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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] [PATCH] move -Wno-error=uninitialized to configure
Date: Tue, 30 Jun 2009 13:44:31 +0100
References: <20090630113949.GA32364@redhat.com>
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To: qemu-devel@nongnu.org
Cc: Laurent Desnogues <laurent.desnogues@gmail.com>, Anthony Liguori <aliguori@us.ibm.com>, "Michael S. Tsirkin" <mst@redhat.com>

On Tuesday 30 June 2009, Michael S. Tsirkin wrote:
> On Tue, Jun 30, 2009 at 03:12:40PM +0300, Michael S. Tsirkin wrote:
> > On Tue, Jun 30, 2009 at 01:07:34PM +0100, Paul Brook wrote:
> > > On Tuesday 30 June 2009, Michael S. Tsirkin wrote:
> > > > Move -Wno-error=uninitialized out of rules.mak and into configure.
> > > > Only use it if supported by compiler.
> > >
> > > Why? Shouldn't we be fixing the uninitialized variables?
> > >
> > > Paul
> >
> > gcc's algorithm for detecting uninitialized variables is
> > famously unreliable. Just scattering '= 0' around the code
> > masks the warning but hides the fact that application logic
> > might still be broken.
>
> To clarify: what's broken is that gcc has false positives in the logic.
> And if you work around this by adding initialization where it's not
> really required, you confuse other tools that would otherwise have a
> chance to detect an error.

In that case should we be using -Wno-uninitialized?

The whole point of -Werror is that it forces us to keep the code clean. Having 
to mentally filter out false positives just doesn't work. Once you have 
routinely expected warnings then people stop checking for new ones.

Paul