Re: [PATCH] migration/qemu-file: Fix maybe uninitialized on qemu_get_buffer_in_place()

[Wainer dos Santos Moschetta]

Hi,

On 1/28/21 3:07 PM, Philippe Mathieu-Daudé wrote:
> On 1/28/21 6:16 PM, Dr. David Alan Gilbert wrote:
> > * Wainer dos Santos Moschetta (wainersm@redhat.com) wrote:
> > > Fixed error when compiling migration/qemu-file.c with 
> > > -Werror=maybe-uninitialized
> > > as shown here:
> > >
> > > ../migration/qemu-file.c: In function 'qemu_get_buffer_in_place':
> > > ../migration/qemu-file.c:604:18: error: 'src' may be used uninitialized in this 
> > > function [-Werror=maybe-uninitialized]
> > >    604 |             *buf = src;
> > >        |             ~~~~~^~~~~
> > > cc1: all warnings being treated as errors
> > >
> > > Signed-off-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
> > Yes, I think I had a discussion with someone about this recently but
> > can't find it;
> Maybe with Thomas, he reported that 2 years ago when building with -O3:
> https://www.mail-archive.com/qemu-devel@nongnu.org/msg599522.html


I saw that error when compiling QEMU with -O3 as well.


> > the compiler is technically correct, but the only time
> > it's unitialised is the case where it's result doesn't matter.
> >
> > Still, to shut the compiler up:
> >
> >
> > Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>


Thanks David!


> > > ---
> > > Passed on CI: https://gitlab.com/wainersm/qemu/-/pipelines/247801576
> > >
> > >   migration/qemu-file.c | 2 +-
> > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/migration/qemu-file.c b/migration/qemu-file.c
> > > index be21518c57..d6e03dbc0e 100644
> > > --- a/migration/qemu-file.c
> > > +++ b/migration/qemu-file.c
> > > @@ -595,7 +595,7 @@ size_t qemu_get_buffer_in_place(QEMUFile *f, uint8_t **buf, 
> > > size_t size)
> > >   {
> > >       if (size < IO_BUF_SIZE) {
> > >           size_t res;
> > > -        uint8_t *src;
> > > +        uint8_t *src = NULL;
> > >   
> > >           res = qemu_peek_buffer(f, &src, size, 0);
> > >   
> > > --
> > > 2.28.0