Re: [Qemu-devel] [PATCH] Introduce QEMU_NEW()

[Markus Armbruster <armbru@redhat.com>]

Kevin Wolf <kwolf@redhat.com> writes:

> Am 25.07.2011 12:06, schrieb Stefan Hajnoczi:
>> On Mon, Jul 25, 2011 at 9:51 AM, Avi Kivity <avi@redhat.com> wrote:
>>> qemu_malloc() is type-unsafe as it returns a void pointer.  Introduce
>>> QEMU_NEW() (and QEMU_NEWZ()), which return the correct type.
>>>
>>> Signed-off-by: Avi Kivity <avi@redhat.com>
>>> ---
>>>
>>> This is part of my memory API patchset, but doesn't really belong there.
>>>
>>>  qemu-common.h |    3 +++
>>>  1 files changed, 3 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/qemu-common.h b/qemu-common.h
>>> index ba55719..66effa3 100644
>>> --- a/qemu-common.h
>>> +++ b/qemu-common.h
>>> @@ -186,6 +186,9 @@ void qemu_free(void *ptr);
>>>  char *qemu_strdup(const char *str);
>>>  char *qemu_strndup(const char *str, size_t size);
>>>
>>> +#define QEMU_NEW(type) ((type *)(qemu_malloc(sizeof(type))))
>>> +#define QEMU_NEWZ(type) ((type *)(qemu_mallocz(sizeof(type))))
>> 
>> Does this mean we need to duplicate the type name for each allocation?
>> 
>> struct foo *f;
>> 
>> ...
>> f = qemu_malloc(sizeof(*f));
>> 
>> Becomes:
>> 
>> struct foo *f;
>> 
>> ...
>> f = QEMU_NEW(struct foo);
>
> Maybe we should allow this and make it the usual pattern:
>
> f = qemu_new(typeof(*f));
>
> It's gcc specific, but we already don't care about portability to other
> compilers in more places.
>
> On the other hand, how many bugs did we have recently that were caused
> by a wrong sizeof for qemu_malloc? As far as I can say, there's no real
> reason to do it. I think it's the same kind of discussion as with
> forbidding qemu_malloc(0) (except that this time it just won't improve
> things much instead of being really stupid).

Side-stepping the stupid "OMG malloc(0) is weird, therefore we must make
qemu_malloc(0) differently weird" controversy would be useful all by
itself.