Added "clone()" support to loggers

example/example.cpp

@@ -18,6 +18,7 @@ void multi_sink_example();
 void user_defined_example();
 void err_handler_example();
 void syslog_example();
+void clone_example();
 
 #include "spdlog/spdlog.h"
 
@@ -34,6 +35,8 @@ int main(int, char *[])
         rotating_example();
         daily_example();
 
+        clone_example();
+
         // async logging using a backing thread pool
         async_example();
 
@@ -56,7 +59,7 @@ int main(int, char *[])
         // release any threads created by spdlog, and drop all loggers in the registry.
         spdlog::shutdown();
     }
-    // Exceptions will only be thrown upon failed logger or sink construction (not during logging)
+        // Exceptions will only be thrown upon failed logger or sink construction (not during logging)
     catch (const spdlog::spdlog_ex &ex)
     {
         std::cout << "Log init failed: " << ex.what() << std::endl;
@@ -122,6 +125,14 @@ void daily_example()
     auto daily_logger = spdlog::daily_logger_mt("daily_logger", "logs/daily.txt", 2, 30);
 }
 
+// clone a logger and give it new name.
+// Useful for creating component/subsystem loggers from some "root" logger
+void clone_example()
+{
+    auto network_logger = spdlog::get("console")->clone("network");
+    network_logger->info("Logging network stuff..");
+}
+
 #include "spdlog/async.h"
 void async_example()
 {

include/spdlog/async_logger.h

@@ -55,6 +55,8 @@ public:
     async_logger(std::string logger_name, sink_ptr single_sink, std::weak_ptr<details::thread_pool> tp,
         async_overflow_policy overflow_policy = async_overflow_policy::block);
 
+    std::shared_ptr<logger> clone(std::string new_name) override;
+
 protected:
     void sink_it_(details::log_msg &msg) override;
     void flush_() override;

include/spdlog/details/async_logger_impl.h

@@ -98,3 +98,17 @@ inline void spdlog::async_logger::backend_flush_()
     }
     SPDLOG_CATCH_AND_HANDLE
 }
+
+
+inline std::shared_ptr<spdlog::logger> spdlog::async_logger::clone(std::string new_name)
+{
+    auto cloned = std::make_shared<spdlog::async_logger>(std::move(new_name),
+                                                         sinks_.begin(), sinks_.end(),
+                                                         thread_pool_,
+                                                         overflow_policy_);
+
+    cloned->set_level(this->level());
+    cloned->flush_on(this->flush_level());
+    cloned->set_error_handler(this->error_handler());
+    return std::move(cloned);
+}

include/spdlog/details/logger_impl.h

@@ -271,6 +271,12 @@ inline void spdlog::logger::flush_on(level::level_enum log_level)
     flush_level_.store(log_level);
 }
 
+inline spdlog::level::level_enum spdlog::logger::flush_level() const
+{
+    return static_cast<spdlog::level::level_enum>(flush_level_.load(std::memory_order_relaxed));
+}
+
+
 inline bool spdlog::logger::should_flush_(const details::log_msg &msg)
 {
     auto flush_level = flush_level_.load(std::memory_order_relaxed);
@@ -346,3 +352,12 @@ inline std::vector<spdlog::sink_ptr> &spdlog::logger::sinks()
 {
     return sinks_;
 }
+
+inline std::shared_ptr<spdlog::logger> spdlog::logger::clone(std::string logger_name)
+{
+    auto cloned = std::make_shared<spdlog::logger>(std::move(logger_name), sinks_.begin(), sinks_.end());
+    cloned->set_level(this->level());
+    cloned->flush_on(this->flush_level());
+    cloned->set_error_handler(this->error_handler());
+    return std::move(cloned);
+}

include/spdlog/logger.h

@@ -115,21 +115,28 @@ public:
     level::level_enum level() const;
     const std::string &name() const;
 
+
     // set formatting for the sinks in this logger.
     // each sink will get a seperate instance of the formatter object.
     void set_formatter(std::unique_ptr<formatter> formatter);
     void set_pattern(std::string pattern, pattern_time_type time_type = pattern_time_type::local);
 
+    // flush functions
     void flush();
     void flush_on(level::level_enum log_level);
+    level::level_enum flush_level() const;
 
+    // sinks
     const std::vector<sink_ptr> &sinks() const;
-
     std::vector<sink_ptr> &sinks();
 
+    // error handler
     void set_error_handler(log_err_handler err_handler);
     log_err_handler error_handler();
 
+    // create new logger with same sinks and configuration.
+    virtual std::shared_ptr<logger> clone(std::string logger_name);
+
 protected:
     virtual void sink_it_(details::log_msg &msg);
     virtual void flush_();