Author larry
Recipients ajaksu2, dalcinl, larry
Date 2009-04-06.07:58:33
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Message-id <1239004724.72.0.435051266708.issue5630@psf.upfronthosting.co.za>
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I discussed this off-list with GvR.  He was primarily concerned with
fixing the passing-around-a-vtable C API usage of CObject, but he wanted
to preserve as much backwards compatibility as possible.  In the end, he
suggested I create a new API and leave CObject unchanged.  I've done
that, incorporating many of GvR's suggestions, though the blame for the
proposed new API is ultimately mine.

The new object is called a "Capsule".  (I *had* wanted to call it
"Wrapper", but there's already a PyWrapper_New in descrobject.h.) 
Highlights of the new API:
* PyCapsule_New() replaces PyCObject_FromVoidPtr.
  * It takes a void * pointer, a const char *name, and a destructor.
  * The pointer must not be NULL.
  * The name may be NULL; if it is not NULL, it must be a valid C string
which outlives the capsule.
  * The destructor takes a PyObject *, not a void *.
* PyCapsule_GetPointer() replaces PyCObject_AsVoidPtr.
  * It takes a PyObject * and a const char *name.
  * The name must compare to the name inside the object; either they're
both NULL or they strcmp to be the same.
* PyCapsule_Import() replaces PyCObject_Import.
  * It takes three arguments: const char *module_name, const char
*attribute_name, int no_block.
  * It ensures that the "name" of the Capsule is "modulename.attributename".
  * If no_block is true, it uses PyModule_ImportModuleNoBlock.
* The PyCapsule structure is private.  There are accessors for all
fields: pointer, name, destructor, and "context"
  * The "context" is a second "void *" you can set / get.

I've attached a patch to implement this; it was written against svn
r71304.  The patch isn't ready to be applied--there is no documentation
for the new API beyond the header file.

GvR and I disagree on one point: he thinks that we should leave CObject
in forever, undeprecated.  I think we should deprecate it now and remove
it... whenever we'd do that.  The new API does everything the old one
does, and more, and it's cleaner and safer.
History
Date User Action Args
2009-04-06 07:58:45larrysetrecipients: + larry, dalcinl, ajaksu2
2009-04-06 07:58:44larrysetmessageid: <1239004724.72.0.435051266708.issue5630@psf.upfronthosting.co.za>
2009-04-06 07:58:43larrylinkissue5630 messages
2009-04-06 07:58:42larrycreate