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SF bug 839548: Bug in type's GC handling causes segfaults.

Browse source 
Also SF patch 843455.

This is a critical bugfix.
I'll backport to 2.3 maint, but not beyond that.  The bugs this fixes
have been there since weakrefs were introduced.
This commit is contained in:
Tim Peters 2003-11-20 21:21:46 +00:00
parent 901dc98316
commit 403a203223
6 changed files with 491 additions and 20 deletions
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34
Objects/weakrefobject.c
View file

@ -53,17 +53,43 @@ clear_weakref(PyWeakReference *self)
if (*list == self)
*list = self->wr_next;
self->wr_object = Py_None;
self->wr_callback = NULL;
if (self->wr_prev != NULL)
self->wr_prev->wr_next = self->wr_next;
if (self->wr_next != NULL)
self->wr_next->wr_prev = self->wr_prev;
self->wr_prev = NULL;
self->wr_next = NULL;
Py_XDECREF(callback);
}
if (callback != NULL) {
Py_DECREF(callback);
self->wr_callback = NULL;
}
}
/* Cyclic gc uses this to *just* clear the passed-in reference, leaving
* the callback intact and uncalled. It must be possible to call self's
* tp_dealloc() after calling this, so self has to be left in a sane enough
* state for that to work. We expect tp_dealloc to decref the callback
* then. The reason for not letting clear_weakref() decref the callback
* right now is that if the callback goes away, that may in turn trigger
* another callback (if a weak reference to the callback exists) -- running
* arbitrary Python code in the middle of gc is a disaster. The convolution
* here allows gc to delay triggering such callbacks until the world is in
* a sane state again.
*/
void
_PyWeakref_ClearRef(PyWeakReference *self)
{
PyObject *callback;
assert(self != NULL);
assert(PyWeakref_Check(self));
/* Preserve and restore the callback around clear_weakref. */
callback = self->wr_callback;
self->wr_callback = NULL;
clear_weakref(self);
self->wr_callback = callback;
}
static void
weakref_dealloc(PyWeakReference *self)
@ -117,7 +143,7 @@ weakref_hash(PyWeakReference *self)
self->hash = PyObject_Hash(PyWeakref_GET_OBJECT(self));
return self->hash;
}
static PyObject *
weakref_repr(PyWeakReference *self)
@ -324,7 +350,7 @@ WRAP_BINARY(proxy_iand, PyNumber_InPlaceAnd)
WRAP_BINARY(proxy_ixor, PyNumber_InPlaceXor)
WRAP_BINARY(proxy_ior, PyNumber_InPlaceOr)
static int
static int
proxy_nonzero(PyWeakReference *proxy)
{
PyObject *o = PyWeakref_GET_OBJECT(proxy);