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From:   Arvind Sankar <nivedita@alum.mit.edu>
Date:   Tue, 9 Jun 2020 23:12:25 -0400
To:     Rong Chen <rong.a.chen@intel.com>
Cc:     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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References: <202006092115.nevT7m8D%lkp@intel.com>
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On Wed, Jun 10, 2020 at 09:49:01AM +0800, Rong Chen wrote:
> 
> 
> On 6/10/20 8:58 AM, Fangrui Song wrote:
> > On 2020-06-10, Rong Chen wrote:
> >>
> >>
> >> On 6/10/20 1:49 AM, Fangrui Song wrote:
> >>> On 2020-06-09, Nick Desaulniers wrote:
> >>>> On Tue, Jun 9, 2020 at 6:12 AM kernel test robot <lkp@intel.com> 
> >>>> wrote:
> >>>>>
> >>>>> tree: 
> >>>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 
> >>>>> master
> >>>>> head:   abfbb29297c27e3f101f348dc9e467b0fe70f919
> >>>>> commit: 10e68b02c861ccf2b3adb59d3f0c10dc6b5e3ace Makefile: support 
> >>>>> compressed debug info
> >>>>> date:   12 days ago
> >>>>> config: x86_64-randconfig-r032-20200609 (attached as .config)
> >>>>> compiler: gcc-5 (Ubuntu 5.5.0-12ubuntu1) 5.5.0 20171010
> >>>>> reproduce (this is a W=1 build):
> >>>>>         git checkout 10e68b02c861ccf2b3adb59d3f0c10dc6b5e3ace
> >>>>>         # save the attached .config to linux build tree
> >>>>>         make W=1 ARCH=x86_64
> >>>>>
> >>>>> If you fix the issue, kindly add following tag as appropriate
> >>>>> Reported-by: kernel test robot <lkp@intel.com>
> >>>>>
> >>>>> All errors (new ones prefixed by >>, old ones prefixed by <<):
> >>>>>
> >>>>>>> gcc-5: error: -gz is not supported in this configuration
> >>>>
> >>>> Hmm...I wonder if the feature detection is incomplete?  I suspect it's
> >>>> possible to not depend on zlib.
> >>>>
> >>>>> make[2]: *** [scripts/Makefile.build:277: scripts/mod/empty.o] 
> >>>>> Error 1
> >>>>> make[2]: Target '__build' not remade because of errors.
> >>>>> make[1]: *** [Makefile:1169: prepare0] Error 2
> >>>>> make[1]: Target 'prepare' not remade because of errors.
> >>>>> make: *** [Makefile:185: __sub-make] Error 2
> >>>
> >>> The output of gcc-5 -v --version on that machine may help. The
> >>> convoluted gcc_cv_ld_compress_de logic in gcc/configure.ac may be
> >>> related, but I can't find any mistake that our
> >>> CONFIG_DEBUG_INFO_COMPRESSED conditions may make.
> >>

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?