Messages in this thread Patch in this message | | | Date | Tue, 12 Jan 2021 16:32:33 -0800 | Subject | [PATCH v4 1/3] Remove $(cc-option,-gdwarf-4) dependency from CONFIG_DEBUG_INFO_DWARF4 | From | Nick Desaulniers <> |
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From: Masahiro Yamada <masahiroy@kernel.org>
The -gdwarf-4 flag is supported by GCC 4.5+, and also by Clang.
You can see it at https://godbolt.org/z/6ed1oW
For gcc 4.5.3 pane, line 37: .value 0x4 For clang 10.0.1 pane, line 117: .short 4
Given Documentation/process/changes.rst stating GCC 4.9 is the minimal version, this cc-option is unneeded.
Note ----
CONFIG_DEBUG_INFO_DWARF4 controls the DWARF version only for C files.
As you can see in the top Makefile, -gdwarf-4 is only passed to CFLAGS.
ifdef CONFIG_DEBUG_INFO_DWARF4 DEBUG_CFLAGS += -gdwarf-4 endif
This flag is used when compiling *.c files.
On the other hand, the assembler is always given -gdwarf-2.
KBUILD_AFLAGS += -Wa,-gdwarf-2
Hence, the debug info that comes from *.S files is always DWARF v2. This is simply because GAS supported only -gdwarf-2 for a long time.
Recently, GAS gained the support for --dwarf-[3|4|5] options. [1] And, also we have Clang integrated assembler. So, the debug info for *.S files might be improved if we want.
In my understanding, the current code is intentional, not a bug.
[1] https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=31bf18645d98b4d3d7357353be840e320649a67d
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> --- lib/Kconfig.debug | 1 - 1 file changed, 1 deletion(-)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 78361f0abe3a..dd7d8d35b2a5 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -258,7 +258,6 @@ config DEBUG_INFO_SPLIT config DEBUG_INFO_DWARF4 bool "Generate dwarf4 debuginfo" - depends on $(cc-option,-gdwarf-4) help Generate dwarf4 debug info. This requires recent versions of gcc and gdb. It makes the debug information larger. -- 2.30.0.284.gd98b1dd5eaa7-goog
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