id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
2570	boost::interprocess::message_queue::timed_send and timed_receive bug	Tony Astolfi <aastolfi@…>	Ion Gaztañaga	"In boost::interprocess::message_queue, the timed_send and timed_receive methods may return true without actually performing the send or receive operation.

The problem lies in boost/interprocess/ipc/message_queue.hpp, in the logic that handles blocking behavior for these two methods.  Both implementations have the same form:

if (<operation-would-block>) {
  switch(block){  
    ...  
    case timed :
    do{
      if(!<condition-variable>.timed_wait(lock, abs_time))
        return !<operation-would-block>;
    }
    while (<operation-would-block>);
    break;
    ...
  }
}

The problem is that when timed_wait returns false, it might be possible to complete the operation without blocking (i.e. there might be something in the queue in the case of receive, or the queue might not be full in the case of send).  Therefore, in rare cases, timed_send/timed_receive return true, without having actually done any work.

My proposed fix is to change the timed case to:

    do{
      if(!<condition-variable>.timed_wait(lock, abs_time)) {
        if(<operation-would-block>) {
          return false;
        }
        break;
      }
    }
    while (<operation-would-block>);

After I apply this change to my own boost install, the problem disappears.

I observed this bug on Linux (some Debian 4 flavor, 32-bit)
"	Bugs	closed	Boost 1.38.0	interprocess	Boost 1.37.0	Showstopper	fixed