2012/10/11 Armin Rigo <ar...@tunes.org>:
> On Thu, Oct 11, 2012 at 7:41 AM, Stefan Behnel <stefan...@behnel.de> wrote:
>> 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 obmalloc.c is straight from CPython. It's very unlikely at this
> point to contain problems.
It looks like the typical hack of a "free list" implementation.
Freed blocks form a linked list, and the address of the next free
block is stored in the block itself.
So the line above effectively pops the first item in the list:
pool->freeblock is the address of the first free block,
PyObject_Malloc() will return it,
and pool->freeblock is changed to point to the next free block.
Everything looks normal to me, even if a bit obscure.
--
Amaury Forgeot d'Arc
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