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From: jabir@quintus.uucp (Jabir Hussain)
Newsgroups: comp.lang.c,comp.arch
Subject: Re: Explanation, please!
Message-ID: <339@quintus.UUCP>
Date: 1 Sep 88 20:00:35 GMT
References: <638@paris.ics.uci.edu> <dpmuY#2EBC4R=eric@snark.UUCP> <189@bales.UUCP> <9064@pur-ee.UUCP>
Sender: news@quintus.UUCP
Reply-To: jabir@quintus.UUCP (Jabir Hussain)
Organization: Quintus Computer Systems, Inc.
Lines: 39

In article <9064@pur-ee.UUCP> hankd@pur-ee.UUCP (Hank Dietz) writes:
>	struct t512 { int t[512]; };
>	struct t256 { int t[256]; };
[...]
>	if (n & 512) {
>		*((struct t512 *) q) = *((struct t512 *) p); q+=512; p+=512;
>	}
[...]
>	                      Unfortunately, the above code should have been
>	written as:
>
>	if (n & 512) {
>		*(((struct t512 *) q)++) = *(((struct t512 *) p)++);
>	}
>	...
>
>	but, for some unknown reason, the VAX C compiler didn't like that.


one portable way around that is to do something like:

	typedef char *caddr_t;
	typedef union {
	    struct { int t[512]; } t512;
	    struct { int t[256]; } t256;
	    caddr_t               caddr;
	} ustruct_t;

	{
	    register ustruct_t src,dst;

	    src.caddr = (caddr_t) p;
	    dst.caddr = (caddr_t) q;

	    if (n & 512) *dst.t512++ = *src.t512++;
	    ...
	}

jh