Subject: Re: ancillary data alignment and binary backward compatibility: please pick one
To: None <>
From: Jason Thorpe <>
List: tech-net
Date: 02/28/2000 10:02:41
On Mon, 28 Feb 2000 21:32:23 +0900 wrote:

 > second multipart attachment:
 > 	- use sysctl to get alignment constraint for CMSG_ALIGN().
 > 	- no dependency from sys/socket.h to machine/param.h.
 > 	- CMSG_xx are non-constant.  you can't do the following:
 > 		char foo[CMSG_SPACE(int)];
 > 	- old compiled binary is okay on new kernel, even if they sees
 > 	  different defined in machine/param.h.
 > 	- extra function calls on CMSG_ALIGN().  (we can decrease them by
 > 	  making static variable visible, I thought it would be safer to
 > 	  keep it inside function)

I think I vote for this one, too.

Note that in the case of an automatic variable, CMSG_SPACE(...) will
still work because of a GCC extension.

BTW, make sure to make the copyright date correct :-), and bump the libc

        -- Jason R. Thorpe <>