Re: Prevent compiler warning on block.c

[Miroslav Rezanina <mrezanin@redhat.com>]

----- Original Message -----
> From: "Peter Maydell" <peter.maydell@linaro.org>
> To: "Miroslav Rezanina" <mrezanin@redhat.com>
> Cc: "QEMU Developers" <qemu-devel@nongnu.org>, "Vladimir Sementsov-Ogievskiy" <vsementsov@virtuozzo.com>,
> "Qemu-block" <qemu-block@nongnu.org>
> Sent: Wednesday, May 5, 2021 12:43:44 PM
> Subject: Re: Prevent compiler warning on block.c
> 
> On Wed, 5 May 2021 at 09:06, Miroslav Rezanina <mrezanin@redhat.com> 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.
> 
> If fixing compiler warnings, please quote the compiler name/version
> in the commit message. (This helps with understanding whether the issue
> is because of an older and not-smart-enough compiler or a new bleeding-edge
> compiler with extra checking.)

Hi Peter,

sorry for missing version. I was going to put the version in but got distracted when checking versions.

This warning occurs using GCC 8.4.1 and 11.0.1.

Mirek

> 
> thanks
> -- PMM
> 
> 

-- 
Miroslav Rezanina
Software Engineer - Virtualization Team Maintainer