Re: Prevent compiler warning on block.c

[Kevin Wolf <kwolf@redhat.com>]

Am 09.06.2021 um 09:12 hat Thomas Huth geschrieben:
> On 05/05/2021 10.05, Vladimir Sementsov-Ogievskiy wrote:
> > 05.05.2021 10:59, Miroslav Rezanina wrote:
> > > Commit 3108a15cf (block: introduce bdrv_drop_filter()) introduced
> > > uninitialized
> > > variable to_cow_parent in bdrv_replace_node_common function that is
> > > used only when
> > > detach_subchain is true. It is used in two places. First if block
> > > properly initialize
> > > the variable and second block use it.
> > > 
> > > However, compiler treats this two blocks as two independent cases so
> > > it thinks first
> > > block can fail test and second one pass (although both use same
> > > condition). This cause
> > > warning that variable can be uninitialized in second block.
> > > 
> > > To prevent this warning, initialize the variable with NULL.
> > > 
> > > Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
> > > ---
> > > diff --git a/block.c b/block.c
> > > index 874c22c43e..3ca27bd2d9 100644
> > > --- a/block.c
> > > +++ b/block.c
> > > @@ -4851,7 +4851,7 @@ static int
> > > bdrv_replace_node_common(BlockDriverState *from,
> > >       Transaction *tran = tran_new();
> > >       g_autoptr(GHashTable) found = NULL;
> > >       g_autoptr(GSList) refresh_list = NULL;
> > > -    BlockDriverState *to_cow_parent;
> > > +    BlockDriverState *to_cow_parent = NULL;
> > >       int ret;
> > > 
> > >       if (detach_subchain) {
> > > 
> > 
> > Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> 
> This just popped up again here:
> 
>  https://lists.gnu.org/archive/html/qemu-devel/2021-06/msg02067.html
> 
> Kevin, Max, could you please pick it up to get this problem fixed?

Thanks for pinging, seems the intended refactoring hasn't happened.

I've applied this one to my block branch now.

Kevin