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List:       pykde
Subject:    Re: [PyQt] Crash in siplib.c:findSlot, with test case and fix
From:       Phil Thompson <phil () riverbankcomputing ! com>
Date:       2009-04-24 17:31:09
Message-ID: efb9b9f1a36ec35a31d3d31cb576b040 () localhost
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On Thu, 23 Apr 2009 15:21:51 -0700, Matt Newell <newellm@blur.com> wrote:
> On Thursday 23 April 2009 10:32:59 Matt Newell wrote:
>> It seems if a wrapped class A has slots and a wrapped subclass B does
not
>> then an assert is triggered when calling a slot from A on an instance of
>> B.
>>
>> To build and run the test --
>>
>> ./build.sh
>> python test.py
>>
>>
>> findSlot function that fixes all problems for me
>>
>> static void *findSlot(PyObject *self, sipPySlotType st)
>> {
>>     sipPySlotDef *psd;
>>     PyTypeObject *py_type = Py_TYPE(self);
>>
>> 	if( PySequence_Check( py_type->tp_bases ) ) {
>> 		int i = 0, end = PySequence_Size( py_type->tp_mro );
>> 		for( ; i < end; i++ ) {
>> 			PyObject * type_o = PySequence_GetItem( py_type->tp_mro, i );
>> 			if( PyType_Check(type_o) ) {
>> 				PyTypeObject * py_type_to_check = (PyTypeObject*)type_o;
>>
>> 				/* If it is not a wrapper then it must be an enum. */
>> 				if (PyObject_TypeCheck((PyObject *)py_type_to_check,
>> &sipWrapperType_Type))
>> 					psd = ((sipClassTypeDef *)((sipWrapperType *)
>> (py_type_to_check))->type)->ctd_pyslots;
>> 				else
>> 				{
>> 					assert(PyObject_TypeCheck((PyObject *)py_type_to_check,
>> &sipEnumType_Type));
>>
>> 					psd = ((sipEnumTypeDef *)((sipEnumTypeObject *)
>> (py_type_to_check))->type)->etd_pyslots;
>> 				}
>> 				while (psd && psd->psd_func != NULL)
>> 				{
>> 					if (psd->psd_type == st)
>> 						return psd->psd_func;
>>
>> 					++psd;
>> 				}
>> 			} else
>> 				printf( "mro member not a type object\n" );
>> 		}
>> 	}
>>
>>     assert(NULL);
>>
>>     /* This should never happen. */
>>     return NULL;
>> }
> 
> 
> 
> My "fix" fixes the test case but causes a crash with
> QTreeWidgeItem() == None
> 
> so it's obviously not a solution.

It is the right solution - though I've implemented it differently.

> Calling QTreeWidgetItem() == None without my change it ends up returning
> NULL 
> from findSlot which the comment indicates should never happen.

The comment was wrong so later code needed to handle that case.

Hopefully it's all fixed in tonight's snapshot.

Thanks,
Phil
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