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From: guy%gorodish@Sun.COM (Guy Harris)
Newsgroups: comp.lang.c
Subject: Re: Function prototypes versus open()
Message-ID: <22194@sun.uucp>
Date: Fri, 26-Jun-87 15:22:23 EDT
Article-I.D.: sun.22194
Posted: Fri Jun 26 15:22:23 1987
Date-Received: Sat, 27-Jun-87 10:48:36 EDT
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> Well, I don't know about the AT&T implementation, but the BSD open()
> most emphatically does not have an optional third argument!  It has
> three, exactly three, arguments.  It just happens that on most BSD
> machines, you can get away with passing fewer arguments that the
> routine wants provided it ignores the extra ones.

The BSD implementation very closely resembles the System III/System V
implementation, so the argument is as optional in one as it is in the
other.

> This means that you can get away with pretending it's optional, but that
> doesn't make it optional at all.  Wait for the day you have to port to a
> machine whose compiler treats optional arguments differently - it'll be
> the day this burns you.

Actually, it'll be the day it burns the person who ports UNIX to that
machine; "open()" used to take two arguments, and there are plenty of
programs left around that weren't changed when "open" was changed.
This is, I presume, why Karl Heuer complained about the 3-argument
"open"; introducing it technically rendered *all* programs that used
a two-argument "open" invalid!
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy@sun.com