Re: [Qemu-devel] [PATCH] nbd/trivial: fix type cast for ioctl

[Michael Tokarev]

03.04.2015 17:15, Paolo Bonzini wrote:
> On 03/04/2015 13:01, Bogdan Purcareata wrote:
...
>> -    if (ioctl(fd, NBD_SET_SIZE_BLOCKS, size / (size_t)BDRV_SECTOR_SIZE) < 
>> 0) {
>> +    if (ioctl(fd, NBD_SET_SIZE_BLOCKS, (size_t)(size / BDRV_SECTOR_SIZE) < 
>> 0)) {
>>          int serrno = errno;

Hmm..  I don't think this is right at all.  Now we compare size_t with zero,
the result is always false, and set error if ioctl return anything other than 0,
including any positive value.

Compare:

  if (ioctl(fd, NBD_SET_SIZE_BLOCKS, (size_t)(size / BDRV_SECTOR_SIZE) < 0))
  if (ioctl(fd, NBD_SET_SIZE_BLOCKS, (size_t)(size / BDRV_SECTOR_SIZE)) < 0)

I think the latter is the right version.

So much for trivial... ;)

Thanks,

/mjt