no exceptions while logging

README.md

@@ -10,7 +10,6 @@ Just copy the source [folder](https://github.com/gabime/spdlog/tree/master/inclu
  * Linux (gcc 4.8.1+, clang 3.5+)
  * Windows (visual studio 2013+, cygwin/mingw with g++ 4.9.1+)
  * Mac OSX (clang 3.5+)
- * FreeBSD (gcc 4.8.1+)
 
 ##Features
 * Very fast - performance is the primary goal (see [benchmarks](#benchmarks) below).
@@ -58,22 +57,36 @@ Time needed to log 1,000,000 lines in asynchronous mode, i.e. the time it takes
 
 ## Usage Example
 ```c++
-#include <iostream>
+//
+// Copyright(c) 2015 Gabi Melman.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+//
+//
+// spdlog usage example
+//
 #include "spdlog/spdlog.h"
 
-int main(int, char* [])
+#include <iostream>
+#include <memory>
+
+void async_example();
+void syslog_example();
+void user_defined_example();
+void err_handler_example();
+
+namespace spd = spdlog;
+int main(int, char*[])
 {
-    namespace spd = spdlog;
     try
     {
-        // console logger (multithreaded and with color)
+        // Multithreaded color console
         auto console = spd::stdout_logger_mt("console", true);
-        console->info("Welcome to spdlog!") ;
+        console->info("Welcome to spdlog!");
-        console->info("An info message example {}..", 1);        
+        console->error("An info message example {}..", 1);
 
-        //Formatting examples
+        // Formatting examples
-        console->info("Easy padding in numbers like {:08d}", 12);
+        console->warn("Easy padding in numbers like {:08d}", 12);
-        console->info("Support for int: {0:d};  hex: {0:x};  oct: {0:o}; bin: {0:b}", 42);
+        console->critical("Support for int: {0:d};  hex: {0:x};  oct: {0:o}; bin: {0:b}", 42);
         console->info("Support for floats {:03.2f}", 1.23456);
         console->info("Positional args are {1} {0}..", "too", "supported");
 
@@ -81,72 +94,110 @@ int main(int, char* [])
         console->info("{:>30}", "right aligned");
         console->info("{:^30}", "centered");
 
-        //
+        spd::get("console")->info("loggers can be retrieved from a global registry using the spdlog::get(logger_name) function");
+
         // Runtime log levels
-        //
         spd::set_level(spd::level::info); //Set global log level to info
         console->debug("This message shold not be displayed!");
         console->set_level(spd::level::debug); // Set specific logger's log level
-        console->debug("Now it should..");
+        console->debug("This message shold be displayed..");
-        
+
-        //
+        // Create basic file logger (not rotated)
-        // Create a basic multithreaded file logger (or "basic_logger_st" for single threaded logger)
-        //
         auto my_logger = spd::basic_logger_mt("basic_logger", "logs/basic.txt");
         my_logger->info("Some log message");
 
-        //
+
         // Create a file rotating logger with 5mb size max and 3 rotated files
-        //
         auto rotating_logger = spd::rotating_logger_mt("some_logger_name", "logs/mylogfile", 1048576 * 5, 3);
-        for(int i = 0; i < 10; ++i)
+        for (int i = 0; i < 10; ++i)
-		      rotating_logger->info("{} * {} equals {:>10}", i, i, i*i);
+            rotating_logger->info("{} * {} equals {:>10}", i, i, i*i);
 
-        //
+        // Create a daily logger - a new file is created every day on 2:30am
-        // Create a daily logger - a new file is created every day at 2:30am
-        //
         auto daily_logger = spd::daily_logger_mt("daily_logger", "logs/daily", 2, 30);
+        daily_logger->info(123.44);
 
-        //
         // Customize msg format for all messages
-        //
         spd::set_pattern("*** [%H:%M:%S %z] [thread %t] %v ***");
         rotating_logger->info("This is another message with custom format");
 
