Re: [boost] [Boost.Pool] TR1?

Subject: Re: [boost] [Boost.Pool] TR1?
From: Jeremy Maitin-Shepard (jeremy_at_[hidden])
Date: 2011-04-13 14:00:29

On 04/13/2011 10:40 AM, Dave Abrahams wrote:
> On Wed, Apr 13, 2011 at 1:32 PM, Anders Dalvander<boost_at_[hidden]>  wrote:
>> On 20:59, Nevin Liber wrote:
>>>
>>> While the undefined behavior goes away, all that std::less guarantees is a
>>> total ordering for pointers.  It doesn't specify what that ordering
>>> actually
>>> is.
>>
>> True, the actual order isn't defined. But I don't see the issue.
>>
>> Externally a contiguous memory block would be seen as a singleton and
>> comparing it using std::less to any other contiguous memory block would
>> result in either true or false.
>
> The issue is that if you test an address for being within a given
> memory block, you can get false positives.
>
> Oh, and to make things worse, IIRC there's nothing that says a<  b ==
> std::less<...>()(a,b) even within a given block, e.g.
> std::less<>()(a,b) could be implemented as a>  b!  So you can get
> false negatives, too.

Perhaps the real question is whether there exists a C++ compiler that we 
care about this working on that doesn't behave as we'd like.

Not everything left undefined by the standard was necessarily a good 
decision.