[U-Boot] [PATCH] Prevent malloc with size 0

Joakim Tjernlund
2012-04-02T06:55:24Z

>
> Hi Marek,
>
> On Mon, Apr 2, 2012 at 1:36 PM, Marek Vasut <marek.vasut@gmail.com> wrote:
> > Dear Mike Frysinger,
> >
> >> On Sunday 01 April 2012 20:25:44 Graeme Russ wrote:
> >> > b) The code calling malloc(0) is making a perfectly legitimate assumption
> >> >
> >> > ? ?based on how glibc handles malloc(0)
> >>
> >> not really. ?POSIX says malloc(0) is implementation defined (so it may
> >> return a unique address, or it may return NULL). ?no userspace code
> >> assuming malloc(0) will return non-NULL is correct.
> >
> > Which is your implementation-defined ;-) But I have to agree with this one. So
> > my vote is for returning NULL.
>
> Also, no userspace code assuming malloc(0) will return NULL is correct
>
> Point being, no matter which implementation is chosen, it is up to the
> caller to not assume that the choice that was made was, in fact, the
> choice that was made.
>
> I.e. the behaviour of malloc(0) should be able to be changed on a whim
> with no side-effects
>
> So I think I should change my vote to returning NULL for one reason and
> one reason only - It is faster during run-time

Then u-boot will be incompatible with both glibc and the linux kernel, it seems
to me that any modern impl. of malloc(0) will return a non NULL ptr.

It does need to be slower, just return ~0 instead, the kernel does something similar:
if (!size)
return ZERO_SIZE_PTR;

Jocke