linux-kernel - Re: [PATCH v3] kbuild: add debug level and macro defs options

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Message-ID: <CANXV_XzGHQ8_X2t37DwRjS7kKFX0kWDpwHEg3k+zZ4YfV98gjw@mail.gmail.com>
Date:   Thu, 18 Aug 2022 21:57:02 +0300
From:   Dmitrii Bundin <dmitrii.bundin.a@...il.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Isabella Basso <isabbasso@...eup.net>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        F���ng-ru��� S���ng 
        <maskray@...gle.com>, Michal Marek <michal.lkml@...kovi.net>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH v3] kbuild: add debug level and macro defs options

On Thu, Aug 18, 2022 at 7:14 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> -g1 is only possible via DEBUG_INFO_LEVEL, but
> presumably it is not your main interest
> (and not sure if there is anybody interested)
> because the main motivation for your v1
> is to generate macro debug data.

I tested the build process with -g1 and it turned out to generate an
image that is 20% lesser in size.
This is indeed not really my use-case, but are you sure it might not
be helpful in general?

The reason to add DEBUG_INFO_LEVEL was also motivated by the
GCC11+/Clang12+ behavior of -gsplit-dwarf to provide an orthogonal
debug level config.
"The later -g<level> wins" behavior in turns works identically for
both older and newer compiler versions so such an implementation
provides version independent build behavior.
Testing on gcc-11, -gdwarf-<level>/-gdwarf still implies -g2.
It seemed a clearer way to me to explicitly set a debug level that
just wins instead of relying on implicits.

Regards
Dmitrii