Boost::Thread

1 Sep 2008

      I've been trying to use boost::thread with a movable structure (see end 
for code + error). From the online manual ( 
http://www.boost.org/doc/libs/1_36_0/doc/html/thread/thread_management.html#... 
)

	template <class F, class A1, class A2, ...>

	thread(F f, A1 a1, A2 a2, ...);

	Preconditions:
		F and each An must by copyable or movable.

	Effects:
        	As if thread(boost::bind(f,a1,a2,...)). Consequently, f and 
each an are copied into internal storage for access by the new thread.

I've been running into a problem with this however. The use of 
boost::bind means that F needs to have a copy constructor, which seems 
odd as the manual says "or movable".
Am I doing something wrong, or is this an oversight, or what?

Regards,
Daryl.

----------
Code:
(built with: gcc version 4.4.0 20080831 (experimental) (GCC)
             g++-trunk -o move_thread move_thread.cpp --std=c++0x 
/usr/local/lib/libboost_thread-gcc43-mt.a)
----------
#include <iostream>
#include <vector>
#include <boost/preprocessor/iteration/iterate.hpp>
#include <boost/thread.hpp>

using std::cout;
using std::endl;
using std::vector;
using boost::thread;

struct S
{
  S(int)  { cout << "S()"      << endl; }
  S(S &&) { cout << "S() move" << endl; }

  void operator()(int i) { cout << "Thread running [" << i << "]" << endl; }

  S(S const &) = delete;
};

int main()
{
  vector<thread> v;
  for (int i = 0; i < 10; ++i)
  {
    v.push_back(thread(S(i), i));
  }

  for (int i = 0; i < 10; ++i)
  {
    v[i].join();
  }
}

----------
Error:
----------
In file included from /usr/local/include/boost/thread/thread.hpp:22,
                 from /usr/local/include/boost/thread.hpp:13,
                 from move_thread.cpp:4:
move_thread.cpp: In constructor ‘boost::thread::thread(F, A1) [with F = 
S, A1 = int]’:
move_thread.cpp:26:   instantiated from here
move_thread.cpp:18: error: deleted function ‘S::S(const S&)’
/usr/local/include/boost/thread/detail/thread.hpp:227: error: used here
/usr/local/include/boost/thread/detail/thread.hpp:227: error: 
initializing argument 2 of ‘boost::_bi::bind_t<R, F, typename 
boost::_bi::list_av_1<A1>::type> boost::bind(boost::type<R>, F, A1) 
[with R = void, F = S, A1 = int]’

Daryl Haresign

Peter Dimov

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