Short story

Use -fpch-preprocess option alongside with -c option in order to make precompiled headers work properly.

Update: I asked the same question on the gcc help mailing list and Ian Lance Taylor explained this strange behavior by my usage of distcc/ccache. These tools first preprocess the source that’s why this options is required.

Long story

I’m using gcc-4.4.1 on Linux and before trying precompiled headers in a really large project I decided to test them on a simple program. They “kinda work” but I was not happy with results and I was sure there was something wrong about my setup.
(more…)

Here is a small C++ function which allows you to submit async jobs into the thread pool and track their execution status using the concept of futures:

#include "boost/threadpool.hpp"
#include "boost/future.hpp"
#include "boost/utility/result_of.hpp"
#include "boost/shared_ptr.hpp"
 
template<typename Thp, typename Func>
boost::shared_future< typename boost::result_of<Func()>::type >
submit_job(Thp& thp, Func f)
{
  typedef typename boost::result_of<Func()>::type result;
  typedef boost::packaged_task<result> packaged_task;
  typedef boost::shared_ptr<boost::packaged_task<result> > packaged_task_ptr;
 
  packaged_task_ptr task(new packaged_task(f));
  boost::shared_future<result> res(task->get_future());
  boost::threadpool::schedule(thp, boost::bind(&packaged_task::operator(), task));
 
  return res;
}

A typical example of its possible usage:

User lookup_user_in_database(int id) { ... }
...
int main()
{
  boost::threadpool::pool thp(3);//number of threads
  boost::shared_future<User> future = 
    submit_job(boost::bind(lookup_user_in_database, 10));
  while(!future.is_ready())
  { 
  //do something useful
  }
  User = future.get();
  ...
}

boost::futures are now finally officially shipped with boost starting with 1.41 release. boost::threadpool is not yet an official boost library, however you can find it here.

Much kudos to authors of these amazing libraries!