linux-kernel - [PATCH v2 2/3] Kconfig.debug: add toolchain checks for DEBUG_INFO_DWARF_TOOLCHAIN

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Message-Id: <20221004162905.24997-2-masahiroy@kernel.org>
Date:   Wed,  5 Oct 2022 01:29:04 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     linux-kbuild@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>
Subject: [PATCH v2 2/3] Kconfig.debug: add toolchain checks for DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT

CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT does not give explicit
-gdwarf-* flag. 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 tricky, but at least, the -g flag
works for Clang <=13, which defaults to DWARF v4.

Clang 14 switched its default to DWARF v5.

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

(no changes since v1)

 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