-        spd::get("console")->info("loggers can be retrieved from a global registry using the spdlog::get(logger_name) function");
-
-        //
         // Compile time debug or trace macros.
         // Enabled #ifdef SPDLOG_DEBUG_ON or #ifdef SPDLOG_TRACE_ON
-        //
         SPDLOG_TRACE(console, "Enabled only #ifdef SPDLOG_TRACE_ON..{} ,{}", 1, 3.23);
         SPDLOG_DEBUG(console, "Enabled only #ifdef SPDLOG_DEBUG_ON.. {} ,{}", 1, 3.23);
-
+		
-        //
         // Asynchronous logging is very fast..
         // Just call spdlog::set_async_mode(q_size) and all created loggers from now on will be asynchronous..
-        //
+        async_example();
-        size_t q_size = 8192; //queue size must be power of 2
-        spdlog::set_async_mode(q_size);
-        auto async_file= spd::daily_logger_st("async_file_logger", "logs/async_log.txt");
-        async_file->info("This is async log..Should be very fast!");
 
-        //
+        // syslog example. linux/osx only..
-        // syslog example. linux only..
+        syslog_example();
-        //
+
-        #ifdef __linux__
+        // log user-defined types example..
-        std::string ident = "spdlog-example";
+        user_defined_example();
-        auto syslog_logger = spd::syslog_logger("syslog", ident, LOG_PID);
+
-        syslog_logger->warn("This is warning that will end up in syslog. This is Linux only!");
+		// Change default log error handler
-        #endif
+		err_handler_example();
-                
+
+		console->info("End of example. bye..");
+
+        // Release and close all loggers
+        spdlog::drop_all();
     }
+	// Exceptions will only be thrown upon failed logger or sink construction (not during logging)
     catch (const spd::spdlog_ex& ex)
     {
-        std::cout << "Log failed: " << ex.what() << std::endl;
+        std::cout << "Log init failed: " << ex.what() << std::endl;
-    }
+        return 1;
+    }    
 }
 
+void async_example()
+{
+    size_t q_size = 4096; //queue size must be power of 2
+    spdlog::set_async_mode(q_size);
+    auto async_file = spd::daily_logger_st("async_file_logger", "logs/async_log.txt");
+    for (int i = 0; i < 100; ++i)
+        async_file->info("Async message #{}{}", i);
+}
+
+//syslog example (linux/osx only)
+void syslog_example()
+{
+#if defined (__linux__) || defined(__APPLE__)
+    std::string ident = "spdlog-example";
+    auto syslog_logger = spd::syslog_logger("syslog", ident, LOG_PID);
+    syslog_logger->warn("This is warning that will end up in syslog. This is Linux only!");
+#endif
+}
+
+// user defined types logging by implementing operator<<
+struct my_type
+{
+    int i;
+    template<typename OStream>
+    friend OStream& operator<<(OStream& os, const my_type &c)
+    {
+        return os << "[my_type i="<<c.i << "]";
+    }
+};
+
+#include <spdlog/fmt/ostr.h> // must be included
+void user_defined_example()
+{
+    spd::get("console")->info("user defined type: {}", my_type { 14 });
+}
+
+//
+//custom error handler
+//
+void err_handler_example()
+{	
+	//can be set globaly or per logger (logger->set_error_handler(..))
+	spdlog::set_error_handler([](const std::string& msg) {
+		std::cerr << "my err handler: " << msg << std::endl;
+	});
+	spd::get("console")->info("some invalid message to trigger an error {}{}{}{}", 3);
+}
 
 ```
 

example/example.cpp

@@ -7,13 +7,13 @@
 //
 #include "spdlog/spdlog.h"
 
-#include <cstdlib> // EXIT_FAILURE
 #include <iostream>
 #include <memory>
 
 void async_example();
 void syslog_example();
 void user_defined_example();
+void err_handler_example();
 
 namespace spd = spdlog;
 int main(int, char*[])
@@ -61,12 +61,11 @@ int main(int, char*[])
         spd::set_pattern("*** [%H:%M:%S %z] [thread %t] %v ***");
         rotating_logger->info("This is another message with custom format");
 
