29.01.2019 13:32, Stefan Hajnoczi wrote:
> On Tue, Jan 29, 2019 at 6:24 PM Vladimir Sementsov-Ogievskiy
> <vsement...@virtuozzo.com> wrote:
>> 29.01.2019 6:31, Stefan Hajnoczi wrote:
>>> On Fri, Jan 25, 2019 at 07:46:01PM +0300, Vladimir Sementsov-Ogievskiy
>>> wrote:
>> Hmm. In this case we definitely will have tiny extra memory usage, but we
>> gain beautiful
>> readability.
>>
>> So, like this:
>>
>> diff --git a/include/qemu/iov.h b/include/qemu/iov.h
>> index 5f433c7768..53de1b38bb 100644
>> --- a/include/qemu/iov.h
>> +++ b/include/qemu/iov.h
>> @@ -134,9 +134,31 @@ typedef struct QEMUIOVector {
>> struct iovec *iov;
>> int niov;
>> int nalloc;
>> - size_t size;
>> + union {
>> + struct {
>> + void *__unused_iov_base;
>
> This could be struct iovec *iov for nalloc > 0 users. Must resist hackiness!
> :)
can't be iov, gcc complains:
include/qemu/iov.h:139:27: error: duplicate member ‘iov’
struct iovec *iov;
>
>> + size_t size;
>> + };
>> + struct iovec local_iov;
>> + };
>> } QEMUIOVector;
>
> That's clever and not too hacky. Please include a comment so the
> intent is clear:
>
> /* Save space by reusing the embedded iovec's size field as the
> total size field. Users with external iovecs don't use the embedded
> iovec so this is safe. */
>
> Stefan
>
--
Best regards,
Vladimir
