From owner-freebsd-hackers@FreeBSD.ORG  Mon Aug 13 08:24:51 2012
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Date: Mon, 13 Aug 2012 12:54:36 +0430
From: Hooman Fazaeli <hoomanfazaeli@gmail.com>
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Subject: How to know __FreeBSD_version for a symbol
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Hi hackers

In the process of back porting drivers to older freebsd versions,
We sometimes need to add suitable '#if __FreeBSD_version >= xxxxx ... else ... '
directives to the source to use an alternate function or exclude certain
statements, defines, etc.

What is the best (quick/reliable) way to know in which __FreeBSD_version
a symbol (function, struct member, macro, ...) has been first introduced?