Re: [Pyobjc-dev] Handling (void *)

[Ronald O. <ous...@ci...>]

On Friday, Nov 8, 2002, at 10:59 Europe/Amsterdam, Peter Montagner 
wrote:
> So you think that we should treat (void*) as an integer rather than a 
> pointer, right? That works for me but it does seem a bit inelegant.
At least for now and only for specific methods. It is not very elegant, 
but at least it allows you to use a number of APIs that are off-limits 
at the moment.

BTW. I did not propose to treat all void* as integers, that would make 
it impossible to use some other APIs.

>
> Is there anything in python (2.2 onwards of course) that isn't an 
> object? If not, I think we should consider (void *) to be synonymous 
> with (id). The other use for (void*), as a pointer to block of memory 
> (eg. write()), can't really be done in python without wrapping it in 
> an object, right? So any API using (void *) for that purpose would 
> need to be specially wrapped anyway. Am I wrong?
Everything in python is an object from at Python 1.0, and probably 
right from the start. This doesn't mean we can just go on and use 
python objects for the userInfo argument, because of reference 
counting: Because the invoked method doesn't know we actually pas in a 
PyObject* or id, it doesn't know that it should increase the refcount. 
This means that the object may be garbage collected before it is passed 
back to us, unless we make sure a reference to it stays alive for as 
long as needed. I'd prefer not to introduce ways to easily memory 
corruption bugs in Python programs ;-).

BTW. Jack's solution (None->nil, PyCObject->extract the pointer, ...) 
is a better solution for almost anything with the possible exception of 
the userInfo arguments in some Cocoa APIs. This does work correctly 
with 'void*-as-pointer-to-block-of-memory'.

BTW2. A python object is _not_ an objective-C object, the pyobjc module 
just hides the differences. In some instances the difference is 
important, mostly when Objective-C code doesn't play by the rules (see 
the iClass example for an example of this)

Ronald