From: Han-Wen Nienhuys <hanwen@xs4all.nl>
Cc: guile-devel@gnu.org
Subject: Re: proposal: stricter type-checking for macros
Date: Thu, 25 Mar 2004 16:34:54 +0100 [thread overview]
Message-ID: <16482.64542.175708.694774@localhost.localdomain> (raw)
In-Reply-To: <m31xnhvtdj.fsf@multivac.cwru.edu>
prj@po.cwru.edu writes:
> Han-Wen Nienhuys <hanwen@xs4all.nl> wrote:
> > // #define TYPECHECK(x) (global_object = (x))
>
> #define TYPECHECK(x) (0? (void)(*(SCM*)0=(x)): (void)0)
>
> Casting to void ensures that the resulting "value" won't accidentally
> be used for anything. "0?" ensures that the null pointer won't
> actually be dereferenced. I'd expect dead-code elimination to compile
> this into nothing, but I haven't checked which optimization level this
> happens for.
Very clever!
I vote for
#define TYPECHECKED(x) (0? (*(SCM*)0=(x)): x)
which returns x, and obviates the void casting.
--
Han-Wen Nienhuys | hanwen@xs4all.nl | http://www.xs4all.nl/~hanwen
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next prev parent reply other threads:[~2004-03-25 15:34 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-03-25 12:23 proposal: stricter type-checking for macros Han-Wen Nienhuys
2004-03-25 15:27 ` Paul Jarc
2004-03-25 15:34 ` Han-Wen Nienhuys [this message]
2004-04-24 22:09 ` Marius Vollmer
2004-04-24 22:54 ` Han-Wen Nienhuys
2004-04-24 23:42 ` Marius Vollmer
2004-03-31 23:08 ` Paul Jarc
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