kern/43063: Please delete __NetBSD_Prereq__() from <sys/param.h>

[kre%munnari.OZ.AU@localhost]

>Number:         43063
>Category:       kern
>Synopsis:       Please delete __NetBSD_Prereq__() from <sys/param.h>
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Fri Mar 26 12:30:00 +0000 2010
>Originator:     Robert Elz
>Release:        current (or anything recent)
>Organization:
        Prince of Songkla University
>Environment:
System: NetBSD jade.coe.psu.ac.th 4.0_STABLE NetBSD 4.0_STABLE 
(JADE-1.696-20080517) #9: Fri May 23 18:55:13 ICT 2008 
kre%jade.coe.psu.ac.th@localhost:/usr/obj/4/kernels/JADE i386
Architecture: i386
Machine: i386
>Description:
        The __NetBSD_Prereq__() in <sys/param.h> was changed from
        testing __NetBSD_Version__ >= m.n to testing
        __NetBSD_Version <= m.n in version 1.242 of <sys/param.h>

        That is, its sense was entirely reversed.   Which is the
        correct version is irrelevant now (I kind of believe the
        former, but I might be rationalising its intended use based
        upon the definition I first saw).

        The effect is that it is impossible (in sources outside of
        NetBSD's control) for anyone to sanely use this macro, as
        they'd have no way of telling which version they were going
        to get (or at least, not without doing the test that
        the macro is designed to do in another way first...)

        It could still be used inside NetBSD, where its usage could be
        synchronised with the system, but it isn't - that is, I did a
        complete search of all the NetBSD current, and the only reference
        to the macro was the one in sys/param.h

        That is, it is not used the only place it could safely be used.
        If something similar is ever needed, it can be recreated
        with a new name, and a safe to use definition.   For now,
        please delete it, so any external code that might happen to
        use the thing (obviously I can't search all the world's code
        to check) will fail with a compile error (trivially fixed)
        rather than generating an unknowable test, and on some systems
        (the ones where the test is the "wrong" way for the application)
        bizarre results.

>How-To-Repeat:
        By inspection.
>Fix:

ed src/sys/sys/param.h <<!
/__NetBSD_Prereq__/;+2d
w
q
!