RE: ds alignment (was Prototyping printf())

["David Morris" <dmorris@xxxxxxxxxxxxx>]

Barbara,

Last October, Midrange Computing ran an article titled "Put it in Storage".   
The code 
in that article describes using user spaces and user indexes to store data.  
One feature 
is an align procedure that ensures a pointer type variable is on a 16 byte 
boundary.   
Subprocedure AlnOff in the file fig6_stgtkt.txt adjusts an offset to a 
boundary. I rely on 
this code extensively and have not had any problems.  The only assumption is 
that a 
User Space is aligned.  If this assumption is incorrect, at least everything is 
going 
through a single interface.  You can get the source at:

http://www.midrangecomputing.com/ftp/prog/99/991004.zip 

David Morris

>>> bmorris@ca.ibm.com 10/10/00 07:27AM >>>

>Date: Fri, 6 Oct 2000 14:42:24 -0400
>From: Jon.Paris@hal.it 
>
>I believe that a DS is always 16 byte aligned, and even if not the use of
>the ALIGN keyword would do the job for you.

John, the ALIGN keyword doesn't force 16-byte alignment.  It just forces
integer and float types to be correctly aligned.  A 4F would cause the
DS to be at least 4-byte aligned; a 20i would cause the DS to be at least
8-byte aligned.

Only the presence of a pointer forces a 16-byte alignment (whether or
not you have ALIGN coded).

Even if a DS is always currently 16-byte aligned (is it?), it's not a
documented feature, and shouldn't be counted on.

Barbara Morris

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