Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!unmvax!aplcen!haven!adm!smoke!gwyn
From: gwyn@smoke.BRL.MIL (Doug Gwyn)
Newsgroups: comp.lang.c
Subject: Re: evaluation order
Message-ID: <11060@smoke.BRL.MIL>
Date: 14 Sep 89 11:52:24 GMT
References: <9361@attctc.Dallas.TX.US>
Reply-To: gwyn@brl.arpa (Doug Gwyn)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 9

In article <9361@attctc.Dallas.TX.US> bobc@attctc.Dallas.TX.US (Bob Calbridge) writes:
>if (write(handle, buf, len=strlen(buf)) != len) do_something();
>can I be assured that 'len' will be assigned the length of 'buf' before it
>is used on the right side of the comparison operator.

No.
Either side of != may be evaluated first, depending on the implementation.
It's best to split such multiple actions into separate statements;
you don't get any extra credit for complexity of the expression.