Re: [PATCH for 7.2?] target/i386: Remove compilation errors when -Werror=maybe-uninitialized

[Peter Maydell]

On Wed, 7 Dec 2022 at 18:44, Eric Auger <eric.auger@redhat.com> wrote:
> On 12/7/22 19:23, Richard Henderson wrote:
> > Adding -Wall is not standard, nor all the other -W that you are
> > adding.  I think you should not be surprised that you run into problems.
> OK that's a useful indication. I used to have this configure cmd line
> for a while and have not paid much attention to it until now, I
> acknowledge. This was useful to catch compilation errors at some point I
> guess.
> >
> > While you can make a case for auditing the code base and adding these
> > to the default set of warning flags, that's a job for the next
> > development cycle.
>
> Let me clarify, I am not insisting for that fix to land in 7.2 all the
> more so it is pretty late. I just wanted to report the compilation issue
> and since I use the std qemu pieces with a pretty standard tool chain I
> thought somebody else would be likely to hit the same problem.

As Richard says, we don't expect people to randomly add extra
warning flags, and anybody who does should expect to see extra
warnings (and that they need to --disable-werror if they don't want
those extra warnings to turn into errors).

We specifically disable some warnings, there are some not-on-by-default
warnings that we know we have work to do if we want to eliminate them
(eg -Wvla) and there's probably a few where we conceptually disagree
with a warning flag or don't find it useful for QEMU (like
-Wgnu-statement-expression -- we deliberately use GNU statement
expressions so warning about them isn't useful to us).

Sorting through which of the currently non-enabled warning flags
are worth trying to fix existing warnings and enable by default
is a pretty big task (not dissimilar to sorting through Coverity
issue reports -- maybe some of the things you fix are real bugs
but there's a lot of false-positives to wade through to get there).

maybe-uninitialized warnings are particularly awkward because whether
you get them depends a lot on the version of the compiler and how
smart its data analysis is.

thanks
-- PMM