On Wed, Feb 3, 2021 at 2:24 PM Masahiro Yamada [off-list ref] wrote:

On Sat, Jan 30, 2021 at 10:52 AM Nathan Chancellor [off-list ref] wrote:

quoted

On Fri, Jan 29, 2021 at 04:44:00PM -0800, Nick Desaulniers wrote:

quoted

Modifies CONFIG_DEBUG_INFO_DWARF4 to be a member of a choice which is
the default. Does so in a way that's forward compatible with existing
configs, and makes adding future versions more straightforward.

GCC since ~4.8 has defaulted to this DWARF version implicitly.

Suggested-by: Arvind Sankar <redacted>
Suggested-by: Fangrui Song <redacted>
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Nick Desaulniers <redacted>

One comment below:

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

quoted

---
 Makefile          |  5 ++---
 lib/Kconfig.debug | 16 +++++++++++-----
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/Makefile b/Makefile
index 95ab9856f357..d2b4980807e0 100644
--- a/Makefile
+++ b/Makefile

@@ -830,9 +830,8 @@ ifneq ($(LLVM_IAS),1)
 KBUILD_AFLAGS        += -Wa,-gdwarf-2

It is probably worth a comment somewhere that assembly files will still
have DWARF v2.

I agree.
Please noting the reason will be helpful.

Via a comment in the source, or in the commit message?

Could you summarize Jakub's comment in short?
https://patchwork.kernel.org/project/linux-kbuild/patch/20201022012106.1875129-1-ndesaulniers@google.com/#23727667

Via a comment in the source, or in the commit message?

One more question.


Can we remove -g option like follows?


 ifdef CONFIG_DEBUG_INFO_SPLIT
 DEBUG_CFLAGS   += -gsplit-dwarf
-else
-DEBUG_CFLAGS   += -g
 endif





In the current mainline code,
-g is the only debug option
if CONFIG_DEBUG_INFO_DWARF4 is disabled.


The GCC manual says:
https://gcc.gnu.org/onlinedocs/gcc-10.2.0/gcc/Debugging-Options.html#Debugging-Options


-g

    Produce debugging information in the operating system’s
    native format (stabs, COFF, XCOFF, or DWARF).
    GDB can work with this debugging information.


Of course, we expect the -g option will produce
the debug info in the DWARF format.





With this patch set applied, it is very explicit.

Only the format type, but also the version.

The compiler will be given either
-gdwarf-4 or -gdwarf-5,
making the -g option redundant, I think.

Can I provide that as a separate patch?  I don't want any breakage
from that to delay DWARF v5 support further.  If so, should it be the
first patch or last?
-- 
Thanks,
~Nick Desaulniers