linux-kernel - Re: Linux 4.19 and GCC 9

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Date:   Tue, 25 Jun 2019 15:50:29 +0800
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Ignat Korchagin <ignat@...udflare.com>
Cc:     Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>,
        Ivan Babrou <ivan@...udflare.com>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        kernel-team <kernel-team@...udflare.com>
Subject: Re: Linux 4.19 and GCC 9

On Mon, Jun 24, 2019 at 11:42:34AM +0100, Ignat Korchagin wrote:
> 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)

I am on the road and getting to backports for this stuff is on the
bottom of my list until next week at the earliest, sorry.

> > 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/

Yes, my laptop just updated, so I'm building here.  Some gcc9 patches
did just get backported, but not for perf.

thanks,

greg k-h