Re: [Qemu-devel] [PATCH] Permit zero-sized qemu_malloc() & friends

[malc]

On Sun, 6 Dec 2009, Avi Kivity wrote:

> On 12/06/2009 01:53 PM, malc wrote:
> > On Sun, 6 Dec 2009, Avi Kivity wrote:
> > 
> >    
> > > On 12/06/2009 12:22 PM, malc wrote:
> > >      
> > > > Here, i believe, you are inventing artificial restrictions on how
> > > > malloc behaves, i don't see anything that prevents the implementor
> > > > from setting aside a range of addresses with 31st bit set as an
> > > > indicator of "zero" allocations, and then happily giving it to the
> > > > user of malloc and consumming it in free.
> > > > 
> > > >        
> > > The implementation needs to track which addresses it handed out, since it
> > > is
> > > required that malloc(0) != malloc(0) (unless both are NULL).
> > >      
> > You haven't read carefully, i said range.
> >    
> 
> I did in fact.  Consider a loop
> 
>   malloc(0);
>   p = malloc(0);
>   while (1) {
>       n = malloc(0);
>       free(p);
>       p = n;
>   }
> 
> without some form of tracking, you won't be able to return unique addresses
> eventually.

So? There will be tracking, it's the same as with OpenBSD where
allocations of zero and greater than zero are handled differently.

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