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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri, 21 Aug 2020 11:02:08 -0700
Message-ID: <CAHk-=whjVCTjZG0Y88WhJruLdbxF=7q3mmFThD+N5WK0P5giSw@mail.gmail.com>
Subject: Re: [PATCH 0/4] -ffreestanding/-fno-builtin-* patches
To:     Arvind Sankar <nivedita@alum.mit.edu>
Cc:     Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Nick Desaulniers <ndesaulniers@google.com>,
        =?UTF-8?B?RMOhdmlkIEJvbHZhbnNrw70=?= <david.bolvansky@gmail.com>,
        Eli Friedman <efriedma@quicinc.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Michal Marek <michal.lkml@markovi.net>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
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        Dmitry Vyukov <dvyukov@google.com>,
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        Daniel Axtens <dja@axtens.net>,
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        Yury Norov <yury.norov@gmail.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@kernel.org>,
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        Daniel Kiper <daniel.kiper@oracle.com>,
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On Fri, Aug 21, 2020 at 10:54 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Fri, Aug 21, 2020 at 10:29 AM Arvind Sankar <nivedita@alum.mit.edu> wrote:
> >
> > This is why I'm saying clang's no-builtin-foo option is useful for
> > embedded: it doesn't prevent the programmer using __builtin_foo(), it
> > prevents the _compiler_ using __builtin_foo() on its own.
>
> And that's fine. But it's apparently not what gcc does.

Oh, testing it seems to say that that is exactly what gcc does too. I
must have misunderstood some comment in this thread to mean otherwise.

                Linus