Parameter Types in Old-Style Function Definitions

[Doug Gwyn]

In article <1990Sep8.053408.2005 at alphalpha.com> nazgul at 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.