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From: tanner@cdis-1.uucp (Dr. T. Andrews)
Newsgroups: comp.lang.c
Subject: Re: sizeof a struc field
Message-ID: <7678@cdis-1.uucp>
Date: 9 Oct 89 14:06:39 GMT
References: <7710@microsoft.UUCP> <11086@smoke.BRL.MIL> <131@dtoa3.dt.navy.mil> <11227@smoke.BRL.MIL>
Organization: Society to Save the Sand Gnat
Lines: 13

In article <11227@smoke.BRL.MIL>, gwyn@smoke.BRL.MIL (Doug Gwyn) writes:
)) ... WHY (((type *)0)->anything) is disallowed in the context
)) of compile-time expressions.
) Because (type *)0 is SYNTACTICALLY a null pointer, and there is a
) prohibition against using a null pointer as the left operand of ->.

It is begging the question to say that "it is disallowed because it
is prohibited".  The sizeof() operator is used to extract type
information, and the cited NULL pointer happens to come complete
with all of the required type information.
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