[musl] Re: realloci(): A realloc() variant that works in-place

[Paul Eggert]

On 10/31/25 14:13, Alejandro Colomar wrote:

> Consider that realloci() would be significantly cheaper than realloc(3),

Not in the case where the object doesn't move: they should be about the 
same speed. And when the object grows so much that it does need to move, 
the V7 realloc approach should be a bit faster because you need to make 
just one call into the memory subsystem, not three (realloci + malloc + 
free).

> That would make sanitizers and static analyzers unable to verify lots of
> code
No, just the opposite. Currently sanitizers etc. spend useless work 
checking for C23 rules that don't correspond to any hardware or 
correctness needs; they're simply rules imposed by the C committee. This 
checking is counterproductive to real-world software development.

If we fixed the realloc spec to better match how actual production 
hardware behaves, we could fix sanitizers to spend their time flagging 
real bugs instead of wasting their time (and developers' time) 
generating false alarms.

> I wouldn't categorize it as hard to explain:
Oh, it's not hard to specify a realloci API, or to implement it. What's 
hard is explaining its motivation: why it's needed and what it's good 
for. It's motivated by specialized applications that most programmers 
don't know about and don't need to. And these specialized applications 
would be better served by a 7th Edition Unix realloc.