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

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Message-ID: <CAHk-=wjsbYJuO=3331LmQGePXWAdHEdT33HOup53shjMJFan6Q@mail.gmail.com>
Date:   Wed, 19 Oct 2022 17:10:54 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Segher Boessenkool <segher@...nel.crashing.org>,
        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>,
        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

On Wed, Oct 19, 2022 at 1:35 PM Jason A. Donenfeld <Jason@...c4.com> wrote:
>
> I wish folks would use `u8 *` when they mean "byte array".

Together with '-funsigned-char', we could typedef 'u8' to just 'char'
(just for __KERNEL__ code, though!), and then we really could just use
'strlen()' and friends on said kind of arrays without any warnings.

But we do have a *lot* of 'unsigned char' users, so it would be a huge
amount of churn to do this kind of thing.

And as mentioned, right now we definitely have a lot of other "ignore
sign" code.

Much of it is probably simply because we haven't been able to ever use
that warning flag, so it's just accumulated and might be trivial to
fix. But I wouldn't be surprised at all if some of it ends up somewhat
fundamental.

              Linus