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From:   Ignat Korchagin <ignat@cloudflare.com>
Date:   Mon, 24 Jun 2019 11:42:34 +0100
Message-ID: <CALrw=nFcp-+C7ceTFj=R=aG0Z5OpRRVXFoUxUoh=CjcfW79-+g@mail.gmail.com>
Subject: Re: Linux 4.19 and GCC 9
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>,
        Ivan Babrou <ivan@cloudflare.com>,
        Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Ingo Molnar <mingo@redhat.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        kernel-team <kernel-team@cloudflare.com>
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Sender: linux-kernel-owner@vger.kernel.org
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Hi Greg,

> > For us it seems applying the following 4 mainline patches makes 4.19.x
> > branch perf compile with GCC-9:
> >
> > 4d0f16d059ddb91424480d88473f7392f24aebdc: perf ui helpline: Use
> > strlcpy() as a shorter form of strncpy() + explicit set nul
> > b6313899f4ed2e76b8375cf8069556f5b94fbff0: perf help: Remove needless
> > use of strncpy()
> > 5192bde7d98c99f2cd80225649e3c2e7493722f7: perf header: Fix unchecked
> > usage of strncpy()
> > 97acec7df172cd1e450f81f5e293c0aa145a2797: perf data: Fix 'strncat may
> > truncate' build failure with recent gcc
> >
> > I also checked that 4.19.49 compiles fine with GCC 9, although with a
> > lot of warnings, mostly from objtool, like "warning: objtool:
> > sock_register()+0xd: sibling call from callable instruction with
> > modified stack frame". But it's a start.
> >
> > Can we apply the above-mentioned patches, please?

> I'll look into these after the next round of kernels are released.  I

Did you by any chance forget to queue these patches? :) (the build is
still broken for GCC 9.1)

> guess I'll go find a distro that has gcc9 on it to actually test
> things...

BTW, Arch already has GCC 9.1 package, so no need to compile your own
anymore for testing:
https://www.archlinux.org/packages/core/x86_64/gcc/

Regards,
Ignat