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

[David Holland <dholland-bugs%netbsd.org@localhost>]

The following reply was made to PR kern/43063; it has been noted by GNATS.

From: David Holland <dholland-bugs%netbsd.org@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: kern/43063: Please delete __NetBSD_Prereq__() from <sys/param.h>
Date: Sun, 13 Jul 2014 16:55:00 +0000

 On Sun, Jul 13, 2014 at 02:20:01PM +0000, Joerg Sonnenberger wrote:
  >  >  /* This was fixed in NetBSD */
  >  >  #ifdef __NetBSD_Prereq__
  >  >  #  if __NetBSD_Prereq__(6, 99, 20)
  >  >  #    undef IPV6_POLLADDRFLAG
  >  >  #  endif
  >  >  #endif
  >  >  
  >  >  Should this be now be moved to a ./configure test based on uname -m?
  >  >  ./configure is NOT run when dhcpcd is imported into external so that may
  >  >  complicate future pullups if changed.
  >  
  >  Just use __NetBSD_Version directly?
 
 Anyway, yeah, the problem with __NetBSD_Prereq__ is that you can't
 tell by looking at the name of it whether it means "before 6.99.20" or
 "after 6.99.20", and NetBSD versions (including releases) have been
 shipped both ways.
 
 So it's much better to write
 
    #if __NetBSD_Version__ >= 699002000
 
 although as I noted some years ago, it might be better to avoid
 exposing the bit encoding of the number, something like
 
    #if __NetBSD_Version__ >= __NetBSD_mkversion__(6, 99, 20)
 
 The problem with that is that writing a macro that handles all the
 variants (including post-release stable branches and so on) isn't
 entirely trivial.
 
 The last time I made an attempt to get this settled there wasn't a
 whole lot of opposition to fixing it, but there wasn't a clear
 consensus on how either and so it didn't get done.
 
 -- 
 David A. Holland
 dholland%netbsd.org@localhost