Re: [PATCH] -Walloca-larger-than with constant sizes at -O0 (PR 100425)

[Richard Biener <richard.guenther@gmail.com>]

On Wed, May 5, 2021 at 4:20 AM Martin Sebor via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Even when explicitly enabled, -Walloca-larger-than doesn't run
> unless optimization is enabled as well.  This prevents diagnosing
> alloca calls with constant arguments in excess of the limit that
> could otherwise be flagged even at -O0, making the warning less
> consistent and less useful than is possible.
>
> The attached patch enables -Walloca-larger-than for calls with
> constant arguments in excess of the limit even at -O0 (variable
> arguments are only handled with optimization, when VRP runs).

Hmm, but then the pass runs even without -Walloca or -Walloca-larger-than
or -Wvla[-larger-than].  It performs an IL walk we should avoid in those
cases.

So the patch is OK but can you please come up with a gate that disables
the pass when all of the warnings it handles won't fire anyway?

Thanks,
Richard.

> Martin