linux-kernel - Re: [PATCH] kbuild: treat char as always signed

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Date:   Wed, 19 Oct 2022 14:23:01 -0600
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-toolchains@...r.kernel.org,
        Masahiro Yamada <masahiroy@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] kbuild: treat char as always signed

Hi Linus,

On Wed, Oct 19, 2022 at 12:54:06PM -0700, Linus Torvalds wrote:
> On Wed, Oct 19, 2022 at 9:27 AM Jason A. Donenfeld <Jason@...c4.com> wrote:
> >
> > So let's just eliminate this particular variety of heisensigned bugs
> > entirely. Set `-fsigned-char` globally, so that gcc makes the type
> > signed on all architectures.
> 
> Btw, I do wonder if we might actually be better off doing this - but
> doing it the other way around.

That could work. The argument here would be that most people indeed
treat char as a byte. I'll send a v2 doing this.

This will probably break some things, though, on drivers that are
already broken on e.g. ARM. For example, the wifi driver I fixed that
started this whole thing would now be broken on x86 too. But also, we're
barely past rc1, so maybe this is something to do now, and then we'll
spend the rest of the 6.1 cycle fixing issues as the pop up? Sounds fine
to me if you think that's doable.

Either way, I'll send a patch and you can do with it what you think is
best.

Jason