linux-kernel - Re: Linux 4.19 and GCC 9

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Date:   Mon, 10 Jun 2019 10:32:25 +0100
From:   Ignat Korchagin <ignat@...udflare.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Ivan Babrou <ivan@...udflare.com>,
        Arnaldo Carvalho de Melo <arnaldo.melo@...il.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

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?

Regards,
Ignat


On Mon, Jun 10, 2019 at 8:45 AM Greg KH <gregkh@...uxfoundation.org> wrote:
>
> On Mon, Jun 10, 2019 at 12:21:51AM -0700, Ivan Babrou wrote:
> > Looks like 4.19.49 received some patches for GCC 9+, but unfortunately
> > perf still doesn't want to compile:
> >
> > [07:15:32]In file included from /usr/include/string.h:635,
> > [07:15:32] from util/debug.h:7,
> > [07:15:32] from builtin-help.c:15:
> > [07:15:32]In function 'strncpy',
> > [07:15:32] inlined from 'add_man_viewer' at builtin-help.c:192:2,
> > [07:15:32] inlined from 'perf_help_config' at builtin-help.c:284:3:
> > [07:15:32]/usr/include/x86_64-linux-gnu/bits/string3.h:126:10: error:
> > '__builtin_strncpy' output truncated before terminating nul copying as
> > many bytes from a string as its length [-Werror=stringop-truncation]
> > [07:15:32] 126 | return __builtin___strncpy_chk (__dest, __src, __len,
> > __bos (__dest));
> > [07:15:32] | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > [07:15:32]builtin-help.c: In function 'perf_help_config':
> > [07:15:32]builtin-help.c:187:15: note: length computed here
> > [07:15:32] 187 | size_t len = strlen(name);
> > [07:15:32] | ^~~~~~~~~~~~
> > [07:15:32]cc1: all warnings being treated as errors
>
>
> Any chance in finding a patch in Linus's tree that resolves this?  I
> don't have gcc9 on my systems here yet to test this.
>
> thanks,
>
> greg k-h
>
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