...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
boost::log::sinks::synchronized_feeding
// In header: <boost/log/sinks/frontend_requirements.hpp> struct synchronized_feeding { };
The sink backend expects pre-synchronized calls, all needed synchronization is implemented in the frontend (IOW, only one thread is feeding records to the backend concurrently, but it is possible for several threads to write sequentially). Note that if a frontend supports synchronized record feeding, it will also report capable of concurrent record feeding.