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Re: proposal: stricter type-checking for macros

From: Han-Wen Nienhuys
Subject: Re: proposal: stricter type-checking for macros
Date: Thu, 25 Mar 2004 16:34:54 +0100

address@hidden writes:
> Han-Wen Nienhuys  <address@hidden> 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   |   address@hidden   | 

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