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From:   Fangrui Song <maskray@google.com>
Date:   Fri, 26 May 2023 12:48:26 -0700
Message-ID: <CAFP8O3JO42CD2EXk+DJ5pci8ieHvRifAZpKg4iR_NiqTaYfLdA@mail.gmail.com>
Subject: Re: [PATCH v2] Compiler Attributes: Add __counted_by macro
To:     Kees Cook <keescook@chromium.org>
Cc:     Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>, ojeda@kernel.org,
        qing.zhao@oracle.com, morbo@google.com, llvm@lists.linux.dev,
        trix@redhat.com, linux-kernel@vger.kernel.org, nathan@kernel.org,
        linux-hardening@vger.kernel.org, gustavoars@kernel.org,
        ndesaulniers@google.com
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On Fri, May 26, 2023 at 11:56=E2=80=AFAM Kees Cook <keescook@chromium.org> =
wrote:
>
> On Fri, May 26, 2023 at 07:47:03PM +0200, Miguel Ojeda wrote:
> > On Fri, May 26, 2023 at 7:16=E2=80=AFPM Kees Cook <keescook@chromium.or=
g> wrote:
> > >
> > > FYI, applied to for-next/hardening:
> > >
> > > [1/1] Compiler Attributes: Add __counted_by macro
> > >       https://git.kernel.org/kees/c/86a76e91cbab
> >
> > Sorry, I was going to apply it soon -- in case you want it:
> >
> >     Acked-by: Miguel Ojeda <ojeda@kernel.org>
>
> Thanks!
>
> > And thanks Nathan for resubmitting the `Reviewed-by` from v1!
>
> Yes, apologies for missing this in my v2 submission!
>
> --
> Kees Cook
>

https://discourse.llvm.org/t/rfc-enforcing-bounds-safety-in-c-fbounds-safet=
y/70854
proposes a macro __counted_by as well.
This patch uses the same name:

> # define __counted_by(member)          __attribute__((__element_count__(m=
ember)))

I wonder whether the two use cases are compatible so that using the
same macro name will be fine.

#if defined(__has_feature) && __has_feature(bounds_safety)
#define __counted_by(T) __attribute__((__counted_by__(T)))
// ... other bounds annotations
#else
#define __counted_by(T) // defined as nothing // ... other bounds annotatio=
ns
#endif


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