[Python-Dev] RE: test_sort.py failure

[Guido van Rossum]

> The following (just checked in) changes should solve the problem:
> 
> * drop the unreasonable list invariant that ob_item should never come back
>   to NULL during the lifetime of the object.
> 
> * listobject.c nevertheless did not conform to the other invariants,
>   either; fixed.
> 
> * listobject.c now uses list_clear() as the obvious internal way to clear
>   a list, instead of abusing list_ass_slice() for that.  It makes it easier
>   to enforce the invariant about ob_item == NULL.
> 
> * listsort() sets allocated to -1 during sort; any mutation will set it
>   to a value >= 0, so it is a safe way to detect mutation.  A negative
>   value for allocated does not cause a problem elsewhere currently.
>   test_sort.py has a new test for this fix.
> 
> * listsort() leak: if items were added to the list during the sort, AND if
>   these items had a __del__ that puts still more stuff into the list,
>   then this more stuff (and the PyObject** array to hold them) were
>   overridden at the end of listsort() and never released.

Wow.  I'm impressed.  Thanks!

BTW, I just wrote a little programing for playing Conway's Game of
Life, using Tkinter.  (Yes, I was inspired by Damien Conway's (no
relation) talk Tuesday night at OSCON.)  Anyway, it runs at about 5.35
generations/second in Python 2.3, and 6.35 generations/second in
Python 2.4.  Good job everyone!

--Guido van Rossum (home page: http://www.python.org/~guido/)