Re: [musl] [PATCH] implement recallocarray(3)

[Ariadne Conill <ariadne@dereferenced.org>]

On Saturday, 1 August 2020 09:52:28 MDT Markus Wichmann wrote:
> On Sat, Aug 01, 2020 at 08:46:58AM -0600, Ariadne Conill wrote:
> > +void *recallocarray(void *ptr, size_t om, size_t m, size_t n)
> > +{
> > +	void *newptr;
> > +	size_t old_size, new_size;
> > +
> > +	if (n && m > -1 / n) {
> > +		errno = ENOMEM;
> > +		return 0;
> > +	}
> > +	new_size = m * n;
> > +
> > +	if (n && om > -1 / n) {
> > +		errno = EINVAL;
> > +		return 0;
> > +	}
> > +	old_size = om * n;
> > +
> > +	if (new_size <= old_size) {
> > +		memset((char *) ptr + new_size, 0, old_size - new_size);
> > +	}
> > +
> > +	newptr = reallocarray(ptr, m, n);
> > +	if (new_size > old_size) {
> > +		memset((char *) ptr + old_size, 0, new_size - old_size);
> > +	}
> > +
> > +	return newptr;
> > +}
> 
> Is there a reason for the call to reallocarray? The multiplication m * n
> has already been tested for overflow and executed at that point. Might
> as well just call realloc() there, right?

Good catch.  I decided to use reallocarray() simply for clarity, but I can 
change it to a realloc() call.

Ariadne