Re: private types

["Dr. Adrian Wrigley" <amtw@linuxchip.demon.co.uk.uk.uk>]

On Sun, 19 Mar 2006 20:20:52 +0100, Martin Krischik wrote:

> Robert A Duff wrote:
> 
>> I believe the C++ rule is that 0 (written in your program) is the same
>> thing as NULL -- but it need not be represented internally by
>> all-zero-bits. �Casting the integer zero to a pointer, however, 
>> does not necessarily result in NULL. �That's sort of confusing,
>> but if you understand the rules, the "quite challenging" comment
>> above does not hold.
> 
> Super! And how many (in %) of C++ programmer actually know that. By guess is
> 0.1%. And indeed I is the main problem: Only a very few C/C++ programmers
> actually master the language. 

It is (or was) quite a common interview question, to see if
C (and C++) programmers know their subject properly.  As you
say, Robert, most don't.

A related topic is the issue of pointer representation, which
(IIRC) says that pointers to char (any kind) and void have to be
the same.  Pointers to functions have to be the same.  But all
other pointers can have their own representation.  All pointers
can be converted to and from pointers to void, without loss.  And
pointers can have different sizes and different patterns for the
null pointer.  I suspect a lot of code would fail if compilers
wanted to exercise their full freedoms!
--
Adrian