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Re: [Qemu-trivial] [Qemu-devel] [PATCH] block: Fix compiler warning (-We
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-trivial] [Qemu-devel] [PATCH] block: Fix compiler warning (-Werror=uninitialized) |
Date: |
Fri, 20 Sep 2013 12:42:14 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Thu, Sep 19, 2013 at 06:59:23PM +0200, Andreas Färber wrote:
> Am 17.09.2013 18:43, schrieb Stefan Weil:
> > The patch fixes a warning from gcc (Debian 4.6.3-14+rpi1) 4.6.3:
> >
> > block/stream.c:141:22: error:
> > ‘copy’ may be used uninitialized in this function [-Werror=uninitialized]
> >
> > This is not a real bug - a better compiler would not complain.
> >
> > Now 'copy' has always a defined value, so the check for ret >= 0
> > can be removed.
> >
> > Signed-off-by: Stefan Weil <address@hidden>
> > ---
> > block/stream.c | 5 ++---
> > 1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/block/stream.c b/block/stream.c
> > index 078ce4a..fc19194 100644
> > --- a/block/stream.c
> > +++ b/block/stream.c
> > @@ -108,7 +108,7 @@ static void coroutine_fn stream_run(void *opaque)
> >
> > for (sector_num = 0; sector_num < end; sector_num += n) {
> > uint64_t delay_ns = 0;
> > - bool copy;
> > + bool copy = false;
> >
> > wait:
> > /* Note that even when no rate limit is applied we need to yield
> > @@ -123,7 +123,6 @@ wait:
> > STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, &n);
> > if (ret == 1) {
> > /* Allocated in the top, no need to copy. */
> > - copy = false;
> > } else if (ret >= 0) {
> > /* Copy if allocated in the intermediate images. Limit to the
> > * known-unallocated area [sector_num, sector_num+n). */
>
> Sorry for not spotting this patch earlier. This hunk looks wrong and
> needs to be dropped, I believe. In the ret >= 0 && copy case, there is a
> "goto wait" which would now no longer be able to go from copy == true ->
> copy == false. Not sure if that can happen in practice.
Thanks for catching this!
I've dropped the patch from my block tree for now.
Stefan