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

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Date:   Fri, 12 Aug 2022 03:33:29 +0300
From:   Dmitrii Bundin <dmitrii.bundin.a@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
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

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

Thanks for pointing this out.

Here is a little note from my side. According to the GCC documentation
the default level is 2. So I would propose to set the default Kconfig
option value to 2 as well to not change the build behavior.

Does this sound reasonable?

Regards,
Dmitrii
On Fri, Aug 12, 2022 at 12:58 AM Andrew Morton
<akpm@...ux-foundation.org> wrote:
>
> 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'?