[boost] null (was: singleton design plan)

From: Jason Hise (chaos_at_[hidden])
Date: 2005-07-28 18:59:47

Martin Wille wrote:

>Jason Hise wrote:
>
>>I plan to sneak an improved version of the null developed by Scott 
>>Meyers in with this code in a header called boost/null.hpp, and use it 
>>in the singleton's implementation.  It will be defined as follows:
>>    
>>
>[...]
>
>>undef NULL
>>#define NULL (::boost::null)
>>    
>>
>I violently object to sneaking in something that fundamental.
>  
>
If I was really trying to 'sneak' it in I wouldn't have mentioned it 
explicitly on the list. ;)

>I also object to this idea in general. It doesn't buy us much, it breaks 
>existing code, it may cause ODR violations, and it also violates the C++ 
>Standard.
>
What existing code will it break?  I would imagine it would only break 
code that deserves to be broken in the first place (like int i = NULL).  
Also, how would this cause ODR violations?  I was under the impression 
that the one definition rule required all definitions in different 
translation units to be identical, not that it required that a 
definition only be provided in one translation unit.  And even if 
somehow more than one instance of null ended up being used, how would 
this actually end up causing a problem?  Would your problem with this 
code vanish if I removed the NULL definition on the last two lines?  
Would it reappear if I moved the null class into the global namespace 
(essentially making lowercase null a keyword)?

Please don't take my response as confrontational, I do appreciate the 
feedback.

-Jason