This code causes segfault.

class Foo: pass
foo = Foo()
1 in foo

E:\python-dev>py a.py
Exception exceptions.TypeError: "argument of type
'instance' is not iterable" in
 'garbage collection' ignored
Fatal Python error: unexpected exception during garbage
collection

This bug seems to be introduced by revision 45644
change for Objects/classobject.c
# -1 (error) is converted to 0 (False)

I think this can be fixed by attached patch. Thank you.

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Attaching to Martin since the mentioned revision is his.

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I fixed the problem slightly differently without casting,
but rather checking the result.  The patch also contains a
test case.

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I agree with Neal's patch, committed as r52662 and r52663.

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Sorry for posting to closed entry, but this is related...

Maybe similar patch is apropriate for PySequence_Contains in
Objects/abstract.c like this? Thank you.

Index: Objects/abstract.c
===================================================================
--- Objects/abstract.c	(revision 52664)
+++ Objects/abstract.c	(working copy)
@@ -1719,7 +1719,9 @@
 			return (*sqm->sq_contains)(seq, ob);
 	}
 	result = _PySequence_IterSearch(seq, ob,
PY_ITERSEARCH_CONTAINS);
-	return Py_SAFE_DOWNCAST(result, Py_ssize_t, int);
+	if (result >= 0)
+	    return result > 0;
+	return -1;
 }
 
 /* Backwards compatibility */

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It's not strictly necessary, IMO: PY_ITERSEARCH_CONTAINS is
guaranteed to return -1, 0, 1, just as PySequence_Contains
should. So the safe downcast is correct.

IOW, your patch would have been correct, as well. I liked
Neal's patch more, because it combines the error cases into
a single return, and because it had a test case.