Re: [PATCH] ArmPlatformPkg: eliminate Juno gcc build warning

[Leif Lindholm <leif.lindholm@linaro.org>]

On Tue, Jun 20, 2017 at 01:28:38PM +0200, Ard Biesheuvel wrote:
> (+ Laszlo)
> 
> On 20 June 2017 at 13:00, Leif Lindholm <leif.lindholm@linaro.org> wrote:
> > When building without LTO, gcc incorrectly resolves the hazards for
> > 'PciRegBase’ when inlining, leading to "may be used uninitialized"
> > warnings (and hence build failure with -Werror).
> > Eliminate this warning by explicitly initializing the variable to 0.
> >
> > Contributed-under: TianoCore Contribution Agreement 1.0
> > Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
> 
> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Thanks!

> > ---
> >
> > For those who have heard me mentioning this before but arguing against
> > upstreaming this patch: I only just tweaked that this warning doesn't
> > go away with more recent toolchains, but simply when switching to GCC5
> > build profile, and hence LTO. Build failure still reproducible with
> > gcc 6.3.1 and GCC49.
> 
> /me annoyed

+1

> We keep hitting this with GCC, and I profoundly dislike having to add
> redundant initialization sequences. Is there any other solution
> possible, e.g., disable this warning for certain builds?

I would really like to not disable it.
When it gets it right, that's usually a pretty horrific bug caught.
And if we switch to LTO as the norm, I guess these will become less
noticeable over time.
But it does bug me too.

/
    Leif

> >  ArmPlatformPkg/ArmJunoPkg/Drivers/ArmJunoDxe/ArmJunoDxe.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/ArmPlatformPkg/ArmJunoPkg/Drivers/ArmJunoDxe/ArmJunoDxe.c b/ArmPlatformPkg/ArmJunoPkg/Drivers/ArmJunoDxe/ArmJunoDxe.c
> > index da93eb5829..18491c7378 100644
> > --- a/ArmPlatformPkg/ArmJunoPkg/Drivers/ArmJunoDxe/ArmJunoDxe.c
> > +++ b/ArmPlatformPkg/ArmJunoPkg/Drivers/ArmJunoDxe/ArmJunoDxe.c
> > @@ -343,6 +343,7 @@ ArmJunoSetNicMacAddress ()
> >      return Status;
> >    }
> >
> > +  PciRegBase = 0;
> >    Status = InitPciDev (PciIo, &PciRegBase, &OldPciAttr);
> >    if (EFI_ERROR (Status)) {
> >      return Status;
> > --
> > 2.11.0
> >