[boost] Re: shifted_ptr review

From: David Abrahams (dave_at_[hidden])
Date: 2003-10-01 10:52:32

Gregory Colvin <gregory.colvin_at_[hidden]> writes:

> Still wondering.
>
> On Tuesday, Sep 30, 2003, at 11:09 America/Denver, Gregory Colvin wrote:
>> Given
>>
>>   template<typename T> shifted_ptr<T> make_shifted_ptr(cont T& t) {
>>       return shifted_ptr(new(so) T(t));
>>   }
>>
>>   ... make_shifted_ptr(Stuff()) ...
>>
>> are compilers allowed to optimize away the copy and construct the
>> Stuff in place?

The copy of the shifted_ptr?  Yes, of course.  That's the RVO.

>> If so, do they?

Some do; some don't.

Oh, wait.  You meant the copy of Stuff()?  It's not meant to be a T
neccessarily.  It's just any old argument to T's constructor.  You
need a bunch of overloads for make_shifted_ptr to make the example
complete.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com