Re: [PATCH 5/6] kbuild: rust_is_available: fix confusion when a version appears in the path

[Masahiro Yamada]

On Sat, Jan 14, 2023 at 8:13 AM Miguel Ojeda
<miguel.ojeda.sandonis@xxxxxxxxx> wrote:
>
> On Thu, Jan 12, 2023 at 6:32 AM Masahiro Yamada <masahiroy@xxxxxxxxxx> 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