Re: [PATCH 2/2] Kbuild: Add a option to enable dwarf4

Sam Ravnborg
2014-07-20T19:23:19Z

On Wed, Jul 16, 2014 at 01:16:12AM +0200, Andi Kleen wrote:
> From: Andi Kleen <ak@linux.intel.com>
>
> I found that a lot of unresolvable variables when using gdb on the kernel
> become resolvable when dwarf4 is enabled. So add a Kconfig flag to enable it.
>
> It definitely increases the debug information size, but on the other
> hand this isn't so bad when debug fusion is used.

Would it not make sense to try to enable degug info like this:
First try -gdwarf-4
If this fails try -gdwarf-3
If this fails try -gdwarf-2
And if this also fails fallback to -g

We could then us a Kconfig option to enable the highest debug level - where 4 for now is the highest.
On the other hand if most people have revent utils then they all have -gdwarf-4 supported
and then it is no big deal.

Sam

>
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> ---
> Makefile | 3 +++
> lib/Kconfig.debug | 9 +++++++++
> 2 files changed, 12 insertions(+)
>
> diff --git a/Makefile b/Makefile
> index 953659e..9c4080b 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -690,6 +690,9 @@ KBUILD_CFLAGS += -g
> KBUILD_AFLAGS += -Wa,-gdwarf-2
> endif
> endif
> +ifdef CONFIG_DEBUG_INFO_DWARF4
> +KBUILD_CFLAGS += -gdwarf-4
> +endif
Should we sue $(call cc-option ...) here as not all gcc's supports this today?

Sam