Path: utzoo!utgpu!watmath!datanguay
From: datanguay@watmath.waterloo.edu (David Adrien Tanguay)
Newsgroups: comp.lang.c
Subject: Re: sizeof a struc field
Message-ID: <30488@watmath.waterloo.edu>
Date: 19 Oct 89 10:25:37 GMT
References: <7710@microsoft.UUCP> <11086@smoke.BRL.MIL> <131@dtoa3.dt.navy.mil> <11316@smoke.BRL.MIL> <1234@crdos1.crd.ge.COM>
Reply-To: datanguay@watmath.waterloo.edu (David Adrien Tanguay)
Organization: U. of Waterloo, Ontario
Lines: 26

In article <1234@crdos1.crd.ge.COM> davidsen@crdos1.UUCP (bill davidsen) writes:
]
]Here's what the standard says (3.3.3.4):
]	[quotes the standard]
]
]If the expression is not evaluated the pointer is not dereferenced and
]there is no problem as far as hypothetical hardware which checks for
]this. I see nothing which I can read to forbid the original construct
]or indicate that it might not be valid in this case. The meaning of an
]incomplete type is spelled out in 3.1.2.5 and a null pointer with a
]cast isn't shown. I therefore conclude that the construct of the
]original poster is valid C as specified by the standard.

See also section 3.3.2.3, on the '->' and '.' operators. It eventually
says "...designates a member of a structure or union object." and
"... is an lvalue.". ((struct foo *)0)->elem does not designate an
object. Is there a clearer indication elsewhere?

]I also really
]wonder why sizeof doesn't return "unsigned int" but I suspect i wouldn't
]like the answer.

Unsigned int might not be large enough to hold the size of an object.
E.g., an IBM PC with huge objects.

David Tanguay