Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!nic.MR.NET!srcsip!sip7!colburn
From: colburn@sip7.SRC.Honeywell.COM (Mark H. Colburn)
Newsgroups: comp.sys.ibm.pc
Subject: Re: TC2.0 bugfree ?
Message-ID: <16344@srcsip.UUCP>
Date: 7 Feb 89 17:23:34 GMT
References: <3785@druwy.ATT.COM>
Sender: news@src.honeywell.COM
Reply-To: colburn@sip7.UUCP (Mark H. Colburn)
Organization: Honeywell Systems & Research Center, Camden, MN
Lines: 30

In article <3785@druwy.ATT.COM> rhm@druwy.UUCP (MasseyR) writes:
>	i = (*cp++ << 8) + *cp++;

>note that si (i.e. cp) is not incremented between references
>but instead after both references.

Note, that this is not necesarily incorrect.  It is undefined to
include two operations with side effects which reference the same
variable.  Among other things it is bad coding style.  Worse, it
provides unexpected results on a number of compilers.

The code would be better written:

	i = (*cp << 8) + *(cp + 1);
	cp += 2;

One of the classic examples of side effects is given below:

	i = 10;
	i++ = 10 * i++;

what is the value of I going to be?  111? 120?  Remember
that C may entirely reorder your expression before evaluating it.

You shouldn't write code like that.


Mark H. Colburn           MN65-2300		colburn@SRC.Honeywell.COM
Systems Administration and Support
Honeywell Systems & Research Center