linux-kernel - Re: [GIT PULL] kbuild updates for v4.7-rc1

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Date:	Thu, 26 May 2016 22:26:50 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Michal Marek <mmarek@...e.com>
Cc:	Arnd Bergmann <arnd@...db.de>, mussitantesmortem@...il.com,
	nicolas.ferre@...el.com, Nicolas Pitre <nicolas.pitre@...aro.org>,
	robert.jarzmik@...e.fr, yamada.masahiro@...ionext.com,
	Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] kbuild updates for v4.7-rc1

On Thu, May 26, 2016 at 1:33 PM, Michal Marek <mmarek@...e.com> wrote:
>
>   git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild.git kbuild

This pull results in new warnings.

I get new "may be uninitialized" warnings now for me allmodconfig
build, and while I didn't look at them all, the one I looked at was
just entirely crap:

   fs/gfs2/dir.c: In function ‘dir_split_leaf.isra.16’:
   fs/gfs2/dir.c:1021:8: warning: ‘leaf_no’ may be used uninitialized
in this function [-Wmaybe-uninitialized]
     error = get_leaf(dip, leaf_no, &obh);
           ^

yeah no, leaf_no is initialized a few lines up by

        error = get_leaf_nr(dip, index, &leaf_no);

and the fact that gcc can't follow the trivial  error handling is not
our fault. It looks *so* trivial that I wonder why.

That said, I don't see exactly what in the pull request causes this.

My reading of the diff seems to say that you are actually adding
*more* cases of -Wno-maybe-uninitialized, not less.

So I suspect it's almost accidental in just how the Kconfig option
CC_OPTIMIZE_FOR_PERFORMANCE happened, which in turn probably just
changes the options for "make allmiodconfig", and it now picks a
non-size-optimized build that always showed those warnings and I just
didn't see them.

Annoying. I've pulled it, but I wish you would look at this.

              Linus