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From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: comp.lang.c
Subject: Re: Determing alignment of (char *) pointer
Message-ID: <7388@utzoo.UUCP>
Date: Sat, 6-Dec-86 20:45:38 EST
Article-I.D.: utzoo.7388
Posted: Sat Dec  6 20:45:38 1986
Date-Received: Sat, 6-Dec-86 20:45:38 EST
References: <1510@mit-trillian.MIT.EDU>, <487@cartan.Berkeley.EDU>
Organization: U of Toronto Zoology
Lines: 15

> 	if (p != (char *) (long *) p) ... ?
>    This should give you the relevant information (can a long be stored at
> the location pointed to by p?) without any machine dependencies.  I suppose
> on some (broken) compilers it might not work...

Also on some non-broken compilers, alas.  Converting "char *" to "long *"
with a cast does not guarantee that the result is a VALID "long *".  That
is your problem, not the compiler's.  On some machines this will work,
because the conversion involves a change in representation, explicitly
dropping the higher-precision part of the char pointer.  But on orthodox
machines like VAXen and 68Ks, the compiler makes no attempt to clear those
nasty low-order bits, so the comparison tells you nothing.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,decvax,pyramid}!utzoo!henry