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From: Rob Landley <rob@landley.net>
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Subject: Re: NULL
Date: Fri, 11 Jan 2013 23:56:02 -0600
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On 01/09/2013 05:02:29 AM, John Spencer wrote:
> glibc defines NULL as __null: a magic variable supplied by GCC and =20
> compatibles which always has pointer context.
>=20
> musl defines NULL to 0 in C++.
> this is correct per the standard, but breaks a lot of software on =20
> 64bit archs,
> because it promotes to int.

The C99 standard section 7.17 defines the NULL macro as:

   expands to an implementation-defined null pointer constant

Which means it has pointer type. So either we can typecast it to void =20
*, or we can rely on the LP64 standard (Linux, FreeBSD, and macosX all =20
support) which says that long and pointer are always the same size on =20
both 32 bit and 64 bit, so trivial fix would be #define NULL to (0L)

   http://www.unix.org/whitepapers/64bit.html

Rob=