Func Protos with K&R Func Defs

[Chris Torek]

In article <BPX9AT9 at xds13.ferranti.com> peter at ficc.ferranti.com
(Peter da Silva) writes:
>So you're saying that the compiler is not allowed to take advantage of the
>prototype information and use (for example) callee saves or special LINK
>instructions when calling prototyped functions?

This statement is correct (in a strict logical sense), but all the
implications it makes are wrong.  That is, the statement

	[compiler treats prototyped functions specially] implies
		[compiler may not take advantage of...]

is true but only because the clause [compiler treats prototyped
functions specially] is false.  Aside from default promotions,
prototyped functions and non-prototyped functions are treated
identically.  In particular, the compiler make take advantage of
special LINK or RET instructions for non-prototyped functions as
well as for the prototyped versions.

The only special case is varargs functions, which *must* be declared
using the new prototype varargs syntax.  All other functions may be
assumed to take fixed argument lists.  In other words,

	f(fmt, a1, a2, a3, a4, a5) char *fmt; {
		printf(fmt, a1, a2, a3, a4, a5);
	}
	...
		f("%d\n", 3);

is illegal, because the caller did not supply the proper number and
type of arguments.
-- 
In-Real-Life: Chris Torek, Lawrence Berkeley Lab EE div (+1 415 486 5427)
Berkeley, CA		Domain:	torek at ee.lbl.gov