The direction of malloc?

[Florian Weimer]

On 12/16/2013 10:46 PM, Roland McGrath wrote:
>> The main purpose of malloc_get_state / malloc_set_state is for use by
>> emacs.  If emacs adopted a better approach I'd happily deprecate them -
>> turn them into compat symbols - but you still need to support them
>> indefinitely with existing emacs binaries, as a matter of binary
>> compatibility.  (Support could mean such binaries - binaries using the
>> malloc_set_state compat symbol - use a different copy of malloc in libc
>> from what all other binaries use, if necessary.)
>
> (I believe I've mentioned this before when discussing the ppc32 ABI
> situation.)  I'm pretty sure that the way Emacs uses malloc before dumping
> is such that there's no significant amount of allocation done then (if any)
> that will ever be freed later.  So for ABI compatibility it is probably
> sufficient to have a malloc_set_state call from an old binary result in the
> allocations made up to that point becoming unfreeable.

Could we fix this in Emacs somehow?  Or do we have to support old Emacs 
binaries forever?

-- 
Florian Weimer / Red Hat Product Security Team