2009 Jul 29 - Wed

A Singleton Per Thread

A while ago, I had written about singletons, and how there isn't something straight-forward in Boost. Recently, I've seen references to a couple of interesting messages regarding not only singletons, but how to get a singleton per thread.

One starts by considering Boost Thread Local Storage and how to use it.

Then one can consider the concept of a thread-safe lazy singleton template class from the Boost Cookbook, which a singleton implementation not referenced in my other article.

Rutger ter Borg suggested the following untested possible code snippet:

template< typename Singleton >
Singleton& get_singleton() {
  static boost::thread_specific_ptr< Singleton > m_singleton;
  if ( !m_singleton.get() ) {
    m_singleton.reset( new Singleton() );
  }
  return *m_singleton;
}