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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Fri, 29 Jan 2021 14:27:09 -0800
Message-ID: <CAKwvOdmrSNNkfFc7U3h2qWnNc+okxeBravE4Huun_LOv75_Bvw@mail.gmail.com>
Subject: Re: [PATCH v6 2/2] Kbuild: implement support for DWARF v5
To:     Jakub Jelinek <jakub@redhat.com>
Cc:     Nick Clifton <nickc@redhat.com>,
        Sedat Dilek <sedat.dilek@gmail.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Nathan Chancellor <natechancellor@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Clang-Built-Linux ML <clang-built-linux@googlegroups.com>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        Fangrui Song <maskray@google.com>,
        Caroline Tice <cmtice@google.com>, Yonghong Song <yhs@fb.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Andrii Nakryiko <andrii@kernel.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Arvind Sankar <nivedita@alum.mit.edu>
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On Fri, Jan 29, 2021 at 1:11 PM Jakub Jelinek <jakub@redhat.com> wrote:
>
> On Fri, Jan 29, 2021 at 01:05:56PM -0800, Nick Desaulniers wrote:
> > > Wasn't that fixed in GAS?
> > > https://sourceware.org/bugzilla/show_bug.cgi?id=27195
> >
> > $ make LLVM=1 -j72 defconfig
> > $ ./scripts/config -e DEBUG_INFO -e DEBUG_INFO_DWARF5
> > $ make LLVM=1 -j72
> > ...
> > /tmp/init-d50d89.s: Assembler messages:
> > /tmp/init-d50d89.s:10: Error: file number less than one
> > /tmp/init-d50d89.s:11: Error: junk at end of line, first unrecognized
> > character is `m'
> >
> > which is https://sourceware.org/bugzilla/show_bug.cgi?id=25611.
> >
> > $ as --version | head -n1
> > GNU assembler (GNU Binutils for Debian) 2.35.1
> >
> > Maybe GAS should not need to be told -gdwarf-5 to parse these?  Then
> > we would not need to pass -Wa,-gdwarf-5 via clang with
> > -no-integrated-as.
>
> That is what sw#27195 is about, just try current binutils 2.35, 2.36 or
> trunk branches.

Ok, yep, I can confirm.  I just built ToT binutils and I no longer
need to specify -Wa,-gdwarf-5 when building with clang with
-no-integrated-as.

I will update scripts/test_dwarf5_support.sh to check for that and
update the comments/documentation/commit messages to say binutils
2.35.2+, link to https://sourceware.org/bugzilla/show_bug.cgi?id=27195
instead, then drop hunk that was passing -Wa,-gdwarf-5.
-- 
Thanks,
~Nick Desaulniers