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From:   Arvind Sankar <nivedita@alum.mit.edu>
Date:   Wed, 10 Jun 2020 00:26:24 -0400
To:     Arvind Sankar <nivedita@alum.mit.edu>
Cc:     Rong Chen <rong.a.chen@intel.com>,
        Fangrui Song <maskray@google.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        kernel test robot <lkp@intel.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        kbuild-all@lists.01.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [kbuild-all] Re: gcc-5: error: -gz is not supported in this
 configuration
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On Tue, Jun 09, 2020 at 11:23:31PM -0400, Arvind Sankar wrote:
> On Tue, Jun 09, 2020 at 11:12:25PM -0400, Arvind Sankar wrote:
> > The output of gcc-5 -dumpspecs may also be useful.
> > 
> > The exact Kconfig check should have been
> > 	gcc-5 -Werror -gz=zlib -S -x c /dev/null -o /dev/null
> > 
> > I can't see how that would succeed if the a.c test didn't but maybe just
> > in case?
> 
> Oh wait, -S instead of -c. Which means it runs neither the assembler nor
> the linker, so gcc won't error out. But if that gcc was originally
> _configured_ with a version of binutils that doesn't support -gz=zlib,
> it will give an error on -c regardless of whether the runtime binutils
> would actually support it or not.

I think the below might be better than passing the option via -Wa, since
gcc will translate -gz=zlib into the right assembler option anyway, and
it will also generate an error if the compiler driver was misconfigured
and won't support the option even if the rest of the toolchain does,
fixing the config dependency.

Unless this doesn't work with Clang?

Alternatively (or even in addition), we should redefine cc-option to use
-c, it uses -S in the Kconfig version, apparently for speed, but -c in
the Kbuild version.

diff --git a/Makefile b/Makefile
index 839f9fee22cb..cb29e56f227a 100644
--- a/Makefile
+++ b/Makefile
@@ -842,7 +842,7 @@ endif
 
 ifdef CONFIG_DEBUG_INFO_COMPRESSED
 DEBUG_CFLAGS	+= -gz=zlib
-KBUILD_AFLAGS	+= -Wa,--compress-debug-sections=zlib
+KBUILD_AFLAGS	+= -gz=zlib
 KBUILD_LDFLAGS	+= --compress-debug-sections=zlib
 endif
 
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index cb98741601bd..94ce36be470c 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -229,7 +229,7 @@ config DEBUG_INFO_COMPRESSED
 	bool "Compressed debugging information"
 	depends on DEBUG_INFO
 	depends on $(cc-option,-gz=zlib)
-	depends on $(as-option,-Wa$(comma)--compress-debug-sections=zlib)
+	depends on $(as-option,-gz=zlib)
 	depends on $(ld-option,--compress-debug-sections=zlib)
 	help
 	  Compress the debug information using zlib.  Requires GCC 5.0+ or Clang