On Fri, May 21, 2010 at 1:26 AM, Lisandro Dalcin <[email protected]> wrote:
> On 20 May 2010 13:54, Haoyu Bai <[email protected]> wrote:
>> Hi,
>>
>> While I get the the nonlocal keyword implemented, now the inner
>> function is able to write to the closure. This cause refnanny lost
>> tracking on the closure variables when following the refcounting rules
>> described at http://wiki.cython.org/refcounting . For example:
>>
>> def foo():
>> x=0 # INCREF(0), 0 get traced by refnanny
>> def bar():
>> # DECREF(x) refnanny complains since x is not got tracked yet
>> # INCREF(1)
>> x=1
>> # refnanny complains since there is no giveref for 1
>> bar()
>> # refnanny complains since 0 is not giveref-ed and 1 got giveref-ed
>> instead
>>
>>
>> For the inner function bar() it is easy to fix. But for the outer
>> function, since the thing x referenced to can be changed at every
>> point now, it will not work correctly to giveref at the end of
>> function.
>>
>> Since the rule is that closure variables are owned by scope object and
>> not managed by refnanny. So my idea to fix this is to wrap every
>> assignment to closure object by a pair of GOTREF and GIVEREF. So when
>> you do x=1, these will happen:
>>
>> GOTREF(x)
>> DECREF(x)
>> INCREF(1)
>> x=1
>> GIVEREF(x)
>>
>> Then refnanny will be happy.
>>
>
> Looks good ...
>
>> I implemented this, and got all the closure related tests passed
>> without refnanny complaining.
>>
>> This generate a bit more codes but I think should be ok. Since
>> refnanny is for debug so performance at here would not be a concern.
>>
>
> Of course, never mind about these extra lines...
>
>
>
> --
> Lisandro Dalcin
Thanks! :)
BTW, just spotted a closure bug, this won't compile (reports
'__pyx_outer_scope' redeclared):
def nested1():
def f():
def g1():
pass
def nested2():
def f():
def g2():
pass
Seems some name mangling problem. I traced to
CreateClosureClasses.create_class_from_scope() in
ParseTreeTransform.py then didn't get the idea yet.
Anyone want to look into it? Should I file it to issue tracker?
--
Haoyu BAI
School of Computing,
National University of Singapore.
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