Re: [2.6.29-rc2-git2] compilation warnings

Ingo Molnar
2009-01-27T13:06:33Z

* Jean Delvare <khali@linux-fr.org> wrote:

> Hi Takashi,
>
> On Tue, 27 Jan 2009 10:34:20 +0100, Takashi Iwai wrote:
> > At Tue, 27 Jan 2009 09:46:28 +0100,
> > > On Tue, 27 Jan 2009 08:32:17 +0100, Takashi Iwai wrote:
> > > > A bogus warning. Ignore this.
> > >
> > > No matter how bogus it is, it should be fixed. Otherwise this is
> > > wasting the time of users and developers over and over again.
> >
> > Well, it's a bug of gcc appearing only in a certain version, so most
> > people won't see it.
> >
> > Of course, we can put uninitialized_var(). But, I don't basically
> > like adding it unconditionally...
>
> I didn't know about uninitialized_var(), thanks for the hint.
>
> My experience with these warnings is that, in many cases, it is possible
> to write the code differently so that it is clear to the compiler that
> the variable is never used uninitialized. In some cases, doing so also
> makes the code easier to read for humans and less likely to break in the
> future.
>
> Of course, in some cases the problem is simply that the compiler is too
> stupid to understand even simple things, but in other cases these
> warnings might be a good opportunity to rewrite the code in a way that
> is easier to understand.

And even in the cases where the compiler is stupid, leaving a warning
around:

1) Does not get compiler bugs fixed any faster [only true competition
between compilers gets compiler bugs fixed any faster]

2) Has ongoing and irreversible maintenance costs for _all of us in the
kernel_

3) for every bogus compiler warning there's a dozen warnings where the
compiler told us that _we_ were doing something stupid. All things
considered the false positive ratio is still a fair deal.

So leaving them around is a bit like making a political point by burning
yourself in front of the cameras - leaves the political opponent largely
unimpressed and unscathed while being self-destructive in 99% of the
cases.

gcc_is_utterly_stupid(var) type of annotations (that initialize to zero
instead of the current 'turn off the warning' dangerous construct) would
be far better. Albeit even that would in all likelyhood be a rather
pointless (but admittedly satisfying) gesture.

Ingo