[Python-Dev] Need advice, maybe support (original) (raw)

Guido van Rossum guido@python.org
Tue, 20 May 2003 15:30:56 -0400

There is one second thought about this, but I'm not sure whether it is allowed to do so:

Assuming that I would simply do add a field to PyMethodDef, and take care that all types coming from foreign binaries don't have that special type bit set, could I not simply create a new method table and replace it for that external type by just changing its method table pointer?

Probably.

I just realize that there are two uses of PyMethodDef.

One is the "classic", where the type's tp_getattr[o] implementation calls Py_FindMethod. The other is the new style where the PyMethodDef array is in tp_methods, and is scanned once by PyType_Ready. 3rd party modules that have been around for a while are likely to use Py_FindMethod. With Py_FindMethod you don't have a convenient way to store the pointer to the converted table, so it may be better to simply check your bit in the first array element and then cast to a PyMethodDef or a PyMethodDefEx array based on what the bit says (you can safely assume that all elements of an array are the same size :-).

I think traversing method tables is always an action that the core dll does. Or do I have to fear that an extension does special things to method tables at runtime?

I wouldn't lose sleep over that.

If that approach is trustworthy, I also could drop the request for these 8 bits.

Sure. Ah, a bit in the type would work just as well, and Py_FindMethod does have access to the type.

--Guido van Rossum (home page: http://www.python.org/~guido/)