Re: [RFC] Supporting malloc_usable_size

[Siddhesh Poyarekar <siddhesh@gotplt.org>]

On 2022-12-07 05:01, Florian Weimer wrote:
> * Siddhesh Poyarekar:
> 
>> On 2022-12-05 15:35, Florian Weimer via Libc-alpha wrote:
>>> I think it's a backwards-incompatible change.  The existing manual page
>>> documents the function as MT-Safe.
>>> With this new policy, I don't think malloc_usable_size is useful for
>>> anything at all, and we can just deprecate it (with a deprecation
>>> warning message) and eventually remove it from linking (after
>>> considering the impact on replacement malloc implementations, but I
>>> don't think it will be problematic).
>>
>> We don't have consensus on deprecation unfortunately.  DJ is of the
>> opinion that the limited use (knowing the usable size but not being
>> able to do anything with it) may be useful enough for some programs.
>> With that position, making it clear that the extra space is never
>> safely usable and then just leaving it at that is probably the least
>> worst out.
> 
> Maybe we could add a deprecation warning just for -D_FORTIFY_SOURCE=3?

I'm all for deprecation, at least partial if not full.

Thanks,
Sid