-
         // Compile time debug or trace macros.
         // Enabled #ifdef SPDLOG_DEBUG_ON or #ifdef SPDLOG_TRACE_ON
         SPDLOG_TRACE(console, "Enabled only #ifdef SPDLOG_TRACE_ON..{} ,{}", 1, 3.23);
         SPDLOG_DEBUG(console, "Enabled only #ifdef SPDLOG_DEBUG_ON.. {} ,{}", 1, 3.23);
-
+		
         // Asynchronous logging is very fast..
         // Just call spdlog::set_async_mode(q_size) and all created loggers from now on will be asynchronous..
         async_example();
@@ -77,27 +76,29 @@ int main(int, char*[])
         // log user-defined types example..
         user_defined_example();
 
+		// Change default log error handler
+		err_handler_example();
+
+		console->info("End of example. bye..");
 
         // Release and close all loggers
         spdlog::drop_all();
     }
-
+	// Exceptions will only be thrown upon failed logger or sink construction (not during logging)
     catch (const spd::spdlog_ex& ex)
     {
-        std::cout << "Log failed: " << ex.what() << std::endl;
+        std::cout << "Log init failed: " << ex.what() << std::endl;
-        return EXIT_FAILURE;
+        return 1;
-    }
+    }    
-    return EXIT_SUCCESS;
 }
 
-
 void async_example()
 {
     size_t q_size = 4096; //queue size must be power of 2
     spdlog::set_async_mode(q_size);
     auto async_file = spd::daily_logger_st("async_file_logger", "logs/async_log.txt");
     for (int i = 0; i < 100; ++i)
-        async_file->info("Async message #{}", i);
+        async_file->info("Async message #{}{}", i);
 }
 
 //syslog example (linux/osx only)
@@ -127,3 +128,15 @@ void user_defined_example()
     spd::get("console")->info("user defined type: {}", my_type { 14 });
 }
 
+//
+//custom error handler
+//
+void err_handler_example()
+{	
+	//can be set globaly or per logger(logger->set_error_handler(..))
+	spdlog::set_error_handler([](const std::string& msg) {
+		std::cerr << "my err handler: " << msg << std::endl;
+	});
+	spd::get("console")->info("some invalid message to trigger an error {}{}{}{}", 3);
+}
+

include/spdlog/common.h

@@ -11,6 +11,8 @@
 #include <memory>
 #include <atomic>
 #include <exception>
+#include<functional>
+
 #if defined(_WIN32) && defined(SPDLOG_WCHAR_FILENAMES)
 #include <codecvt>
 #include <locale>
@@ -58,6 +60,7 @@ using level_t = details::null_atomic_int;
 using level_t = std::atomic_int;
 #endif
 
+using log_err_handler = std::function<void(const std::string &err_msg)>;
 
 //Log level enum
 namespace level

include/spdlog/details/async_log_helper.h

@@ -120,6 +120,7 @@ public:
     async_log_helper(formatter_ptr formatter,
                      const std::vector<sink_ptr>& sinks,
                      size_t queue_size,
+					 const log_err_handler err_handler,
                      const async_overflow_policy overflow_policy = async_overflow_policy::block_retry,
                      const std::function<void()>& worker_warmup_cb = nullptr,
                      const std::chrono::milliseconds& flush_interval_ms = std::chrono::milliseconds::zero(),
@@ -142,14 +143,13 @@ private:
     // queue of messages to log
     q_type _q;
 
+	log_err_handler _err_handler;
+
     bool _flush_requested;
 
     bool _terminate_requested;
 
-
+    
-    // last exception thrown from the worker thread
-    std::shared_ptr<spdlog_ex> _last_workerthread_ex;
-
     // overflow policy
     const async_overflow_policy _overflow_policy;
 
