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Date: Fri, 23 Oct 2015 14:21:37 -0700
Message-ID: <CAGHfRMChOVVEZi+KWqNmTdXSr6HWg24uiKaNrqpg_LwD=sSi4Q@mail.gmail.com>
Subject: Re: svn commit: r289773 - in head: sbin/sysctl sys/kern sys/sys
From: NGie Cooper <yaneurabeya@gmail.com>
To: Mark Linimon <linimon@lonesome.com>
Cc: Conrad Meyer <cem@freebsd.org>,
 "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, 
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On Fri, Oct 23, 2015 at 2:06 PM, Mark Linimon <linimon@lonesome.com> wrote:
> On Fri, Oct 23, 2015 at 08:09:35AM -0700, Conrad Meyer wrote:
>> What is __FreeBSD_version and why would it be bumped?
>
> __FreeBSD_version was introduced in the following commit:
>
>   https://svnweb.freebsd.org/base/head/sys/sys/param.h?r1=34924&r2=36260
>
> where it has been ever since:
>
>   https://svnweb.freebsd.org/base/head/sys/sys/param.h?view=log
>
> This variable exists to tell the Ports Collection, among others,
> that "something has changed that may require you to patch and/or
> recompile."
>
> The historical values are documented in
>
>   https://www.freebsd.org/doc/en/books/porters-handbook/versions.html#freebsd-versions-table
>
> Your mentor should have shown you this information.

It's also really handy if you know that a KPI exists after `#if
__FreeBSD_version > XYZ`. It doesn't work for folks who cherry-pick
(like we do at $work, iXsystems with "NextBSD"/"TrueOS", etc), but it
works for some upstream folks -- especially when you have something
that uses a KPI in flux on a CURRENT branch for instance... *cough*
see open-vm-tools and breakage due to vm(4) APIs being in flux (
:/..).