Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site callan.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxn!ihnp4!qantel!hplabs!sdcrdcf!trwrb!scgvaxd!wlbr!callan!tim
From: tim@callan.UUCP (Tim Smith)
Newsgroups: net.lang.c
Subject: Re: C programming hint
Message-ID: <1057@callan.UUCP>
Date: Mon, 29-Jul-85 21:11:27 EDT
Article-I.D.: callan.1057
Posted: Mon Jul 29 21:11:27 1985
Date-Received: Sat, 3-Aug-85 05:32:10 EDT
References: <899@teddy.UUCP>
Organization: Callan Data Systems, Westlake Village, CA
Lines: 17

> 	char blanks[SIZE];	/* declare array of SIZE elements */
> 	
> 	blanks[0] = ' ';	/* initialize 1st element */
> 
> 	strncpy(blanks + 1, blanks, SIZE - 1);	/* initialize entire array */

Danger Will Robinson! Danger Will Robinson!  Non-portable contruct.  Unsafe
assumptions about implementation of strncpy.  Danger Will Robinson!

If strncpy is done in assembly for efficiency, and the machine has a block
tranfer instruction, and the author of strncpy used it, and the machine is
smart about copying strings, then the above will fail, because the machine
will recognize that the source and destinations overlap, with the destination
above the source, so it will copy the string from the back.
-- 
					Tim Smith
				ihnp4!{cithep,wlbr!callan}!tim