On Tue, Mar 31, 2009 at 20:34, Guido van Rossum <gu...@python.org> wrote:
> Can you get Jim Fulton's feedback? ISTR he originated this. > I thought Neal started this idea? -Brett > > On Tue, Mar 31, 2009 at 12:14 PM, Larry Hastings <la...@hastings.org> > wrote: > > > > The CObject API has two flaws. > > > > First, there is no usable type safety mechanism. You can store a void > > *object, and a void *description. There is no established schema for > > the description; it could be an integer cast to a pointer, or it could > > point to memory of any configuration, or it could be NULL. Thus users > > of the CObject API generally ignore it--thus working without any type > > safety whatsoever. A programmer could crash the interpreter from pure > > Python by mixing and matching CObjects from different modules (e.g. give > > "curses" a CObject from "_ctypes"). > > > > Second, the destructor callback is defined as taking *either* one *or* > > two parameters, depending on whether the "descr" pointer is non-NULL. One > > can debate the finer points of what is and isn't defined behavior in > > C, but at its heart this is a sloppy API. > > > > MvL and I discussed this last night and decided to float a revision of > > the API. I wrote the patch, though, so don't blame Martin if you don't > > like my specific approach. > > > > The color of this particular bike shed is: > > * The PyCObject is now a private data structure; you must use accessors. > > I added accessors for all the members. > > * The constructors and the main accessor (PyCObject_AsVoidPtr) now all > > *require* a "const char *type" parameter, which must be a non-NULL C > > string of non-zero length. If you call that accessor and the "type" > > is invalid *or doesn't match*, it fails. > > * The destructor now takes the PyObject *, not the PyCObject *. You > > must use accessors to get your hands on the data inside to free it. > > > > Yes, you can easily skip around the "matching type" restriction by > > calling PyCObject_AsVoidPtr(cobj, PyCObject_GetType(cobj)). The point > > of my API changes is to *encourage* correct use. > > > > I've posted a patch implementing this change in the 3.1 trunk to the > > bug tracker: > > > > http://bugs.python.org/issue5630 > > > > I look forward to your comments! > > > > > > /larry/ > > > > _______________________________________________ > > Python-Dev mailing list > > Python-Dev@python.org > > http://mail.python.org/mailman/listinfo/python-dev > > Unsubscribe: > > http://mail.python.org/mailman/options/python-dev/guido%40python.org > > > > > > -- > --Guido van Rossum (home page: > http://www.python.org/~guido/<http://www.python.org/%7Eguido/> > ) > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > http://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > http://mail.python.org/mailman/options/python-dev/brett%40python.org >
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