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

[Eduardo Habkost]

Excerpts from Markus Armbruster's message of Mon Nov 30 11:55:34 -0200 2009:
> Commit a7d27b53 made zero-sized allocations a fatal error, deviating
> from ISO C's malloc() & friends.  Revert that, but take care never to
> return a null pointer, like malloc() & friends may do (it's
> implementation defined), because that's another source of bugs.
> 
> Rationale: while zero-sized allocations might occasionally be a sign of
> something going wrong, they can also be perfectly legitimate.  The
> change broke such legitimate uses.  We've found and "fixed" at least one
> of them already (commit eb0b64f7, also reverted by this patch), and
> another one just popped up: the change broke qcow2 images with virtual
> disk size zero, i.e. images that don't hold real data but only VM state
> of snapshots.
> 
> If a change breaks two uses, it probably breaks more.  As a quick check,
> I reviewed the first six of more than 200 uses of qemu_mallocz(),
> qemu_malloc() and qemu_realloc() that don't have an argument of the form
> sizeof(...) or similar:

Acked-by: Eduardo Habkost <address@hidden>

This also makes qemu_realloc(NULL, size) completely equivalent to
qemu_malloc(size), and that's a good thing.
-- 
Eduardo