Re: [PATCH 1/1] mmap: fix uninitialized entities warnings.

[Matthew Wilcox <matthew@wil.cx>]

On Thu, May 01, 2008 at 11:40:37PM +0300, Adrian Bunk wrote:
> On Thu, May 01, 2008 at 02:25:33PM -0600, Matthew Wilcox wrote:
> > However, the code is not buggy.  Just compare:
> > 
> >                         vma = vma_tmp;
> >                         if (vma_tmp->vm_start <= addr)
> >                                 return vma;
> > 
> > with
> > 
> > munmap_back:
> >         vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
> >         if (vma && vma->vm_start < addr + len) {
> >                 if (do_munmap(mm, addr, len))
> >                         return -ENOMEM;
> >                 goto munmap_back;
> >         }
> > 
> > Now, we know that addr + len does not wrap, and that len > 0, so we know
> > that this warning is incorrect.  But it's not reasonable to expect gcc to
> > be able to deduce this.
> >...
> 
> Can you submit a patch with your explanation that uses 
> uninitialized_var() to silence these warnings?

I could, but I don't know if I want to.  Suppose somebody changes the
code later to actually make prev used before it's initialised?  Then we
would have GCC not warning about a problem.

-- 
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