Re: [boost] [move][container] Review Request (new versions of Boost.Move and Boost.Container in sandbox and vault)

Subject: Re: [boost] [move][container] Review Request (new versions of Boost.Move and Boost.Container in sandbox and vault)
From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2009-08-24 12:29:09

Frank Mori Hess escribió:
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> On Monday 24 August 2009, Ion Gaztañaga wrote:
>> Thomas Klimpel escribió:
>>> I would say that if an automatic "bad smell" detection tool like
>>> Coverity would flag the above code as dangerous, it wouldn't be
>>> completely wrong. After mx was used via boost::move(mx), it is not
>>> supposed to be used again. So I think it would be better to write
>>>
>>> vector(BOOST_RV_REF(vector) mx) :  base_t(mx) {  this->swap(mx);   }
>>>
>>> which is also less confusing for a human reader.
>> Yes, but that wouldn't be the right thing. When writing move
>> constructors one must first move base classes and then
>> members.
> 
> Yes, but the swap swaps both the base members and derived members.

Ooops! Thanks for spotting this.

> Wouldn't it look less suspicious if base_t were constructed the same way as in 
> the default vector constructor?  In this case moving into the base class 
> can't accomplish anything useful even in principle, since whatever it does 
> will be blown away by the swap.  And if a move constructor were added to 
> base_t (detail::vector_alloc_holder doesn't appear to have one) which 
> modified its moved-from argument, it wouldn't cause bugs.

Yes, default constructor would be right, the problem is that an 
allocator might not have a default constructor. I'll fix this.

Thanks,

Ion