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To: eivind@dimaga.com
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Subject: Re: NULL as ((void*)0) (was Re: strlen() question) 
In-Reply-To: Your message of "Sat, 15 Feb 1997 01:48:58 +0100"
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Date: Sat, 15 Feb 1997 11:26:39 +0100
From: "Arne H. Juul" <Arne.Juul@idt.ntnu.no>
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> BTW: I just got another idea - if we can turn the definition of NULL
> between ((void*)0) and 0 we can detect if NULL is abused if compiling on a
> machine with different sizeof(void*) and sizeof(int).  If used correctly,
> code will be equal no matter what the definition - if used incorrectly,
> different code should result.  This can provide fairly automatic detection
> of errors, provided we have two different builds.

I think this is a good idea too, but it isn't really neccessary
to change anything in the main source tree for this (though it
would make it easier if there was just one place to change, of
course).  I have done a make world with (most) of the #define's
for NULL set to ((void *)0) and have found a few minor bugs
already (23% done).  PR will follow.

BTW, as far as I can see from my C standard the rules for NULL
are pretty lax; both (1-1) and something like
	typedef enum { __ournull=0 } __dummynull;
	#define NULL __ournull
should be legal.

  -  Arne H. J.