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

[Blue Swirl <blauwirbel@gmail.com>]

On Sat, Dec 5, 2009 at 5:07 PM, Avi Kivity <avi@redhat.com> wrote:
> On 12/04/2009 06:49 PM, Anthony Liguori wrote:
>>
>> I still believe that it is poor practice to pass size==0 to *malloc().  I
>> think actively discouraging this in qemu is a good thing because it's a
>> broken idiom.
>
> Why?  Unless we have a separate array allocator (like C++'s new and new[]),
> we need to support zero-element arrays without pushing the burden to callers
> (in the same way that for () supports zero iteration loops without a
> separate if ()).

Running a loop zero or nonzero number of times always has a very clear
and precise meaning. A pointer returned from allocating zero or
nonzero number of items may be completely unusable or usable,
respectively.

I think Laurent's proposal would work. We even could go so far as
rename the current function as qemu_malloc_possibly_broken (and adjust
callers mechanically) and introduce two new versions, which handle the
zero case in clearly advertised ways. Patches would fix the callers to
use the correct one.