@@ -166,10 +166,7 @@ private:
     std::thread _worker_thread;
 
     void push_msg(async_msg&& new_msg);
-
+    
-    // throw last worker thread exception or if worker thread is not active
-    void throw_if_bad_worker();
-
     // worker thread main loop
     void worker_loop();
 
@@ -181,7 +178,7 @@ private:
 
     // sleep,yield or return immediatly using the time passed since last message as a hint
     static void sleep_or_yield(const spdlog::log_clock::time_point& now, const log_clock::time_point& last_op_time);
-
+		
 };
 }
 }
@@ -193,6 +190,7 @@ inline spdlog::details::async_log_helper::async_log_helper(
     formatter_ptr formatter,
     const std::vector<sink_ptr>& sinks,
     size_t queue_size,
+	log_err_handler err_handler,
     const async_overflow_policy overflow_policy,
     const std::function<void()>& worker_warmup_cb,
     const std::chrono::milliseconds& flush_interval_ms,
@@ -200,6 +198,7 @@ inline spdlog::details::async_log_helper::async_log_helper(
     _formatter(formatter),
     _sinks(sinks),
     _q(queue_size),
+	_err_handler(err_handler),
     _flush_requested(false),
     _terminate_requested(false),
     _overflow_policy(overflow_policy),
@@ -232,8 +231,7 @@ inline void spdlog::details::async_log_helper::log(const details::log_msg& msg)
 }
 
 inline void spdlog::details::async_log_helper::push_msg(details::async_log_helper::async_msg&& new_msg)
-{
+{    
-    throw_if_bad_worker();
     if (!_q.enqueue(std::move(new_msg)) && _overflow_policy != async_overflow_policy::discard_log_msg)
     {
         auto last_op_time = details::os::now();
@@ -263,14 +261,12 @@ inline void spdlog::details::async_log_helper::worker_loop()
         while(process_next_msg(last_pop, last_flush));
         if (_worker_teardown_cb) _worker_teardown_cb();
     }
-    catch (const std::exception& ex)
+	catch (const std::exception &ex) {
-    {
+		_err_handler(ex.what());
-        _last_workerthread_ex = std::make_shared<spdlog_ex>(std::string("async_logger worker thread exception: ") + ex.what());
+	}
-    }
+	catch (...) {
-    catch (...)
+		_err_handler("Unknown exception");
-    {
+	}
-        _last_workerthread_ex = std::make_shared<spdlog_ex>("async_logger worker thread exception");
-    }
 }
 
 // process next message in the queue
@@ -362,15 +358,6 @@ inline void spdlog::details::async_log_helper::sleep_or_yield(const spdlog::log_
     return sleep_for(milliseconds(200));
 }
 
-// throw if the worker thread threw an exception or not active
-inline void spdlog::details::async_log_helper::throw_if_bad_worker()
-{
-    if (_last_workerthread_ex)
-    {
-        auto ex = std::move(_last_workerthread_ex);
-        throw *ex;
-    }
-}
 
 
 

include/spdlog/details/async_logger_impl.h

@@ -26,7 +26,7 @@ inline spdlog::async_logger::async_logger(const std::string& logger_name,
         const std::chrono::milliseconds& flush_interval_ms,
         const std::function<void()>& worker_teardown_cb) :
     logger(logger_name, begin, end),
-    _async_log_helper(new details::async_log_helper(_formatter, _sinks, queue_size, overflow_policy, worker_warmup_cb, flush_interval_ms, worker_teardown_cb))
+    _async_log_helper(new details::async_log_helper(_formatter, _sinks, queue_size, _err_handler, overflow_policy, worker_warmup_cb, flush_interval_ms, worker_teardown_cb))
 {
 }
 
