Re: [boost] movable threads, locks, and boost::array

From: Anthony Williams (anthony.ajw_at_[hidden])
Date: 2008-05-27 18:02:07

Sohail Somani <sohail_at_[hidden]> writes:

> David Abrahams wrote:
>> I just discovered that while none of my standard containers are
>> "move-aware" in the way needed by boost::thread, I can use boost::array
>> to store threads by simply move-assigning new threads into the elements
>> it contains:
>> 
>>    boost::array<boost::thread, 100> thread_q;
>> 
>>    for (int i = 0; i < 100; ++i)
>>        thread_q[i] = boost::thread( some_function );
>> 
>> it ain't perfect, but given that the number of cores on any real machine
>> is limited these days, you can do a lot with a fixed-size array of
>> thread.  Pretty cool; it sure beats using shared_ptr.
>
> Why doesn't it require std::move or boost::move? I thought this was 
> required to move anything. Looks like there is some sort of conversion 
> operator.

You only need std::move or boost::move to move an lvalue. If you've
got an rvalue (such as the temporary in Dave's example),
move-assignment "just works" in most cases.

In boost 1.35.0 this is done with a move-emulation trick involving
conversions to boost::detail::thread_move_t<>, but on trunk it uses
rvalue references if the compiler supports it.

Anthony
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