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From: gwyn@smoke.BRL.MIL (Doug Gwyn)
Newsgroups: comp.lang.c
Subject: Re: sizeof a struc field
Message-ID: <11120@smoke.BRL.MIL>
Date: 20 Sep 89 19:39:31 GMT
References: <7710@microsoft.UUCP> <11086@smoke.BRL.MIL> <131@dtoa3.dt.navy.mil> <11110@smoke.BRL.MIL> <8361@ardent.UUCP>
Reply-To: gwyn@brl.arpa (Doug Gwyn)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 14

In article <8361@ardent.UUCP> jss@jra.ardent.com (Jerry Schwarz (Compiler)) writes:
-With regard to a discussion of:
-	sizeof(((struct abc *)0)->ghi)
-Which suggests that Doug believes that this is an illegal expression.  
-But is it?  It (the operand of sizeof) is an expression whose evaluation 
-would result in undefined behavior, but does that make it illegal? 
-I think not, and here it is used in a context where it explicitly will 
-not be evaluated.

(((struct abc *)0)->ghi) is not a valid unary expression,
because the left-hand operand of the -> is not an lvalue
that points at an object (see 3.3.2.3 Semantics).

This has nothing to do with evaluation.