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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sat, 23 Sep 2023 11:04:57 -0700
Message-ID: <CAHk-=whf6Zu3Cfm1eOTxXniZf5EPaf1iLj_q_6BVHrzTUBfUGw@mail.gmail.com>
Subject: Re: [GIT PULL] hardening fixes for v6.6-rc3
To:     Kees Cook <keescook@chromium.org>
Cc:     linux-kernel@vger.kernel.org,
        Alexey Dobriyan <adobriyan@gmail.com>,
        linux-hardening@vger.kernel.org
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On Fri, 22 Sept 2023 at 20:49, Kees Cook <keescook@chromium.org> wrote:
>
> 2) __cplusplus is relatively common in UAPI headers already:
>    $ git grep __cplusplus -- include/uapi | wc -l
>    58

Look a bit closer.

Most of those - by far - is for the usual

  #if defined(__cplusplus)
  extern "C" {
  #endif

pattern. IOW, it's explicitly not different code, but telling the C++
compiler that "this is C code".

So this new #ifdef is an ugly new pattern of "do totally different
things for C++".

Apparently required, but very ugly nonetheless.

               Linus