[Cython] Bug, or changed array assignment in 0.17beta1?

[Stefan Behnel]

Stefan Behnel, 25.07.2012 08:29:
> Stefan Behnel, 25.07.2012 07:40:
>> Mike Zaletel, 25.07.2012 00:40:
>>> --------bug.pyx----------
>>>
>>> def foo():
>>>        cdef int i
>>>        cdef int* p1 = [4, 4]
>>>        cdef int* p2 = [5, 5]
>>>
>>>        print "p1:",
>>>        for i in range(2):
>>>                print p1[i],
>>>        print "\np2:",
>>>        for i in range(2):
>>>                print p2[i],
>>>
>>> -----------------------------
>>>
>>> which in Cython 0.17beta1 gives me
>>>
>>> >>> import bug
>>> >>> bug.foo()
>>> p1: 5 5
>>> p2: 5 5
>>>
>>>
>>> while in Cython 0.16 I get
>>>
>>> >>> import bug
>>> >>> bug.foo()
>>> p1: 4 4
>>> p2: 5 5
>>
>> The problem is that the same (temporary) local array variable is used in
>> both cases to build the array, and then only a pointer is assigned, i.e. p1
>> and p2 then point to the same array, which gets overwritten with the new
>> values in the second assignment.
> 
> Looking into this some more, the problem arises from the pointer
> assignment, because the left side is a pointer variable whereas the right
> side is a temp value. Temps aren't really made for an enduring life. Here,
> the array temp variable is being freed after the assignment and then
> reused. We could fix it by not freeing the temp, or at least by not reusing
> it

Ah, found the existing hack that aimed to do that and fixed it. :)

https://github.com/cython/cython/commit/557b8ed7dfdb9155327e481bef4522a9214695e9

Stefan