Re: Newbie boost::thread question

From: bill_kempf (williamkempf_at_[hidden])
Date: 2002-09-17 13:00:57

--- In Boost-Users_at_y..., Luis De la Parra <lparrab_at_g...> wrote:
> On Monday 16 September 2002 16:50, Marcio Del'Valle wrote:
> >  Hi there,
> >
> > When I use boost::thread for creating multiple threads I notice 
that the
> >  destructor of object I pass as an argument ( boost::thread
(*pObjetc) ) is
> >  called twice. Why does it happen?
> 
> because boost makes a copy (acutally several!!) of the object, and 
then 
> destroys them. boost calls the copy constructor to get a copy of 
the object 
> you pass as a function object, and then makes another copy (don't 
know why)  
> and then destroyes the "temporary" objects.

This is documented.  The number of copies made is left to the 
implementation, but generally should be kept to a minimum.  If you 
don't want "pass by value" semantics use a wrapper/adapter such as 
boost::ref.

Bill Kempf