[Python-Dev] [Python-checkins] cpython (3.2): don't use a slot wrapper from a different special method (closes #14658) (original) (raw)

Mark Shannon mark at hotpy.org
Tue Apr 24 17:26:14 CEST 2012

I'm not happy with this fix.

Admittedly code like:

class S(str): getattr = str.add s = S('a') print(S.b)

is a little weird. But I think it should work (ie print 'ab') properly.

This works without the patch.

class S(str): getattribute = str.add s = S('a') print(S.b)

(Prints 'ab')

Also "slot wrapper" is a low-level implementation detail and shouldn't impact the language semantics.

dict.getitem is a slot wrapper; dict.getitem is not. str.getitem is a slot wrapper; list.getitem is not. If any of these change then the semantics of the language changes.

Cheers, Mark

benjamin.peterson wrote:

http://hg.python.org/cpython/rev/971865f12377 changeset: 76518:971865f12377 branch: 3.2 parent: 76506:f7b002e5cac7 user: Benjamin Peterson <benjamin at python.org> date: Tue Apr 24 11:06:25 2012 -0400 summary: don't use a slot wrapper from a different special method (closes #14658)

This also alters the fix to #11603. Specifically, setting repr to object.str now raises a recursion RuntimeError when str() or repr() is called instead of silently bypassing the recursion. I believe this behavior is more correct. files: Lib/test/testdescr.py | 10 +++++++++- Misc/NEWS | 6 ++++++ Objects/typeobject.c | 5 +++-- 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/Lib/test/testdescr.py b/Lib/test/testdescr.py --- a/Lib/test/testdescr.py +++ b/Lib/test/testdescr.py @@ -4430,7 +4430,15 @@ pass Foo.repr = Foo.str foo = Foo() - str(foo) + self.assertRaises(RuntimeError, str, foo) + self.assertRaises(RuntimeError, repr, foo) + + def testmixingslotwrappers(self): + class X(dict): + setattr = dict.setitem + x = X() + x.y = 42 + self.assertEqual(x["y"], 42) def testcyclethroughdict(self): # See bug #1469629 diff --git a/Misc/NEWS b/Misc/NEWS --- a/Misc/NEWS +++ b/Misc/NEWS @@ -10,6 +10,12 @@ Core and Builtins ----------------- +- Issue #11603 (again): Setting repr to str now raises a RuntimeError + when repr() or str() is called on such an object. + +- Issue #14658: Fix binding a special method to a builtin implementation of a + special method with a different name. + - Issue #14630: Fix a memory access bug for instances of a subclass of int with value 0. diff --git a/Objects/typeobject.c b/Objects/typeobject.c --- a/Objects/typeobject.c +++ b/Objects/typeobject.c @@ -2928,7 +2928,7 @@ unaryfunc f; f = PyTYPE(self)->tprepr; - if (f == NULL || f == objectstr) + if (f == NULL) f = objectrepr; return f(self); } @@ -5757,7 +5757,8 @@ } continue; } - if (PyTYPE(descr) == &PyWrapperDescrType) { + if (PyTYPE(descr) == &PyWrapperDescrType && + ((PyWrapperDescrObject *)descr)->dbase->namestrobj == p->namestrobj) { void **tptr = resolveslotdups(type, p->namestrobj); if (tptr == NULL || tptr == ptr) generic = p->function;

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