path: root/init
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authorMasahiro Yamada <masahiroy@kernel.org>2020-12-01 12:27:48 +0900
committerMasahiro Yamada <masahiroy@kernel.org>2021-02-12 05:11:20 +0900
commit83272e6d4765df775e43d5fc4797b4b3fe9a97fa (patch)
tree625f9ca4b46779109a8679b6da679597c6e73d3b /init
parentdb4632c65eb505410f2e6be9c4d50226c973a129 (diff)
kbuild: Remove $(cc-option,-gdwarf-4) dependency from DEBUG_INFO_DWARF4
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 --gdwarf-[345] options. [1] And, also we have Clang integrated assembler. So, the debug info for *.S files might be improved in the future. 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> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
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