linux-toolchains.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Florian Weimer <fweimer@redhat.com>
To: Linus Torvalds <torvalds@linuxfoundation.org>
Cc: Segher Boessenkool <segher@kernel.crashing.org>,
	Nathan Chancellor <nathan@kernel.org>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	llvm@lists.linux.dev, linux-toolchains@vger.kernel.org
Subject: Re: [GIT PULL v2] Kbuild updates for v5.15-rc1
Date: Mon, 06 Sep 2021 20:27:25 +0200	[thread overview]
Message-ID: <87lf49wodu.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <CAHk-=wh0MBVfA89WLWnCiSnJ2a=hSAoSxfG-jyf7JJeBDPK3ew@mail.gmail.com> (Linus Torvalds's message of "Mon, 6 Sep 2021 11:11:35 -0700")

* Linus Torvalds:

> We use the compiler intrinsics without the C library header files for
> everything else, so doing so for <stdarg.h> seems to actually be a
> clarification and improvement.

This is an exaggeration.  On several architectures, the kernel cannot
use the vector built-ins directly.  Some of the implementing headers are
very special and intertwined with the compiler.  <stdarg.h> is currently
not such a case, but it's just not technically not feasible to avoid
dependencies on all compiler headers.  I think this considerably weakens
the case against <stdarg.h> because the compiler version is so obviously
harmless.

What the kernel is doing here is imposing an unnecesary constraint on
compiler development.  Basically, you are telling compiler writers that
implementing features with the help of header files is a bad idea
because it makes it more difficult to use them from the kernel.  (See
the proposed exceptions for vector code.)

Thanks,
Florian


  reply	other threads:[~2021-09-06 18:28 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CAK7LNAQ0Q6CdXaD-dVGj_e3O3JYs_crpejWKpXHYQJYxyk-1VQ@mail.gmail.com>
     [not found] ` <CAHk-=wgoX0pVqNMMOcrhq=nuOfoZB_3qihyHB3y1S8qo=MDs6w@mail.gmail.com>
2021-09-03 23:04   ` [GIT PULL v2] Kbuild updates for v5.15-rc1 Nathan Chancellor
2021-09-04  8:01     ` Florian Weimer
2021-09-04 13:19       ` Segher Boessenkool
2021-09-04 15:19         ` Florian Weimer
2021-09-04 16:19           ` Segher Boessenkool
2021-09-04 17:22           ` Linus Torvalds
2021-09-04 19:15             ` Segher Boessenkool
2021-09-04 19:58               ` Linus Torvalds
2021-09-06 15:46                 ` Segher Boessenkool
2021-09-06 16:30                   ` Linus Torvalds
2021-09-06 17:27                     ` Segher Boessenkool
2021-09-06 18:11                       ` Linus Torvalds
2021-09-06 18:27                         ` Florian Weimer [this message]
2021-09-06 19:48                           ` Segher Boessenkool
2021-09-06 20:14                             ` Jakub Jelinek
2021-09-06 21:08                               ` Linus Torvalds
2021-09-06 21:24                                 ` Linus Torvalds
2021-09-07 14:41                                   ` Segher Boessenkool
2021-09-06 21:52                                 ` Jakub Jelinek
2021-09-06 22:24                                   ` Linus Torvalds
2021-09-07 15:26                                     ` Segher Boessenkool
2021-09-07 14:52                                   ` Segher Boessenkool
2021-09-09  5:14                                     ` Masahiro Yamada
2021-09-07 14:29                                 ` Segher Boessenkool
2021-09-06  6:54             ` Florian Weimer
2021-09-06 16:02               ` Alexey Dobriyan
2021-09-08  3:09                 ` Masahiro Yamada

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=87lf49wodu.fsf@oldenburg.str.redhat.com \
    --to=fweimer@redhat.com \
    --cc=clang-built-linux@googlegroups.com \
    --cc=linux-kbuild@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-toolchains@vger.kernel.org \
    --cc=llvm@lists.linux.dev \
    --cc=masahiroy@kernel.org \
    --cc=nathan@kernel.org \
    --cc=ndesaulniers@google.com \
    --cc=segher@kernel.crashing.org \
    --cc=torvalds@linuxfoundation.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).