Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!iuvax!cica!tut.cis.ohio-state.edu!cs.utexas.edu!usc!snorkelwacker!spdcc!ima!haddock!karl
From: karl@haddock.ima.isc.com (Karl Heuer)
Newsgroups: comp.lang.c
Subject: Re: Generic Swap
Keywords: swap
Message-ID: <16864@haddock.ima.isc.com>
Date: 13 Jun 90 02:07:41 GMT
References: <1990Jun11.133729.6575@cs.utk.edu> <16846@haddock.ima.isc.com> <1990Jun11.214844.21531@agate.berkeley.edu>
Reply-To: karl@haddock.ima.isc.com (Karl Heuer)
Distribution: usa
Organization: Interactive Systems, Cambridge, MA 02138-5302
Lines: 17

In article <1990Jun11.214844.21531@agate.berkeley.edu> dankg@sandstorm.Berkeley.EDU (Dan KoGai) writes:
>void *temp;
>#define swap(type, x, y) temp = (type *)malloc(sizeof(type));\
>	*(type)temp = x; x = y ; y = *(type)temp; free(temp)

Those casts don't make sense.  I think you want
	#define swap(type, x, y) temp = malloc(sizeof(type));\
	*(type *)temp = x; x = y ; y = *(type *)temp; free(temp)

>	Since this is a macro, it should work even though your compiler
>does not allow passing structs as arguments (struct assignment is valid
>since K&R while struct as argument is not).

Wrong.  The three forms of struct copy (assignment, pass by value, return by
value) were all added at the same time, shortly after K&R 1 was published.

Karl W. Z. Heuer (karl@ima.ima.isc.com or harvard!ima!karl), The Walking Lint