linux-kernel - Re: [GIT PULL 2/2] Kconfig updates for v5.10-rc1

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Message-ID: <CAHk-=whK0aQxs6Q5ijJmYF1n2ch8cVFSUzU5yUM_HOjig=+vnw@mail.gmail.com>
Date:   Sat, 28 Nov 2020 10:28:31 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Emese Revfy <re.emese@...il.com>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [GIT PULL 2/2] Kconfig updates for v5.10-rc1

On Fri, Nov 27, 2020 at 11:05 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> As for the cc1plus cost, I got a similar result.
>
> Running scripts/gcc-plugin.sh directly
> took me 0.5 sec, which is a fourth
> of the allmodconfig run-time.
>
> Actually, I did not know this shell script
> was so expensive to run...

So it turns out that one reason it's so expensive to run is that it
does a *lot* more than it claims to do.

It says "we need a c++ compiler that supports the designated
initializer GNU extension", but then it actually includes a header
file from hell, rather than just test designated initializers.

This patch makes the cc1plus overhead go down a lot. That said, I'm
doubtful we really want gcc plugins at all, considering that the only
real users have all apparently migrated to clang builtin functionality
instead.

        Linus

View attachment "patch.diff" of type "text/x-patch" (634 bytes)