[PATCH] Add reallocarray function.

[Zack Weinberg]

On Mon, Apr 10, 2017 at 11:00 AM, Dennis Wölfing <denniswoelfing@gmx.de> wrote:
> The reallocarray function is an extension from OpenBSD.  It is an
> integer-overflow-safe replacement for realloc(p, X*Y) and
> malloc(X*Y) (realloc(NULL, X*Y)).  It can therefore help in preventing
> certain security issues in code.
>
> This is an updated version of a patch originally submitted by Rüdiger
> Sonderfeld in May 2014.
> See <https://sourceware.org/ml/libc-alpha/2014-05/msg00481.html>.

I agree in principle with adding this function.  I skimmed the patch
and it seems to be mostly the Right Thing.  I do have two concerns:

* There do not appear to be any uses of the internal aliases
__libc_reallocarray and __reallocarray.  Have you audited glibc itself
for places that should use reallocarray?  If you haven't, would you be
willing to do that?  This will determine whether we actually need
those aliases.

* Please add documentation for reallocarray.  It belongs in
manual/memory.texi, in the "Changing Block Size" section.  This is the
place to explain when and why one should use reallocarray instead of
realloc.

zw