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bpo-33622: Fix issues with handling errors in the GC. (GH-7078) 

* Fixed a leak when the GC fails to add an object with __del__ into
  the gc.garbage list.
* PyGC_Collect() can now be called when an exception is set and
  preserves it.
* Fixed an undefined behavior with comparing a dead pointer with NULL.
(cherry picked from commit 301e3cc8a5)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
This commit is contained in:
Miss Islington (bot) 2018-05-24 05:39:08 -07:00 committed by GitHub
parent b2ab5dc72b
commit 2fe940c727
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2 changed files with 15 additions and 8 deletions
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4
Misc/NEWS.d/next/Core and Builtins/2018-05-23-20-46-14.bpo-33622.xPucO9.rst Normal file
View File

@ -0,0 +1,4 @@
Fixed a leak when the garbage collector fails to add an object with the
``__del__`` method or referenced by it into the :data:`gc.garbage` list.
:c:func:`PyGC_Collect` can now be called when an exception is set and
preserves it.

19
Modules/gcmodule.c
View File

@ -648,10 +648,8 @@ debug_cycle(const char *msg, PyObject *op)
* garbage list (a Python list), else only the objects in finalizers with
* __del__ methods are appended to garbage. All objects in finalizers are
* merged into the old list regardless.
* Returns 0 if all OK, <0 on error (out of memory to grow the garbage list).
* The finalizers list is made empty on a successful return.
*/
static int
static void
handle_legacy_finalizers(PyGC_Head *finalizers, PyGC_Head *old)
{
PyGC_Head *gc = finalizers->gc.gc_next;
@ -666,12 +664,11 @@ handle_legacy_finalizers(PyGC_Head *finalizers, PyGC_Head *old)
if ((_PyRuntime.gc.debug & DEBUG_SAVEALL) || has_legacy_finalizer(op)) {
if (PyList_Append(_PyRuntime.gc.garbage, op) < 0)
return -1;
break;
}
}
gc_list_merge(finalizers, old);
return 0;
}
/* Run first-time finalizers (if any) on all the objects in collectable.
@ -945,7 +942,7 @@ collect(int generation, Py_ssize_t *n_collected, Py_ssize_t *n_uncollectable,
* reachable list of garbage. The programmer has to deal with
* this if they insist on creating this type of structure.
*/
(void)handle_legacy_finalizers(&finalizers, old);
handle_legacy_finalizers(&finalizers, old);
/* Clear free list only during the collection of the highest
* generation */
@ -1009,9 +1006,12 @@ invoke_gc_callback(const char *phase, int generation,
PyObject *r, *cb = PyList_GET_ITEM(_PyRuntime.gc.callbacks, i);
Py_INCREF(cb); /* make sure cb doesn't go away */
r = PyObject_CallFunction(cb, "sO", phase, info);
Py_XDECREF(r);
if (r == NULL)
if (r == NULL) {
PyErr_WriteUnraisable(cb);
}
else {
Py_DECREF(r);
}
Py_DECREF(cb);
}
Py_XDECREF(info);
@ -1567,8 +1567,11 @@ PyGC_Collect(void)
if (_PyRuntime.gc.collecting)
n = 0; /* already collecting, don't do anything */
else {
PyObject *exc, *value, *tb;
_PyRuntime.gc.collecting = 1;
PyErr_Fetch(&exc, &value, &tb);
n = collect_with_callback(NUM_GENERATIONS - 1);
PyErr_Restore(exc, value, tb);
_PyRuntime.gc.collecting = 0;
}