Fixed issue #527

include/spdlog/details/async_logger_impl.h

@@ -88,7 +88,7 @@ inline void spdlog::async_logger::_sink_it(details::log_msg& msg)
     try
     {
 #if defined(SPDLOG_ENABLE_MESSAGE_COUNTER)
-        msg.msg_id = _msg_counter.fetch_add(1, std::memory_order_relaxed);
+        _incr_msg_counter(msg);
 #endif
         _async_log_helper->log(msg);
         if (_should_flush_on(msg))

include/spdlog/details/logger_impl.h

@@ -512,7 +512,7 @@ inline bool spdlog::logger::should_log(spdlog::level::level_enum msg_level) cons
 inline void spdlog::logger::_sink_it(details::log_msg& msg)
 {
 #if defined(SPDLOG_ENABLE_MESSAGE_COUNTER)
-    msg.msg_id = _msg_counter.fetch_add(1, std::memory_order_relaxed);
+    _incr_msg_counter(msg);
 #endif
     _formatter->format(msg);
     for (auto &sink : _sinks)
@@ -562,6 +562,11 @@ inline bool spdlog::logger::_should_flush_on(const details::log_msg &msg)
     return (msg.level >= flush_level) && (msg.level != level::off);
 }
 
+inline void spdlog::logger::_incr_msg_counter(details::log_msg &msg)
+{
+    msg.msg_id = _msg_counter.fetch_add(1, std::memory_order_relaxed);
+}
+
 inline const std::vector<spdlog::sink_ptr>& spdlog::logger::sinks() const
 {
     return _sinks;

include/spdlog/details/pattern_formatter_impl.h

@@ -384,6 +384,14 @@ class pid_formatter SPDLOG_FINAL:public flag_formatter
     }
 };
 
+// message counter formatter
+class i_formatter SPDLOG_FINAL :public flag_formatter
+{
+    void format(details::log_msg& msg, const std::tm& tm_time) override
+    {
+        msg.formatted << fmt::pad(msg.msg_id, 6, '0');
+    }
+};
 
 class v_formatter SPDLOG_FINAL:public flag_formatter
 {
@@ -641,11 +649,10 @@ inline void spdlog::pattern_formatter::handle_flag(char flag)
         _formatters.push_back(std::unique_ptr<details::flag_formatter>(new details::pid_formatter()));
         break;
 
-#if defined(SPDLOG_ENABLE_MESSAGE_COUNTER)
+
     case ('i'):
         _formatters.push_back(std::unique_ptr<details::flag_formatter>(new details::i_formatter()));
         break;
-#endif
 
     default: //Unknown flag appears as is
         _formatters.push_back(std::unique_ptr<details::flag_formatter>(new details::ch_formatter('%')));

include/spdlog/logger.h

@@ -118,6 +118,9 @@ protected:
     // return true if the given message level should trigger a flush
     bool _should_flush_on(const details::log_msg&);
 
+    // increment the message count (only if defined(SPDLOG_ENABLE_MESSAGE_COUNTER))
+    void _incr_msg_counter(details::log_msg &msg);
+
     const std::string _name;
     std::vector<sink_ptr> _sinks;
     formatter_ptr _formatter;

include/spdlog/tweakme.h

@@ -135,8 +135,8 @@
 
 
 ///////////////////////////////////////////////////////////////////////////////
-// Uncomment to enable message counting feature. Adds %i logger pattern that
-// prints log message sequence id.
+// Uncomment to enable message counting feature.
+// Use the %i in the logger pattern to display log message sequence id.
 //
 // #define SPDLOG_ENABLE_MESSAGE_COUNTER
 ///////////////////////////////////////////////////////////////////////////////