Subject: Re: ancillary data alignment and binary backward compatibility
To: None <>
From: Chris G. Demetriou <>
List: tech-net
Date: 03/11/2000 22:15:30 writes:
> 	I'm very convinced that ALIGNBYTES is correct here.  We can't foresee
> 	what kind of structs are put into ancillary message.  If we use
> 	something smaller than ALIGNBYTES, every time we pass new struct via
> 	ancillary message (which exceeds the alignment defined) we need to
> 	change CMSG_ALIGN and we'll have binary compatibility issue.

yeah, i think i believe this, however...

> 	So, at least need to bump from 3 to ALIGNBYTES.
> 	- How to bump
> 	- how to determine ALIGNBYTES (statically by header of hw.alignbytes
> 	  sysctl MIB)
> 		current tree uses hw.alignbytes
> 	is still not 100% decided...

ALIGNBYTES is something that can't change for a given MACHINE_ARCH (or
shouldn't, unless there's a big flag day for that port).

There's no reason to do this using a sysctl.  it just adds overhead.

Chris Demetriou - -
Disclaimer: Not speaking for NetBSD, just expressing my own opinion.