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From: daifuku@yumyum.esd.sgi.com (Peter Daifuku)
Newsgroups: comp.sys.apollo
Subject: Re: function prototype mystery?
Message-ID: <1991Apr12.013850.2047@odin.corp.sgi.com>
Date: 12 Apr 91 01:38:50 GMT
References: <1991Apr11.164655.17092@milton.u.washington.edu>
Sender: news@odin.corp.sgi.com (Net News)
Reply-To: daifuku@yumyum.esd.sgi.com (Peter Daifuku)
Organization: Silicon Graphics Inc.
Lines: 30

> void proc2_$get_info(
>         uid_$t          &p2_uid,
>         proc2_$info_t   *info,
>         pinteger        &info_buf_len,  /* size of info buffer (bytes) */
>         status_$t       *sts
> );
> 
> What do the &'s do to the first and third arguments?
> It looks to me like the function expects addresses, but if
> I pass addresses to it, the compiler (cc 6.7.m, OS10.3) complains
> that the argument type conflicts with the declaration.
> 
> What works is something like
proc2_$get_info(p2_uid,&info,bufferlength,&status).Why? Is this some
kind of > > apollo-ism, or something ANSI-like?

This one threw me for a loop too, when I first encoutered it.
It's actually a C++-ism, and thus an APOLLO enhancement to C. It allows you to
pass arguments by reference, without specifically passing the address.
Hence, the
caller sends p2_uid, as opposed to &p2_uid, and the callee can reference p2_uid
directly, instead of *p2_uid. Since the argument is being passed by reference,
any modifications by the callee are seen by the caller.


Peter Daifuku               Silicon Graphics
daifuku@sgi.com             Mountain View, CA 94039

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