This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: odd array subscript is above array bounds error
On Thu, Mar 05, 2009 at 10:05:15AM +0100, Manuel López-Ibáñez wrote:
> 2009/3/5 Dave Korn <dave.korn.cygwin@googlemail.com>:
> >
> > of an array that only has size[4] is going one past the end. ?So the bug is
> > the missing warning for the simplified testcase, not that the warning is
> > somehow incorrect in the more complex one.
>
> No. The array is unused so it gets removed quite early. If you *do*
> return the array, then the warning appears. There is no bug here
> (except we could warn for unused array, that would be nice... if you
> wish to open a PR for that).
>
> > ?I would hope that in the simpler case the entire unused local array gets
> > optimised away, and the loop and 'a' go with it. ?That might explain why
> > there's no sign of an error. ?But your testcase invokes invalid behaviour, so
> > there's no reason why the compiler shouldn't handle it in differing and
> > inconsistent ways at different optimisation levels.
>
> In fact the simple local array gets removed by the moment we reach 034t.sdse.
>
> Cheers,
>
> Manuel.
Manuel,
It seems that the simplier testcase must be optimizing away the loop
at all optimization levels. Are there any options that would suppress that
optimization if one was just looking for array bounds errors with -Warray-bounds?
Jack