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From:   Masahiro Yamada <masahiroy@kernel.org>
Date:   Sun, 15 Jan 2023 11:39:22 +0900
Message-ID: <CAK7LNAQo=w3F=VXNGYyo6-A4c8Sees6yVHrsaFXLknCrO0ET3Q@mail.gmail.com>
Subject: Re: [PATCH 5/6] kbuild: rust_is_available: fix confusion when a
 version appears in the path
To:     Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Cc:     Miguel Ojeda <ojeda@kernel.org>, linux-kbuild@vger.kernel.org,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Nicolas Schier <nicolas@fjasle.eu>,
        rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
        patches@lists.linux.dev, Alex Gaynor <alex.gaynor@gmail.com>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>
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On Sat, Jan 14, 2023 at 8:13 AM Miguel Ojeda
<miguel.ojeda.sandonis@gmail.com> wrote:
>
> On Thu, Jan 12, 2023 at 6:32 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
> >
> > +set -- ${bindgen_libclang_output#**clang version}
> > +bindgen_libclang_cversion=$(get_canonical_version $1)
> >  bindgen_libclang_min_version=$($min_tool_version llvm)
> > -bindgen_libclang_cversion=$(get_canonical_version $bindgen_libclang_version)
>
> Nice trick :) To be honest, I am not really fond of `set`, and in this
> case it means the command is not symmetric (we remove the prefix using
> parameter expansion, and the suffix via positional argument
> selection), but if you prefer it that way, I think it would be fine.


I just tend to write efficient code.
(scripts/{cc,ld,as}-version.sh do not use sed or grep at all.)

Especially, I avoid unneeded process forks
in the process forks.


> However, why the double asterisk? One already matches any string,
> including spaces, no?


Sorry, it is my mistake.

I meant double pound.


  set -- ${bindgen_libclang_output##*clang version}


The double pound strips "the longest matching pattern",
just in case "clang version" is contained in the file path.
(but if a space is contained in the directory path,
it would have failed earlier.


>
> Cheers,
> Miguel


--
Best Regards
Masahiro Yamada