Re: memset (0, 0, 0);

Richard Earnshaw
2003-04-08T16:40:39Z

> On Tue, Apr 08, 2003 at 10:29:55AM +0100, Richard Earnshaw wrote:
> > >
> > > Hi Geoff,
> > >
> > > Which xmalloc are you referring to? The xmalloc in this case is a gdb internal function, defined in gdb/utils.c:
> > >
> > > PTR xmalloc (size_t size)
> > > {
> > > return xmmalloc (NULL, size);
> > > }
> > >
> > > And xmmalloc is:
> > >
> > > void * xmmalloc (void *md, size_t size)
> > > {
> > > void *val;
> > >
> > > if (size == 0)
> > > {
> > > val = NULL;
> > > }
> > > else
> > > {
> > > val = mmalloc (md, size);
> > > if (val == NULL)
> > > nomem (size);
> > > }
> > > return (val);
> > > }
> > >
> > > So size=0 does indeed return NULL. Also, I have single stepped this code to verify that this is actually what happens.
> >
> > It looks as though that implementation of xmalloc doesn't match the
> > general specification of xmalloc, which is that xmalloc must *never*
> > return NULL (see libiberty/xmalloc.c for the specification).
> >
> > I'm not sure why gdb is trying to provide its own implementation of these
> > functions and not use those in libiberty. Andrew?
>
> The ones in libiberty call exit; the ones in gdb call error() and
> unwind cleanups. GDB prefers not to abort when it runs out of memory,
> esp. if it can just abort the current operation and reclaim memory.
>

That's ok, but the bit about returning NULL isn't. If we want a "malloc"
routine that always returns NULL on zero size, we shouldn't call it
xmalloc.

R.