flush in logger

include/spdlog/sinks/base_sink.h

@@ -58,8 +58,6 @@ public:
         _sink_it(msg);
     }
 
-    virtual void flush() = 0;
-
 protected:
     virtual void _sink_it(const details::log_msg& msg) = 0;
     Mutex _mutex;

include/spdlog/sinks/sink.h

@@ -35,6 +35,7 @@ class sink
 public:
     virtual ~sink() {}
     virtual void log(const details::log_msg& msg) = 0;
+    virtual void flush() = 0;
 };
 }
 }

include/spdlog/sinks/syslog_sink.h

@@ -78,6 +78,8 @@ public:
         ::syslog(syslog_prio_from_level(msg), "%s", msg.formatted.str().c_str());
     }
 
+    virtual void flush() override {
+    }
 
 
 private: