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Date: Wed, 9 Jan 2013 21:11:28 +0000
From: Rob <robpilling@...il.com>
To: musl@...ts.openwall.com
Subject: Re: NULL

On Wed, Jan 09, 2013 at 10:36:30AM -0500, Rich Felker wrote:
> i.e. confusion of NULL with ASCII NUL. However, this raises a good
> question: short of C11 _Generic, is it even possible for a program to
> detect whether NULL has integer or pointer type?
>
> I know of one way, but it's very obscure:
>
> int null_is_ptr_type()
> {
> 	char s[1][1+(int)NULL];
> 	int i = 0;
> 	return sizeof s[i++], i;
> }

Magic... is `s' a VLA here? My mind is boggled because
__builtin_constant_p(1+(int)NULL) returns 1, and I can't think of any
reason why the sizeof is evaluated.

Also, seeing that clang and tcc return 0 in all cases, is this a bug in
both of them?

Cheers,
Rob

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