Re: [Boost-users] boost::thread() calls destructor!!

From: Patrik Jonsson (patrik_at_[hidden])
Date: 2005-05-28 11:00:03

Hi,

I don't pretend to know how the boost thread functions work, but I've 
used them and haven't had any problems. Are you sure it's not just that 
the object is being copied 4 times and what you're seeing are the 
destructors for the copies? In your test code, you wouldn't be able to 
tell.  According to the docs, the thread constructor makes at least one 
copy of its argument. Does your class have a working copy constructor?

cheers,

/Patrik

Ricky Corsi wrote:

> Hello,
>
> I tried to modify the sample code from Bill Kempf for boost.thread,
> listing 4 that I got at the following link
> http://www.cuj.com/documents/s=8470/cuj0205kempf/list4.htm
>
> to embed the write function in a writeClass function-object.
> That is a test because in a program I need to pass a function object to
> one thread, and not a global function.
>
> I simply wrote this code:
>
> class writerClass
> {
> public:
>     ~writerClass()
>     {
>         // for Debug
>         std::cout << "writerClass dtor" << std::endl;
>     }
>
>     void operator() ()
>     {
>         for (int n = 0; n < ITERS; ++n)
>         {
>             {
>                 boost::mutex::scoped_lock
>                     lock(io_mutex);
>                 std::cout << "sending: "
>                     << n << std::endl;
>             }
>             buf.put(n);
>         }
>     }
> };
>
> and changed in the main()
> --> boost::thread thrd2(&writer);
> with
> --> boost::thread thrd2((writerClass()));
>
> Everything works the same, but I have the destructor of wirterClass
> called 4 times, when constructing thrd2!!!
>
> That's weird to me, but it's annoying because in my other program, the
> dtor destroys some member data, and the program crashes because of it.
> Why is the ~writerClass() called?
> is there maybe some exception thrown??
> how can I solve the problem?
>
> thank you
> ricky
>
>
> P.S.
> if it can be useful, during the compilation I get a warning (MSVC 7.1),
> but I read that it can be safely ignored:
>
> warning C4275:
> non dll interface class "boost::noncopyable_::noncopyable"
> used as a base for dll interface class "boost::mutex"
>
> [...]\boost\noncopyable.hpp(22): see declaration of
> "boost::noncopyable_::noncopyable"
> [...]\boost\thread\mutex.hpp(33): see declaration of "boost::mutex"
>
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