Path: utzoo!attcan!uunet!lll-winken!lll-lcc!lll-tis!helios.ee.lbl.gov!pasteur!ucbvax!VENUS.YCC.YALE.EDU!LEICHTER
From: LEICHTER@VENUS.YCC.YALE.EDU ("Jerry Leichter ", LEICHTER-JERRY@CS.YALE.EDU)
Newsgroups: comp.os.vms
Subject: re: LIB$INIT_TIMER
Message-ID: <8805260828.AA19768@ucbvax.Berkeley.EDU>
Date: 24 May 88 16:25:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 24


	The documentation for LIB$INIT_TIMER states that it takes different
	actions base on whether the argument handle-adr is absent, zero, or
	non-zero.

	How do you get the "absent" effect when calling from C?  I have
	invariably found that I have to specify a 0 explicitly as a parameter
	when calling system routines where if I were using FORTRAN I would
	leave the argument blank.

LIB$INIT_TIMER takes one argument, handle-adr; it is passed by reference.

An optional argument may be omitted by passing 0 by value; or, if it is a
trailing argument, by omitting it entirely.  (The latter method won't work
for system services, but will work for RTL calls.)

So:

	char *cb = 0;		/* Control block address		*/
	LIB$INIT_TIMER(&cb);	/* Allocate control block, set cb	*/
	LIB$INIT_TIMER(&cb);	/* Re-use allocated control block	*/
	LIB$INIT_TIMER(0);	/* Use static control block		*/
	LIB$INIT_TIMER();	/* The same thing			*/

							-- Jerry