id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
4367,Proposed fix for test_thread_move_return.cpp,sergey.sprogis@…,Anthony Williams,"Bug description:
----------------

The original statement in test_thread_move_return.cpp (Line 16):

  return boost::move(t);

triggered the following error message in Sun C++ compiler (this compiler 
assumes that Boost has fix #4305 for boost/thread/detail/thread.hpp):

============================================
""test_thread_move_return.cpp"", line 16: Error: Cannot use boost::detail::thread_move_t<boost::thread> to initialize boost::thread without ""boost::thread::boost::thread(const boost::thread&)"";.
1 Error(s) detected.
============================================ 

and the same test built with gcc-4.4.4 also failed in a similar way

============================================

test_thread_move_return.cpp: In function 'boost::thread make_thread_move_return(boost::thread::id*)':
test_thread_move_return.cpp:16: error: no matching function for call to 'boost::thread::thread(boost::thread)'
../../../boost/thread/detail/thread.hpp:202: note: candidates are: boost::thread::thread(boost::detail::thread_move_t<boost::thread>)
../../../boost/thread/detail/thread.hpp:150: note:                 boost::thread::thread()
../../../boost/thread/detail/thread.hpp:108: note:                 boost::thread::thread(boost::thread&)
============================================ 

Sun compiler reports the failure because for the following reason.

After finding  user-defined copy constructor in  
boost/thread/detail/thread.hpp  (line 108)  thread(thread&); compiler
does not provide the default copy constructor with  'const' qualifier like
thread(const thread&).

Then later, when compiler processes test's return statement (line 16) 

  return boost::move(t); 

a copy constructor is needed to return the temporary  thread  object by 
value  from  make_thread_move_return(),  but  there  is  no viable copy
constructor. The existing copy constructor cannot be used because  it's
not  allowed  to  bind  an  rvalue  (the  temporary thread object) to a
non-const reference. (Std 2003 13.3.3.1.4:3 )

So, the result is an error message  mentioned above. 

Meantime, after replacing 

return boost::move(t);

with 

return boost::thread(boost::move(t));

compiler does not need copy constructor to create the result object,
only  user-defined   conversion constructor thread(thread_move_t) is
used (Std 2003 8.5/14).
",Bugs,closed,,thread,Boost 1.44.0,Problem,invalid,test_thread_move_return,stephen.clamage@…