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

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Date:   Mon,  3 Oct 2022 03:11:06 +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>,
        Tom Rix <trix@...hat.com>, llvm@...ts.linux.dev
Subject: [PATCH 2/3] Kconfig.debug: add toolchain checks for DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT

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@...nel.org>
---

 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