On Mon, Oct 03, 2022 at 03:11:06AM +0900, Masahiro Yamada wrote:
> CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT passes the -g option to the
> command line. The actual DWARF version is up to the toolchain.
>
> The combination of GCC and GAS works fine, and Clang with the integrated
> assembler is good too.
>
> The combination of Clang and GAS is a bit tricky, but at least, the
> default -g flag worked until LLVM 14 was released because Clang <=13
> defaults to DWARF v4.
>
> Clang 14 switched to DWARF v5 by default.
>
> Now, CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT has the same issue as
> addressed by commit 98cd6f521f10 ("Kconfig: allow explicit opt in to
> DWARF v5").
>
> CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y for Clang >= 14 and
> GAS < 2.35 produces a ton of errors like follows:
>
> /tmp/main-c2741c.s: Assembler messages:
> /tmp/main-c2741c.s:109: Error: junk at end of line, first unrecognized character is `"'
> /tmp/main-c2741c.s:109: Error: file number less than one
>
> Add 'depends on' to check toolchains.
>
> Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
> ---
>
> lib/Kconfig.debug | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index f4b2165f24db..cc90414d492e 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -253,6 +253,7 @@ config DEBUG_INFO_NONE
> config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
> bool "Rely on the toolchain's implicit default DWARF version"
> select DEBUG_INFO
> + depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502)
> help
> The implicit default version of DWARF debug info produced by a
> toolchain changes over time.
> --
> 2.34.1
>
>
Could we do something like this instead? Bikeshed the configuration
names as much as you want but we are duplicating most of this
conditional in a few different places so it would be good to consolidate
those in my opinion. Even though the DWARF4 and DWARF5 conditions are
the same, they might diverge so I think it makes sense to keep them
separate.
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index cc90414d492e..8e34a639cd40 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -231,6 +231,17 @@ config DEBUG_INFO
in the "Debug information" choice below, indicating that debug
information will be generated for build targets.
+config CC_AND_AS_SUPPORT_DWARF4
+ def_bool !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)
+
+config CC_AND_AS_SUPPORT_DWARF5
+ def_bool !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)
+
+config CC_AND_AS_SUPPORT_DWARF_DEFAULT
+ bool
+ default y if CC_AND_AS_SUPPORT_DWARF5 && (CLANG_VERSION >= 140000 || GCC_VERSION >= 110000)
+ default y if CC_AND_AS_SUPPORT_DWARF4 && (CLANG_VERSION < 140000 || GCC_VERSION < 110000)
+
choice
prompt "Debug information"
depends on DEBUG_KERNEL
@@ -253,7 +264,7 @@ config DEBUG_INFO_NONE
config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
bool "Rely on the toolchain's implicit default DWARF version"
select DEBUG_INFO
- depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502)
+ depends on CC_AND_AS_SUPPORT_DWARF_DEFAULT
help
The implicit default version of DWARF debug info produced by a
toolchain changes over time.
@@ -265,7 +276,7 @@ config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
config DEBUG_INFO_DWARF4
bool "Generate DWARF Version 4 debuginfo"
select DEBUG_INFO
- depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)
+ depends on CC_AND_AS_SUPPORT_DWARF4
help
Generate DWARF v4 debug info. This requires gcc 4.5+, binutils 2.35.2
if using clang without clang's integrated assembler, and gdb 7.0+.
@@ -277,7 +288,7 @@ config DEBUG_INFO_DWARF4
config DEBUG_INFO_DWARF5
bool "Generate DWARF Version 5 debuginfo"
select DEBUG_INFO
- depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)
+ depends on CC_AND_AS_SUPPORT_DWARF5
help
Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc
5.0+ accepts the -gdwarf-5 flag but only had partial support for some
