Fix Memory Leak Caused By Wrong Limited API Default

When a type has nullptr as tp_dealloc, there apply different defaults.

Static types had object_dealloc as default, while new heaptypes
created with type_new have subtype_dealloc as default.

A problem was now that PyType_FromSpec also has
subtype_dealloc as default. But that is wrong, because a type that
was written with the static type approach is already written with
object_dealloc in mind and takes somehow care about further issues
with that type.

When we now convert this type and suddenly use subtype_dealloc
instead of object_dealloc, things get pretty wrong.

Finding that out was pretty hard and took quite long to understand.

The fix was then very easy and is the best proof:
Replacing our former (wrong) solution of supplying an
SbkDummyDealloc with a function object_dealloc works perfectly,
and the leakage completely vanished.

The documentation now is also corrected.

Task-number: PYSIDE-832
Change-Id: Ifc20c28172eb5663cd5e60dac52e0a43acfb626c
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

1 files changed, 4 insertions, 2 deletions

diff --git a/sources/shiboken2/libshiboken/basewrapper.cpp b/sources/shiboken2/libshiboken/basewrapper.cpp
index 0aba26679..5ca4172c8 100644
--- a/sources/shiboken2/libshiboken/basewrapper.cpp
+++ b/sources/shiboken2/libshiboken/basewrapper.cpp
@@ -416,8 +416,10 @@ PyObject* SbkQAppTpNew(PyTypeObject* subtype, PyObject *, PyObject *)
 }
 
 void
-SbkDummyDealloc(PyObject *)
-{}
+object_dealloc(PyObject *self)
+{
+    Py_TYPE(self)->tp_free(self);
+}
 
 PyObject *
 SbkDummyNew(PyTypeObject *type, PyObject*, PyObject*)