Re: [PATCH/middle-end/diagnostic] Do not warn about unused out of bounds array refs

["Richard Guenther" <richard dot guenther at gmail dot com>]

On 3/20/07, Jakub Jelinek <jakub@redhat.com> wrote:
> On Tue, Mar 20, 2007 at 05:32:59PM +0100, Dirk Mueller wrote:
> > On Tuesday, 20. March 2007, Richard Guenther wrote:
> >
> > > I still would prefer you'd warn at dereference or escape sites only
> > > (escape sites
> > > are possible dereference sites).
> >
> > That would disable warnings about taking addresses of array references that
> > are out of bounds. Right?
>
> If you never dereference such a pointer and it doesn't escape.
>
> char a[10];
> char *r;
>
> int foo (void)
> {
>   char *p = &a[12];     // This wouldn't warn
>   char *q = &a[12];
>   *q = 5;               // We would warn here
>   r = &a[-1];           // and here as well
>   bar ();
> }
>
> But if you never dereference it and it doesn't escape, then it is completely
> harmless.

Yes, and in most cases (as above) the address taking would be removed by DCE
anyway.

Richard.

> As is -Warray-bounds just causes too many false positives, see
> PR31227 or e.g. yesterday when I tried to bootstrap with obj-c++
> among --enable-languages trunk didn't bootstrap because of it either.
>
>         Jakub