[pypy-dev] Weird C code in crashing code line

[Maciej Fijalkowski]

On Thu, Oct 11, 2012 at 7:41 AM, Stefan Behnel <stefan_ml at behnel.de> wrote:
> Hi,
>
> I get a crash in lxml's test suite on 64bit Linux, right with the first
> test. I couldn't investigate it in depth so far, but at least I found that
> it crashes in line 606 of obmalloc.c, which reads as follows:
>
>     583    block *bp;
>     [...]
>     604         bp = pool->freeblock;
>     605         assert(bp != NULL);
>     606         if ((pool->freeblock = *(block **)bp) != NULL) {
>
> The cast looks a bit smelly to me. Could someone who knows that code please
> take a look to see if it makes any sense? This kind of code tends to hint
> at potential aliasing problems to me etc. OTOH, "bp" holds the value 0xc
> here when it crashes, so there's clearly something going wrong.

That's very likely a refcounting problem (not that I can help much
more than that though :(

Cheers,
fijal