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From: geacc022%timevx@cit-hamlet.arpa
Newsgroups: net.lang.c
Subject: Casting call
Message-ID: <10784@brl-tgr.ARPA>
Date: Fri, 17-May-85 11:45:41 EDT
Article-I.D.: brl-tgr.10784
Posted: Fri May 17 11:45:41 1985
Date-Received: Sun, 19-May-85 00:28:03 EDT
Sender: news@brl-tgr.ARPA
Lines: 22

>This discussion has brought up another point -- somebody posted an example
>where he casted a lhs, and somebody pointed out that you can't do that.
>What I am wondering is, why can't you? There seem to be no semantic problems
>involved, and it can be very useful for something like:
>
>#define FREE(ptr)	 free(char *) ptr); (char *) (ptr) = (char *) -1;

There are indeed problems with this.  What if you're on a machine
where char * is 32 bits, but int * is only 16 bits?

What you really want is a "typeof" operator:

#define FREE(ptr)     {  free((char *) ptr); ptr = (typeof ptr) NULL;  }

Unfortunately, this doesn't exist either.  :-(

			Gary Ansok
			GEACC022%TIMEVX @ CIT-HAMLET.ARPA
			GEA @ CALTECH.BITNET
			...ucbvax!cithep!timevx#geacc022

"All the world loves a straight man."