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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

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