[Cython] cython-devel-tests-pyregr regression

[Vitja Makarov]

2012/8/23 Stefan Behnel <stefan_ml at behnel.de>:
> Vitja Makarov, 23.08.2012 07:03:
>> 2012/8/23 Stefan Behnel <stefan_ml at behnel.de>:
>>> Vitja Makarov, 22.08.2012 22:34:
>>>> 2012/8/23 Stefan Behnel:
>>>>> Vitja Makarov, 22.08.2012 22:11:
>>>>>> I've found regression:
>>>>>>
>>>>>> https://sage.math.washington.edu:8091/hudson/job/cython-devel-tests-pyregr/
>>>>>
>>>>> Interesting. It's a Py2 list comprehension in a class body that's failing here:
>>>>>
>>>>> """
>>>>>  class TestHelpSubparsersOrdering(HelpTestCase):
>>>>>      subparsers_signatures = [Sig(name=name)
>>>>>                               for name in ('a', 'b', 'c', 'd', 'e')]
>>>>>  """
>>>>>
>>>>> I wonder why "name" isn't declared as a variable yet at the point where it
>>>>> is being looked up in the function call.
>>>>
>>>>     def lookup_relative(self, name, pos):
>>>>         if name == "name":
>>>>             print name
>>>>             from ipdb import set_trace; set_trace()
>>>>         entry = self.lookup_here(name)
>>>>         if entry is not None and entry.pos[1:] <= pos[1:]: # Lookup fails here
>>>>             return entry
>>>>         if self.outer_scope:
>>>>             return self.outer_scope.lookup_relative(name, pos)
>>>>         return None
>>>>
>>>>
>>>> What is that comparison for?
>>>
>>> Ah, yes, it is wrong in this context. It was meant to prevent names defined
>>> further down in the class body from being considered assignments to the
>>> name being looked up. Class bodies are not function bodies, assignments in
>>> them do not make a name "local". As long as it's not assigned, it's not
>>> defined and must be looked up in the outer scope.
>>
>> Do you remember this ticket #671
>>
>> If there is assignment in the class body we first lookup in the class
>> dict and then in globals.
>>
>> B = 0
>> def foo():
>>     B = 1
>>     class Foo():
>>         A = B
>>         B = B
>>     class Bar():
>>         A = B
>>     print Foo.A, Foo.B, Bar.A
>> foo()
>>
>> prints "0 0 1"
>
> In the case at hand, it's not an assignment but a method declaration. Maybe
> that makes a difference.
>
> In any case, this needs some more investigation than I did for my change. I
> think it can be rolled back completely.
>
>
>>> I think comprehensions are actually the only case where a name is used in
>>> the source before its declaration. It should work in all other cases.
>>>
>>> I had considered solving this problem with the flow control analysis
>>> information, but I can't see how that helps me to figure out if an entry is
>>> already assigned (i.e. declared) at a given point in the class body.
>>>
>>> Any idea?
>>
>> What would you do with maybe assigned case?
>
> Hmm, yes - I guess we can't solve the general case at compile time. That's
> unfortunate, though, because it prevents proper compile time optimisation
> of builtins in class bodies when their names are assigned at some point,
> e.g. with a ".type()" method or ".set()", as was the case here.
>
> Stefan
>



This is NameNode related problem

The following code would fail as well:
XXX = 123
class Foo(object):
    t1 = XXX  # XXX   cf_is_null = True
    t2 = XXX  # XXX   cf_is_null = False
    XXX = 123

CF assumes that after first apperence of NULL name it must be then set
otherwise exception must be raised.
NameNode code relays on CF here, so I think it mustn't. We must
allways check result of PyObject_GetItem() and if's NULL look at the
globals then.

I'll try to fix it soon.


-- 
vitja.