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From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: comp.lang.c
Subject: Re: Problem with either ANSI 'C' or Dr Dobbs Journal.
Message-ID: <8415@utzoo.UUCP>
Date: Sat, 15-Aug-87 18:17:12 EDT
Article-I.D.: utzoo.8415
Posted: Sat Aug 15 18:17:12 1987
Date-Received: Sat, 15-Aug-87 18:17:12 EDT
References: <449@sugar.UUCP> <8383@utzoo.UUCP>, <894@haddock.ISC.COM>
Organization: U of Toronto Zoology
Lines: 24

> "A.6.2 Undefined behavior: ... A function that accepts a variable number of
> arguments is called, but no prototype declarator with the ellipsis notation
> is in scope."  [Oct86 dpANS]
> 
> In other words, a variadic function must have a prototype.  This implies that
> a function called without a prototype in scope may be assumed to have a fixed
> number of arguments.

Correct -- I think -- but only after considerable study.  A.6.2 is in the
appendix, thus is *not* part of the standard.  Careful study of 3.3.2.2
*suggests* the truth of the A.6.2 note, but I wouldn't want to have to try
to prove it rigorously from the current wording.  3.3.2.2 observes:  "If
no function prototype declarator is in scope... [and] the number of arguments
does not agree with the number of formal parameters, the behavior is
undefined."  So far so good... but what *is* the "number of formal parameters"
for a variadic function??  3.5.3.3, Function Declarators, gives vague and
inconsistent hints but no definitive guidance.  Unless I have missed some
clear statement somewhere else, I think wording changes are in order -- the
A.6.2 statement is not unambiguously supported by the standard proper.  The
simplest fix would be to add the A.6.2 statement quoted above somewhere
around line 8 of 3.3.2.2 (draft of 1 Oct 1986).  [Doug, you listening?]
-- 
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