Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!gorodish!guy
From: guy%gorodish@Sun.COM (Guy Harris)
Newsgroups: comp.arch
Subject: Re: register windows
Message-ID: <29935@sun.uucp>
Date: Sun, 4-Oct-87 00:06:01 EDT
Article-I.D.: sun.29935
Posted: Sun Oct  4 00:06:01 1987
Date-Received: Wed, 7-Oct-87 04:05:42 EDT
References: <1242@k.gp.cs.cmu.edu>
Sender: news@sun.uucp
Distribution: na
Lines: 23

> Lose#4: Some programs (particularly Unix's "printf" ) want their parameter
> 	list to be at an address.
> 
> What ways have been used around lose#4 ?

Our "printf" uses the "varargs" package, our "varargs.h" include file maps
"va_alist" into "__builtin_va_alist" on SPARC machines, and our SPARC compiler
recognizes the "__builtin_va_alist" construct and moves arguments from
registers to memory as needed.  Basically, if you want code using
"varargs"-like techniques to work on machines built around the SPARC chip,
you'd better not just use any "varargs"-like technique, you'd better use
"varargs".  (ANSI C contains a similar facility, and mandates its use in this
case.)

Note that this is a lose of any implementation where arguments are passed in
registers; it can either be supported by requiring this sort of code to be
written using higher-level primitives such as "varargs" rather than low-level
fiddling, or by having the compiler somehow detect that the low-level tricks
are being used (as I believe MIPSco's compiler for their non-register-window
machine does).
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy@sun.com