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: Christopher Jefferson (chris_at_[hidden])
Date: 2009-09-07 15:26:09

On 7 Sep 2009, at 20:08, Jeffrey Hellrung wrote:

> Howard Hinnant wrote:
>> Using an experimental C++0x compiler and library (you might can do  
>> this experiment g++-4.4, I'm not sure) I make this substitution and  
>> indeed, I get the same output (remove all of the *.dat files prior  
>> to each run).  This experimental library has:
>> template <class _Tp, class _Allocator>
>> inline
>> vector<_Tp, _Allocator>&
>> vector<_Tp, _Allocator>::operator=(vector&& __x)
>> {
>>    clear();
>>    swap(__x);
>>    return *this;
>> }
>
> Perhaps a dumb question, but isn't the above incorrect under self- 
> assigment (x = move(x))?  Is there a "standard way" or "recommended  
> guideline" for handling self-assignment in the move assignment  
> operator, or is this a nonissue?

I'm actually not 100% positive what the intended semantics of x = move 
(x) are, but clearly as a QOI issue it should behave.

Most people put:

if(&__x != this)

or something similar in normal assignment operators, adding it also to  
all move operators seems very sensible.

Chris