Author: Armin Rigo <[email protected]>
Branch: extradoc
Changeset: r5759:011142ec6be4
Date: 2016-12-05 09:05 +0100
http://bitbucket.org/pypy/extradoc/changeset/011142ec6be4/
Log: add
diff --git a/planning/py3.5/cpython-crashers.rst
b/planning/py3.5/cpython-crashers.rst
--- a/planning/py3.5/cpython-crashers.rst
+++ b/planning/py3.5/cpython-crashers.rst
@@ -64,6 +64,21 @@
f()
sys.settrace(None)
+* I didn't try, but it seems that typeobject.c:mro_internal() is prone
+ to a refcount crash. It does this::
+
+ old_mro = type->tp_mro;
+ ...mro_invoke()... /* might cause reentrance */
+ type->tp_mro = new_mro;
+ ...
+ Py_XDECREF(old_mro);
+
+ This last XDECREF drops the reference held by the previous value of
+ ``type->tp_mro`` after we changed it. But ``type->tp_mro`` might have
+ changed because of mro_invoke(), which calls pure Python code. If it
+ did change, then old_mro is no longer the old value of
+ ``type->tp_mro``. The wrong object gets decrefed.
+
Non-segfaulting bugs
--------------------
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