[Cython] Debugging a segfault in a cython generated module

[Stefan Behnel]

Hi,

Brian Granger wrote:
> I am realizing that this is also a problem.  I was creating a memory
> leak by having both the subclass and superclass do allocations in
> their own __cinit__.  The trick you propose:
> 
> cdef class Foo:
> 
>   cdef __cinit__(self):
>     self._actual_cinit(self)
>   cdef _actual_cinit(self):
>     foo_ptr = doTheAllocation()
> 
> cdef class Bar(Foo):
> 
>   cdef _actual_cinit(self):
>     bar_ptr = doTheAllocation()
> 
> When I try this pattern Foo's _actual_cinit *always gets called.*  I
> looked at the generated C code and it look like this:
> 
> __pyx_1 = ((struct __pyx_vtabstruct_6txbase_Foo *)((struct
> __pyx_obj_6txbase_Foo *)__pyx_v_self)->__pyx_vtab)->_actualCinit()
>
> When I made _actualCinit(), I got an attribute error (which makes
> sense as the Python side of the class has not been built yet.)
> 
> Why is the vtable not finding the right _actualCinit implementation?
> Is this a bug, or is this to be expected because the class has not
> been fully built.

Hmmm, this should work (but in case vtab is not initialised correctly at this
point, I would consider that a bug).


> Also, why can't I just do the allocations in the __init__ method?
> That has a much more flexible and explicit approach when dealing with
> subclasses.

The call to __init__() is a Python thing. Imagine a subclass that overrides
__init__ and forgets to make a super() call.

Stefan