[Python-Dev] another Py_TPFLAGS_HEAPTYPE question (original) (raw)

Joshua Haberman joshua at reverberate.org
Mon Aug 17 00:08:55 CEST 2009

I wrote to this list a few weeks ago asking about Py_TPFLAGS_HEAPTYPE (http://thread.gmane.org/gmane.comp.python.devel/105648). It occurred to me today that I could probably make object instances INCREF and DECREF my type appropriately, without setting Py_TPFLAGS_HEAPTYPE, by writing my own tp_alloc and tp_dealloc functions. My tp_alloc function could be:

PyObject *my_tp_alloc(PyTypeObject *type, Py_ssize_t nitems) { PyObject *obj = PyType_GenericAlloc(type, nitems); if(obj) Py_INCREF(type); return obj; }

This seems right since it is PyType_GenericAlloc that contains this excerpt:

if (type->tp_flags & Py_TPFLAGS_HEAPTYPE) Py_INCREF(type);

I don't want to set Py_TPFLAGS_HEAPTYPE, but I want to get that Py_INCREF(), so far so good.

But I couldn't find the corresponding Py_DECREF() in typeobject.c to the above Py_INCREF(). Notably, object_dealloc() does not call Py_DECREF(self->ob_type) if self->ob_type has the Py_TPFLAGS_HEAPTYPE flag set.

So where does the Py_DECREF() for the above Py_INCREF() live? I expected to find this code snippet somewhere, but couldn't:

if (type->tp_flags & Py_TPFLAGS_HEAPTYPE) Py_DECREF(type);

Josh

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