linux-kernel - Re: linux-next: build warning after merge of the drivers-x86 tree

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Date:   Thu, 15 Dec 2016 11:02:19 +1100
From:   Stephen Rothwell <sfr@...b.auug.org.au>
To:     Darren Hart <dvhart@...radead.org>
Cc:     linux-next@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lyude <lyude@...hat.com>,
        Henrique de Moraes Holschuh <hmh@....eng.br>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: linux-next: build warning after merge of the drivers-x86 tree

Hi Darren,

On Wed, 14 Dec 2016 14:59:14 -0800 Darren Hart <dvhart@...radead.org> wrote:
>
> On Wed, Dec 14, 2016 at 02:21:38PM -0800, Darren Hart wrote:
> > On Wed, Dec 14, 2016 at 01:50:44PM +1100, Stephen Rothwell wrote:  
> > > 
> > > After merging the drivers-x86 tree, today's linux-next build (x86_64
> > > allmodconfig) produced this warning:
> > > 
> > > In file included from include/linux/kernel.h:13:0,
> > >                  from drivers/platform/x86/thinkpad_acpi.c:52:
> > > drivers/platform/x86/thinkpad_acpi.c: In function 'hotkey_init':
> > > include/linux/printk.h:299:2: warning: 'type' may be used uninitialized in this function [-Wmaybe-uninitialized]
> > >   printk(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
> > >   ^
> > > drivers/platform/x86/thinkpad_acpi.c:3147:8: note: 'type' was declared here
> > >   char *type;
> > >         ^
> > > In file included from include/linux/kernel.h:13:0,
> > >                  from drivers/platform/x86/thinkpad_acpi.c:52:
> > > include/linux/printk.h:299:2: warning: 'in_tablet_mode' may be used uninitialized in this function [-Wmaybe-uninitialized]
> > >   printk(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
> > >   ^
> > > drivers/platform/x86/thinkpad_acpi.c:3146:6: note: 'in_tablet_mode' was declared here
> > >   int in_tablet_mode, res;
> > >       ^
> > > 
> > > Introduced by commit
> > > 
> > >   b31800283868 ("platform/x86: thinkpad_acpi: Move tablet detection into separate function")
> > > 
> > > I can't tell if this is a false positive or not.  
> > 
> > That's an uninitialized local variable. Not sure how I missed that. I'll
> > fix it up today. Thank you for the report.  
> 
> OK, no, it's a false positive because tp_features.hotkey_tablet is assigned in
> both places where in_tablet_mode is assigned, and if the former is 0 (global
> scope), the function returns without calling pr_info.

How about "type".

> Lyude, Henrique, please confirm.
> 
> Regardless, I'll add a patch to init in_tablet_mode to 0 so it is explicit - but
> will not rebase as it isn't technically an error.

No problem, it is only a warning after all.

-- 
Cheers,
Stephen Rothwell