Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!killer!vector!rpp386!jfh
From: jfh@rpp386.Dallas.TX.US (The Beach Bum)
Newsgroups: comp.lang.c
Subject: Re: Undeclared function arguments
Summary: Me first ;-)
Message-ID: <8058@rpp386.Dallas.TX.US>
Date: 18 Oct 88 23:19:52 GMT
References: <13168@dhw68k.cts.com> <2686@hound.UUCP>
Reply-To: jfh@rpp386.Dallas.TX.US (The Beach Bum)
Distribution: na
Organization: River Parishes Programming, Dallas TX
Lines: 45

In article <2686@hound.UUCP> rkl1@hound.UUCP (K.LAUX) writes:
>	The reason that 'm' was not declared was that the body of the
>function did not reference the variable at all *AND* it was the last
>parameter in the formal argument list.  Since arguments are pushed on
>the stack from *right* to *left*, there was no need to know its size.

This is not portable, relevant, or correct.

The formal argument `m' has a default type of `m', hence the type and
size are known, as a matter of fact.  Regardless of `m' being referenced,
the type will always default to `int'.

The order of arguments on the stack, or even the existance of a stack,
is not an issue which is addressed by the language specification.  There
exists hardware in which a function with two arguments will pass the
actual parameters are passed in registers or pre-allocated regions of
memory.

>	It would be a different case if:
>
>	YYBACK (i, m, n)
>	
>	and only i and n were referenced because now the compiler would
>*have* to know the size of m in order to correctly reference n on the stack.

This would be correct if the size of `m' were not set by default to be
sizeof (int).  If the call were

YYBACK (i, m, n)
int	i;
struct	foo	m;
int	n;

and the size of `m' weren't known, THEN it MIGHT be an issue.  However,
only structure pointers do not require the size of the underlying structure
to be known.  Since `m' in this case is not a pointer, this exception does
not apply and the above example is illegal.

C provides that undeclared formal parameters default to type `int'.  This
may not be a wonderful idea, but it does cover this situation.
-- 
John F. Haugh II                        +----Make believe quote of the week----
VoiceNet: (214) 250-3311   Data: -6272  | Nancy Reagan on Richard Stallman:
InterNet: jfh@rpp386.Dallas.TX.US       |          "Just say `Gno'"
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