Variable arguments to & from functions.

[der Mouse]

In article <1991Jun17.205314.25401 at cbnewsm.att.com>, akshay at cbnewsm.att.com (akshay.kumar.deshpande) writes:

> I am trying to write a variable argument function which in turn calls
> another variable argument function.  Can anybody tell me how to pass
> the unknown arguments I receive to the next function.
(Questions generally end with `?' instead of `.'.)

> Here is a psuedo example:

[compressed -dM]
> A(int arg1, ...) {
> 	va_start(ap, fmt);  /* from K&R 2nd edition - p 156 */
> 	B(arg1, arg2, arg3, <...>);
> }

> B(int arg1, int arg2, int arg3, ...); { ... }

> I would like to have the "..." of A match that for the function call
> of B.

Sorry, can't be done.  You have to provide a v- form of B that takes a
va_list parameter and then call that from A.  (You should probably do
this anyway; in fact, a normal thing to do would be to have B just call
its varargs version.)

Note also that va_start takes the name of the last fixed argument,
which is arg1, not fmt.  (You can't just blindly copy code from K&R;
you have to understand it first, if only minimally.)

Something like (declarations omitted; also don't forget the va_end()
calls)

A(int arg1, ...) {
	va_start(ap, arg1);
	vB(arg1, arg2, arg3, ap);
}

B(int arg1, int arg2, int arg3, ...); {
	va_start(ap,arg3);
	vB(arg1,arg2,arg3,ap);
}

vB(int arg1, int arg2, int arg3, va_list ap) {
	...do the real B here...
}

					der Mouse

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