On Monday 26 April 2004 09:53 am, David Abrahams wrote:
So, we're thinking of using the signals library in one of our projects, but the lack of thread-safety is a concern for us. What issues are preventing Boost.Signals from being made threadsafe?
The biggest issue is granularity. Do we use signal-level locking or connection/slot-level locking? The former requires few locks, but constrains the coding style quite a bit, whereas the latter is going to incur a bit of overhead (a lock for every slot call, disconnect, etc.). The other issue is correctness w.r.t. deletion of trackable objects, especially when dealing with the slot call iterators: for instance, consider a simple combiner that does this: while (first != last) *first++; If that "++" happens and first != last is true (because there are more slots to call), then another thread disconnects all of the signals from first up to last, then the dereference operator is Bad News. I'm sure there are more issues, but that's a start. Doug