Re: [boost] Boost.Threads, N2178, N2184, et al

From: Howard Hinnant (hinnant_at_[hidden])
Date: 2007-03-26 15:14:45

On Mar 26, 2007, at 2:47 PM, Peter Dimov wrote:

> But my question is more along the lines of: why does the const/non- 
> const
> label matter when we decide on the precondition and thread safety of
> t.cancel? If t.cancel is always valid on a valid t, this makes sharing
> possible and safe, regardless of whether thread::cancel is declared  
> const.

I guess my answer would go back to this snippet:

void foo(const thread& t);

void bar()
{
     std::thread t(f);
     ...
     foo(t);
     ...
}

Because of the const qualifier on the thread& which foo takes as a  
parameter, and knowing that the const interface of thread is a subset  
of the non-const interface, we can make useful assumptions about t  
after the call to foo() (such as t hasn't been canceled).  This might  
be particularly helpful if foo is a virtual function.

-Howard