Using alternative PyObject* in dynamically created classes

[Thomas Heller]

Jacek Generowicz <jacek.generowicz at cern.ch> writes:

> Jacek Generowicz <jacek.generowicz at cern.ch> writes:
>
>> I would like some of my _dynamically_ created new-style classes to
>> have instances which are not represented by the standard PyObject, but
>> one which has an extra void* slot which I want to use for my nefarious
>> purposes, in extension functions. The pointer need not be initialized
>> (for now) I just want it to be there in case I want to stuff something
>> in there later on in the run.
>> 
>> What is the laziest way of achieving this?
>> 
>> As far as I can tell, PyTypeObject (and its allocators, deallocators,
>> methods in general) only refer to the type of the instance struct via
>> tp_basicsize (where only the struct's size is held). 
>> 
>> So my first attempt merely resets tp_basicsize to the size of my
>> alternative instance struct, as soon as the class is created. This
>> goes horribly wrong when instances of the class are deallocated, but I
>> can't see why.
>> 
>> Where else must I provide information about the instance struct type ?
>> 
>> 
>> [I will be away for a few days, from a few hours from now; please
>> don't take a long response time as a sign of rudeness.]
>
>
> Hmm ... no takers ?
>
> :-(

Can't you simply create a new, subclassable Python type with an
additonal void* slot, and derive your classes from it?  Where's the
problem?

Thomas