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That's what I thought, until I stumbled onto this article:

The problem arises when varargs are used, so lua might (haven't checked) not be hitting the issue.

Take this example, from the article:

               XtNx, -1000,
               XtNy, -1000,
               XtNwidth, 100,
               XtNheight, 100,
               XtNmappedWhenManaged, False,

The 0 at the end is supposed to be NULL.

In 32-bit code everything is okay, but in 64-bit code, 0 is still 32-bits (for certain compilers), and the function instead of receiving NULL receives something else.

It's just a pitfall to be aware, in other contexts I guess one can freely replace NULL with 0 (until someone else discover problem with that).

On 12/1/11 1:51 AM, Miles Bader wrote:
Enrico Colombini<>  writes:
"0" should be perfectly acceptable in a pointer context; this sounds
like a bug with the C compiler...

That's in C++.

It's acceptable in both C and C++.

In C, if I remember correctly, there is no automatic conversion and
the integer/pointer types could be incompatible on some hardware.

You remember incorrectly.  Both C and C++ will automatically do the
implicit conversion of a "0" in the source code to the appropriate
pointer type in a pointer context.

Remember, we're talking about "0" in the source code, not a run-time
value of zero; a NULL pointer may indeed have a non-zero value at