Why is std::packaged_task not valid?

Question

Using MSVC2012,

The following code will compile and run as expected

std::packaged_task< int() > task( []()->int{ std::cout << \"hello          


        

Answer 1

This works in gcc 4.7.2:

#include 
#include 
#include 

int main() {
  std::packaged_task< void() > task( [](){ std::cout << "hello world" << std::endl; } );
  std::thread t( std::move(task) );
  t.join();
  std::packaged_task< int() > task2( []()->int{ std::cout << "hello world" << std::endl; return 0; } );
  std::thread t2( std::move(task2) );
  t2.join();
}  

Together with @WhozCraig 's archeology implies that this is probably a bug in MSVC2012.

For a workaround, try using struct Nothing {}; or nullptr_t as your return value?