linux-kernel - Re: [PATCH v2 2/3] Kconfig.debug: add toolchain checks for DEBUG_INFO_DWARF_TOOLCHAIN

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Date:   Thu, 13 Oct 2022 02:03:07 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     linux-kbuild@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <nathan@...nel.org>
Subject: Re: [PATCH v2 2/3] Kconfig.debug: add toolchain checks for DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT

On Wed, Oct 5, 2022 at 1:30 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT does not give explicit
> -gdwarf-* flag. The actual DWARF version is up to the toolchain.
>
> The combination of GCC and GAS works fine, and Clang with the integrated
> assembler is good too.
>
> The combination of Clang and GAS is tricky, but at least, the -g flag
> works for Clang <=13, which defaults to DWARF v4.
>
> Clang 14 switched its default to DWARF v5.
>
> Now, CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT has the same issue as
> addressed by commit 98cd6f521f10 ("Kconfig: allow explicit opt in to
> DWARF v5").
>
> CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y for Clang >= 14 and
> GAS < 2.35 produces a ton of errors like follows:
>
>   /tmp/main-c2741c.s: Assembler messages:
>   /tmp/main-c2741c.s:109: Error: junk at end of line, first unrecognized character is `"'
>   /tmp/main-c2741c.s:109: Error: file number less than one
>
> Add 'depends on' to check toolchains.
>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> Reviewed-by: Nathan Chancellor <nathan@...nel.org>
> ---

Applied to linux-kbuild.



> (no changes since v1)
>
>  lib/Kconfig.debug | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index f4b2165f24db..cc90414d492e 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -253,6 +253,7 @@ config DEBUG_INFO_NONE
>  config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
>         bool "Rely on the toolchain's implicit default DWARF version"
>         select DEBUG_INFO
> +       depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502)
>         help
>           The implicit default version of DWARF debug info produced by a
>           toolchain changes over time.
> --
> 2.34.1
>


-- 
Best Regards
Masahiro Yamada