linux-kernel - Re: [PATCH] kbuild: add option to set max level of debug info

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Date:   Thu, 11 Aug 2022 14:58:28 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Dmitrii Bundin <dmitrii.bundin.a@...il.com>
Cc:     masahiroy@...nel.org, michal.lkml@...kovi.net,
        ndesaulniers@...gle.com, nathan@...nel.org, peterz@...radead.org,
        keescook@...omium.org, jpoimboe@...nel.org,
        dan.j.williams@...el.com, isabbasso@...eup.net,
        edumazet@...gle.com, vbabka@...e.cz, linux@...musvillemoes.dk,
        linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org
Subject: Re: [PATCH] kbuild: add option to set max level of debug info

On Fri,  5 Aug 2022 01:35:04 +0300 Dmitrii Bundin <dmitrii.bundin.a@...il.com> wrote:

> When compiling with -g3 option and debugging with gdb it provides some
> extra abilities like macro expand, info macro etc... It's sometimes
> useful to unerstand behavior of complicated macros.
> 
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -304,6 +304,15 @@ config DEBUG_INFO_REDUCED
>  	  DEBUG_INFO build and compile times are reduced too.
>  	  Only works with newer gcc versions.
>  
> +config DEBUG_INFO_MAXLEVEL
> +	bool "Maximum debug information level"
> +	depends on !DEBUG_INFO_REDUCED
> +	default n
> +	help
> +	  Sets the maximum level of debug information compilers may generate
> +	  (-g3). Enabling this option will require significantly more disk space
> +	  and increase built time, but it's useful for debugging purposes.
> +
>  config DEBUG_INFO_COMPRESSED
>  	bool "Compressed debugging information"
>  	depends on $(cc-option,-gz=zlib)
> diff --git a/scripts/Makefile.debug b/scripts/Makefile.debug
> index 9f39b0130551..7e1d8beecfc4 100644
> --- a/scripts/Makefile.debug
> +++ b/scripts/Makefile.debug
> @@ -2,6 +2,8 @@ DEBUG_CFLAGS	:=
>  
>  ifdef CONFIG_DEBUG_INFO_SPLIT
>  DEBUG_CFLAGS	+= -gsplit-dwarf
> +else ifdef CONFIG_DEBUG_INFO_MAXLEVEL
> +DEBUG_CFLAGS	+= -g3
>  else
>  DEBUG_CFLAGS	+= -g
>  endif

What happens when the gcc developers add -g4?  Or if a user wants -g2?

In other words, can we make this a Kconfig-selectable level, with the
default `1'?