/parrot-dev
