linux-kernel - Re: [PATCH] Kbuild: Move -Wmaybe-uninitialized to W=1

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Date:	Thu, 28 Jul 2016 22:28:14 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Borislav Petkov <bp@...en8.de>, Sam Ravnborg <sam@...nborg.org>,
	lkml <linux-kernel@...r.kernel.org>, Michael Matz <matz@...e.de>,
	Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
	x86-ml <x86@...nel.org>
Subject: Re: [PATCH] Kbuild: Move -Wmaybe-uninitialized to W=1


* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> On Thu, Jul 28, 2016 at 12:03 PM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> >
> > Once we get to the point that the warning is no longer useful, and is more 
> > pain than gain, it gets disabled.
> 
> Btw, I have a suspicion that you didn't realize that "-Wmaybe-uninitialized" is 
> separate from "-Wuninitialized" (which is *not* disabled).

I very much know the difference, as you can see from the commit IDs I cited.

> The "maybe-uninitialized" warning is literally gcc saying "I haven't really 
> followed all the logic, but from my broken understanding it isn't _obvious_ that 
> it is initialized".
> 
> And the problem is that a lot of gcc optimization choices basically move the 
> pointer of "obvious". So the warning is a bit random to begin with. And when the 
> gcc people screw thigns up, things go to hell in a handbasket.

Fair enough.

Thanks,

	Ingo