Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site lsuc.UUCP
Path: utzoo!utcs!mnetor!lsuc!msb
From: msb@lsuc.UUCP (Mark Brader)
Newsgroups: net.lang.c
Subject: Re: "handy.h"
Message-ID: <782@lsuc.UUCP>
Date: Thu, 5-Sep-85 12:55:20 EDT
Article-I.D.: lsuc.782
Posted: Thu Sep  5 12:55:20 1985
Date-Received: Thu, 5-Sep-85 14:19:21 EDT
References: <10200006@ada-uts.UUCP> <532@linus.UUCP> <699@whuxl.UUCP>
Reply-To: msb@lsuc.UUCP (Mark Brader)
Organization: Law Society of Upper Canada, Toronto
Lines: 29
Summary: Some of those suggestions are dangerous


Michael Baldwin (whuxl!mike) suggests, among others:

> #define	NELEM(arr)	(sizeof (arr) / sizeof *(arr))
> #define	LAST(arr)	((arr) + NELEM(arr))
> 	for (pp = potato; pp < LAST(potato); pp++)

and

> #define	COPY(a,b)	strncpy(a,b,sizeof a)

These are dangerous.  LAST is misnamed, because it points to the
space after the last element.  If used, it should be called
something like AFTERLAST.

And with COPY, there is a temptation to call it with arguments of the
wrong type.  Can't you just see somebody writing

	fun(s)
	char s[];
	{
		char temp[PLENTY_BIG];
		...
		COPY (s, temp);	/* WRONG */
	}

and wondering why only the first few bytes were copied?

Mark Brader