Hi Grame
Graeme Russ graeme.russ@gmail.com wrote on 2012/04/02 09:17:44:
Hi Joakim, On Apr 2, 2012 4:55 PM, "Joakim Tjernlund" joakim.tjernlund@transmode.se wrote:
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
Forget aboug other implementations... What matters is that the fact that the behaviour is undefined and it is up to the caller to take that into account
Well, u-boot borrows code from both kernel and user space so it would make sense if malloc(0) behaved the same. Especially for kernel code which tend to depend on the kernels impl.(just look at Scotts example)
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;
That could work, but technically I don't think it complies as it is not a pointer to allocated memory...
It doesn't not have to be allocated memory, just a ptr != NULL which you can do free() on.
Jocke