Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uunet!crdgw1!underdog!volpe
From: volpe@underdog.crd.ge.com (Christopher R Volpe)
Newsgroups: comp.lang.c
Subject: Double typecast in "offset" macro???
Message-ID: <8242@crdgw1.crd.ge.com>
Date: 6 Jun 90 14:27:24 GMT
Sender: news@crdgw1.crd.ge.com
Distribution: usa
Organization: General Electric Corporate R&D Center
Lines: 13

In the "Answers to Frequently Asked Questions" document,
the structure offset macro is defined as follows:

#define offset(type,mem) ((size_t) (char *)&(((type *)0)->mem))

Now, the "&" operator yields a pointer to the type of "mem".
If you want to convert it to be of type "size_t", why must it
first be converted to "char *" ??  What's wrong with the following:

#define offset(type,mem) ((size_t) &(((type *)0)->mem))

Thanks,
Chris