On Thu, Oct 30, 2025 at 10:59 AM Alejandro Colomar via Std-Proposals <
std-proposals_at_[hidden]> wrote:

> On Thu, Oct 30, 2025 at 07:27:38AM -0700, Thiago Macieira via
> Std-Proposals wrote:
> > On Wednesday, 29 October 2025 14:24:23 Pacific Daylight Time Thiago
> Macieira
> > via Std-Proposals wrote:
> > > I disagree because I don't want to wait for that operation. I want
> > > relocations now. In fact, I want them in 2005, when Qt began doing them
> > > anyway. It's memcpy/memmove, period.
> >
> > Oh, and realloc(). That's actually the most important one.
> >
> > I'll accept a replacement function if realloc() can't be fixed.
>
> I don't know if realloc(3) has any issues in C++, but if you mean the
> issues that C also has, we're in the process of fixing them.
> <https://www.austingroupbugs.net/view.php?id=1949>
> <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3621.txt>
>

That seems to address only the "unhappiest path" where the caller is
literally trying to do realloc(p, 0). Nobody does that in practice [he
says, hyperbolically].
I'm sure the API issues Thiago is talking about concern the "happy path."
Things like:

- Sometimes when I call `realloc`, the buffer doesn't move, and so
pointers/iterators/references aren't invalidated. How can I tell when this
happens? (In practice I think this is easy, but technically at least in C++
it's UB even to read the *pointer value* of the old, freed pointer in order
to equality-compare it with the new pointer.)
- Sometimes when I call `malloc` or `realloc`, the returned buffer actually
has more capacity than I asked for. How can I tell the true capacity of the
buffer? <https://stackoverflow.com/a/48612539/1424877>
- Sometimes when I call `malloc` or `realloc`, I'd *like* N bytes, but I'd
be *satisfied* to fall back to M. How can I communicate this to the system?
- Almost always when I call `malloc` or `realloc`, I care about the
alignment of the buffer. How can I communicate my alignment requirement to
the system? (There is still no aligned_realloc.)
<https://stackoverflow.com/questions/56619623/why-is-there-no-aligned-realloc-on-most-platforms>

Thiago may have been thinking of even more/different API issues, too.

HTH,
Arthur