From mboxrd@z Thu Jan  1 00:00:00 1970
From: slash.tmp@free.fr (Mason)
Date: Fri, 31 Jul 2015 10:28:03 +0200
Subject: arch/arm/kernel/setup.c does not compile at -O0
In-Reply-To: <55BA4C4B.3070705@free.fr>
References: <55BA1E62.9080103@free.fr> <55BA2335.706@arm.com>
 <55BA2D9D.1070402@free.fr> <55BA4C4B.3070705@free.fr>
Message-ID: <55BB3193.9080007@free.fr>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 30/07/2015 18:09, Mason wrote:

> It appears that "gcc -g" and "gcc -gdwarf-2 -g" generate different
> debugging information... What debugging format does "gcc -g" use?

For the sake of completeness.

My compiler:
gcc version 4.9.3 20141031 (prerelease) (Linaro GCC 2014.11)

-gdwarf-2 generates DWARF 2
-gdwarf-3 generates DWARF 3
-g generates DWARF 4

It seems that my aging version of DS-5
"ARM DS-5 Development Studio version 5.13 build 1622" dated 2012/12/14
did NOT support DWARF 4 debug format...
(at least not the DWARF 4 generated by gcc 4.9.3)

which is weird because the changelog for 5.12 states:
"Support for DWARF4 debug information generated by gcc 4.5 releases"

> I'm now using this patch locally:
> 
> $ git diff Makefile
> diff --git a/Makefile b/Makefile
> index f9041e6d4d19..f79c480f8922 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -641,10 +641,8 @@ KBUILD_CFLAGS      += -fomit-frame-pointer
>  endif
>  endif
>  
> -KBUILD_CFLAGS   += $(call cc-option, -fno-var-tracking-assignments)
> -
>  ifdef CONFIG_DEBUG_INFO
> -KBUILD_CFLAGS  += -g
> +KBUILD_CFLAGS  += -gdwarf-3
>  KBUILD_AFLAGS  += -Wa,--gdwarf-2
>  endif

Regards.