SObjectizer is one of the cross-platform and open-source actor frameworks
for C++, yet it supports not only Actor Model, but also Publish-Subscribe
Model and CSP-like channels.  The goal of SObjectizer is to significantly
simplify development of concurrent and multithreaded applications in C++.

SObjectizer allows to create a concurrent application as a set of agent-
objects which interact with each other through asynchronous messages.
It handles message dispatching and provides a working context for message
processing, and allows to tune those things by supplying various ready-
to-use dispatchers.