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From: gwyn@smoke.BRL.MIL (Doug Gwyn)
Newsgroups: comp.std.c
Subject: Re: Parameter Types in Old-Style Function Definitions
Keywords: parameter, function
Message-ID: <13779@smoke.BRL.MIL>
Date: 9 Sep 90 21:15:10 GMT
References: <10391@pt.cs.cmu.edu> <2689@dataio.Data-IO.COM> <1990Sep8.053408.2005@alphalpha.com>
Organization: U.S. Army Ballistic Research Laboratory, APG, MD.
Lines: 21

In article <1990Sep8.053408.2005@alphalpha.com> nazgul@alphalpha.com (Kee Hinckley) writes:
>foo(c, i)
>char	c;
>int	i;
>{}
>extern foo(char c, int i);

These are not guaranteed to be compatible, since the definition uses
default-widened parameter types but the prototype declaration uses
unwidened (in general) types.  Implementations that always default
widen arguments even for new-style functions linkage will probably
support this mixture, but other implementations will not.

The general coding rule for fixed-argument functions is:
	EITHER  always use already-default-widened parameter types
	OR ELSE always use prototypes, never old-style declarations
		or definitions
(For variable-argument functions, always use prototypes including ",..."
and use appropriate <stdarg.h> macros in the function definitions.)
If you try to mix old- and new-style syntax, you risk running afoul
of the genuine differences in linkage for the two styles.