Re: [PATCH] mm/vmscan: avoid false-positive -Wuninitialized warning

[Yuanchu Xie]

Hi Andrew and Arnd,

On Fri, Feb 13, 2026 at 11:23 AM Andrew Morton
<akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Fri, 13 Feb 2026 18:07:04 +0100 "Arnd Bergmann" <arnd@xxxxxxxx> wrote:
>
> > On Fri, Feb 13, 2026, at 17:58, Andrew Morton wrote:
> > > On Fri, 13 Feb 2026 13:38:56 +0100 Arnd Bergmann <arnd@xxxxxxxxxx> wrote:
> > >
> > >> From: Arnd Bergmann <arnd@xxxxxxxx>
> > >>
> > >> When the -fsanitize=bounds sanitizer is enabled,
> > >
> > > Is this an option in current kernels?
> >
> > Yes, this is CONFIG_UBSAN_ARRAY_BOUNDS. The actual warning
> > only shows up in some configurations with that, so either there
> > is some other dependency, or an element of chance based on gcc
> > optimizations.
>
> OK, I'll put a cc:stable on this, as people will want to compile older
> kernels with gcc-16.
>
> Aiming for upstreaming into 7.1-rc1 unless it's more urgent than I
> think.
>
> > > Seems a large change just to squish a compiler warning.  People might
> > > prefer a simple
> > >
> > > -   struct ctrl_pos sp, pv;
> > > +   struct ctrl_pos sp, pv = {};
> >
> > Right, that would clearly also shut up the warning.
> >
> > To me this seems less intuitive without an extra comment,
> > since read_ctrl_pos() is meant to initialize the entire
> > struct, but please pick whichever you find most readable
> > here.
>
> Let's see what the MGLRU maintainers have to say.

I went over the various cases of read_ctrl_pos and couldn't find
anything wrong (let me know if I'm mistaken), so this seems like a
mild compiler bug we're trying to work around. Given it's one single
version of gcc, I'm a fan of the simple `struct ctrl_pos sp, pv = {};`
with a comment.

Thanks,
Yuanchu