Re: [Boost-users] null_ptr?

From: Dave Steffen (dgsteffen_at_[hidden])
Date: 2008-01-02 19:29:43

On Wednesday 02 January 2008, Scott McMurray wrote:
> On 02/01/2008, Robert Dailey <rcdailey_at_[hidden]> wrote:
> > Where in the standard does it state that assigning an integral constant
> > to a pointer type is legal? Perhaps there is some more generic rule in
> > the standard to which this concept applies.
>
> 4.10 Pointer conversions [conv.ptr]
> 1)  A null pointer constant is an integral constant expression (5.19)
> rvalue of integer type that evaluates to zero. A null pointer constant
> can be converted to a pointer type; the result is the null pointer
> value of that type and is distinguishable from every other value of
> pointer to object or pointer to function type. Two null pointer values
> of the same type shall compare equal.

  Those interested should check out 
  http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2431.pdf
  "A name for the null pointer: nullptr (revision 4)".  It's not in
  the draft standard yet, but will be soon.  IIRC it also contains an
  excellent discussion of the issues involved.

-- 
Dave Steffen - Software Engineer 4
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