Function log_debug

include/ai/logger.h:129–131

// Fall back to the atomic shared_ptr free functions on standard libraries
// that have not implemented std::atomic<std::shared_ptr> (notably libc++).

inline std::shared_ptr<Logger>& logger_instance() {
  static std::shared_ptr<Logger> instance = std::make_shared<ConsoleLogger>();
  return instance;
}