On 2021-01-15, Nick Desaulniers wrote:
From: Masahiro Yamada <masahiroy@xxxxxxxxxx> 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]
The gas commit description has a typo. The supported options are -gdwarf-[345] or --gdwarf-[345]. -gdwarf2 and --gdwarf2 are kept for compatibility. Looks good otherwise.
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 Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> Reviewed-by: Nathan Chancellor <natechancellor@xxxxxxxxx> Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> --- 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
