[PATCH] calloc should not duplicate malloc logic.

[Florian Weimer]

On 02/21/2014 04:04 PM, Ondřej Bílka wrote:
> Hi,
>
> To make future improvements of allocator simpler we could for now calloc
> just call malloc and memset. With that we could omit a changes that
> would duplicate malloc changes anyway.
>
> It would temporarily decrease its performance, which is not primary
> concern now as we just started release cycle.

I tested the current implementation (well, in 2.18 in Fedora 20), and it 
does not avoid the memset for large arrays, at least I see an RSS value 
that matches the size of the allocated array.  So I suppose this change 
is okay because it does not seem likely it adds further breakage for 
applications which rely on memory overcommit.

 > In long time horizon it would improve maintainability and performance,
 > my plan now is add a parameter used_by_calloc to internal malloc to
 > keep logic together. We could not do it without some refactoring as
 > int_malloc now has arena in parameter which is thing that I want to
 > deduplicate.

An additional return value from the internal malloc, indicating whether 
the memory is fresh/zeroed might be more appropriate.

-- 
Florian Weimer / Red Hat Product Security Team