linux-kernel - Re: [RFC PATCH 0/3] kbuild: generate intermediate C files instead of copying

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Date:   Fri, 8 Sep 2017 11:39:32 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Sam Ravnborg <sam@...nborg.org>, Michal Marek <mmarek@...e.com>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Rob Herring <robh@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Richard Purdie <richard.purdie@...uxfoundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Nicholas Piggin <npiggin@...il.com>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Markus Heiser <markus.heiser@...marit.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        SeongJae Park <sj38.park@...il.com>,
        "Yann E. MORIN" <yann.morin.1998@...e.fr>
Subject: Re: [RFC PATCH 0/3] kbuild: generate intermediate C files instead of
 copying _shipped files

On Fri, Sep 8, 2017 at 11:01 AM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> It doesn't seem to happen for every exported symbol, though. Odd.

Fascinating.

Picking one file at random that shows this, I did net/ceph/mon_client.c.

The version file that gets generated for that looks like this:

__crc_ceph_monc_want_map = 0x3389a57e;
__crc_ceph_monc_got_map = 0x707f45a2;
__crc_ceph_monc_renew_subs = 0x9842030a;
__crc_ceph_monc_wait_osdmap = 0xfe38746d;
__crc_ceph_monc_open_session = 0xc9ba8a19;
__crc_ceph_monc_do_statfs = 0xe878801b;
__crc_ceph_monc_get_version = 0xfaac6ce0;
__crc_ceph_monc_get_version_async = 0x3adefe28;
__crc_ceph_monc_blacklist_add = 0xee71d0ef;
__crc_ceph_monc_init = 0xfce99654;
__crc_ceph_monc_stop = 0xb0d197d0;
__crc_ceph_monc_validate_auth = 0xce1c6d69;

and with the gperf-removal patch, it is 100% identical _except_ that
the "__crc_ceph_monc_do_statfs" line is missing.

Same hashes for everything else. But one missing line. WTF?

What is special about that one particular function vs the other ones
in that file? I have absolutely no idea.

So the really odd thing here is how things clearly still _work_. The
parser works fine for everything else. And looking at the
gprof-removal patch it's not at all obvious how everything could work
fine except for some random thing.

Strange. Does anybody see what the pattern to the failure is?

                Linus