Re: [Qemu-devel] [PATCH V4 2/6] qcow2: add error message in qcow2_write_snapshots()

[Wenchao Xia]

于 2013/11/5 3:46, Eric Blake 写道:
> On 11/03/2013 06:48 PM, Wenchao Xia wrote:
> > > On 14.10.2013 23:52, Wenchao Xia wrote:
> > > > The function still returns int since qcow2_snapshot_delete() will
> > > > return the number.
>
>
> > > > @@ -227,24 +239,40 @@ static int
> > > > qcow2_write_snapshots(BlockDriverState *bs)
> > > >
> > > >            ret = bdrv_pwrite(bs->file, offset, &h, sizeof(h));
> > > >            if (ret < 0) {
> > > > +            error_setg(errp,
> > > > +                       "Failed in write of snapshot header at %"
> > > > +                       PRIi64 " with size %" PRIu64 ": %d (%s)",
> > > > +                       offset, sizeof(h), ret, strerror(-ret));
> > >
> > > Again, on 32 bit systems, sizeof(size_t) is generally 4 and not 8 (you
> > > may want to cast sizeof(h) to int and just use %d).
> >
> >    Maybe caset as (int64_t)sizeof(h) to avoid possible incomplete value?
>
> If we have objects larger than 2G (such that sizeof(h) would require
> more than 31 bits), we have other issues to worry about.  Casting to int
> and using %d is safe enough.
 OK, will use %d.