Re: + mm-mmapc-replace-find_vma_prepare-with-clearer-find_vma_links.patch added to -mm tree

[Hugh Dickins <hughd@google.com>]

On Tue, 11 Sep 2012, David Rientjes wrote:
> On Thu, 16 Aug 2012, akpm@linux-foundation.org wrote:
> > 
> > This does revert 2.6.27's dfe195fb79e88 ("mm: fix uninitialized variables
> > for find_vma_prepare callers"), but it looks like gcc 4.3.0 was one of
> > those releases too eager to shout about uninitialized variables: only
> > copy_vma() warns with 4.5.1 and 4.7.1, which a BUG on error silences.
> > 
> 
> That trick doesn't work if CONFIG_BUG=n.
> 
> mm/mmap.c: In function 'copy_vma':
> mm/mmap.c:2344: warning: 'prev' may be used uninitialized in this function
> mm/mmap.c:2345: warning: 'rb_link' may be used uninitialized in this function
> mm/mmap.c:2345: warning: 'rb_parent' may be used uninitialized in this function

Hmm, right: not an option I ever choose, and I hadn't given it a thought.

But do we care?  If this introduced the only such warning, I would care.
But that seems to be far from the case - building my usual config without
CONFIG_BUG gives me 36 warnings, of uninitialized and unused and
control reaches end of non-void varieties.

Hugh