@@ -73,5 +73,14 @@ inline void spdlog::async_logger::_set_pattern(const std::string& pattern)
 
 inline void spdlog::async_logger::_sink_it(details::log_msg& msg)
 {
-    _async_log_helper->log(msg);
+	try 
+	{
+		_async_log_helper->log(msg);
+	}
+	catch (const std::exception &ex) {
+		_err_handler(ex.what());
+	}
+	catch (...) {
+		_err_handler("Unknown exception");
+	}
 }

include/spdlog/details/logger_impl.h

@@ -6,35 +6,39 @@
 #pragma once
 
 #include <spdlog/logger.h>
+#include <spdlog/sinks/stdout_sinks.h>
 
 #include <memory>
 #include <string>
 
+
 // create logger with given name, sinks and the default pattern formatter
 // all other ctors will call this one
 template<class It>
-inline spdlog::logger::logger(const std::string& logger_name, const It& begin, const It& end) :
+inline spdlog::logger::logger(const std::string& logger_name, const It& begin, const It& end):
-    _name(logger_name),
+	_name(logger_name),
-    _sinks(begin, end),
+	_sinks(begin, end),
-    _formatter(std::make_shared<pattern_formatter>("%+"))
+	_formatter(std::make_shared<pattern_formatter>("%+"))
-{
+{	
-
+	_level = level::info; 
-    // no support under vs2013 for member initialization for std::atomic
+	_flush_level = level::off;	
-    _level = level::info;
+	_last_err_time = 0;
-    _flush_level = level::off;
+	_err_handler = [this](const std::string &msg) { this->_default_err_handler(msg);};
 }
 
 // ctor with sinks as init list
-inline spdlog::logger::logger(const std::string& logger_name, sinks_init_list sinks_list) :
+inline spdlog::logger::logger(const std::string& logger_name, sinks_init_list sinks_list):
-    logger(logger_name, sinks_list.begin(), sinks_list.end()) {}
+	logger(logger_name, sinks_list.begin(), sinks_list.end())
+{}
 
 
 // ctor with single sink
-inline spdlog::logger::logger(const std::string& logger_name, spdlog::sink_ptr single_sink) :
+inline spdlog::logger::logger(const std::string& logger_name, spdlog::sink_ptr single_sink):
-    logger(logger_name,
+	logger(logger_name,
-{
+	{
-    single_sink
+		single_sink
-}) {}
+	})
+{}
 
 
 inline spdlog::logger::~logger() = default;
@@ -42,131 +46,143 @@ inline spdlog::logger::~logger() = default;
 
 inline void spdlog::logger::set_formatter(spdlog::formatter_ptr msg_formatter)
 {
-    _set_formatter(msg_formatter);
+	_set_formatter(msg_formatter);
 }
 
 inline void spdlog::logger::set_pattern(const std::string& pattern)
 {
-    _set_pattern(pattern);
+	_set_pattern(pattern);
 }
 
 
 template <typename... Args>
 inline void spdlog::logger::log(level::level_enum lvl, const char* fmt, const Args&... args)
 {
-    if (!should_log(lvl)) return;
+	if (!should_log(lvl)) return;
-
-    details::log_msg log_msg(&_name, lvl);
-    try
-    {
-        log_msg.raw.write(fmt, args...);
-    }
-    catch (fmt::FormatError &ex)
-    {
-        throw spdlog::spdlog_ex(std::string("format error in \"") + fmt + "\": " + ex.what());
-    }
-
-    _sink_it(log_msg);
 
+	try {
+		details::log_msg log_msg(&_name, lvl);
+		log_msg.raw.write(fmt, args...);
+		_sink_it(log_msg);
+	}
+	catch (const std::exception &ex) {
+		_err_handler(ex.what());
+	}
+	catch (...) {
+		_err_handler("Unknown exception");
+	}
 }
 
 template <typename... Args>
 inline void spdlog::logger::log(level::level_enum lvl, const char* msg)
 {
-    if (!should_log(lvl)) return;
+	if (!should_log(lvl)) return;
-
+	try {
-    details::log_msg log_msg(&_name, lvl);
+		details::log_msg log_msg(&_name, lvl);
-    log_msg.raw << msg;
+		log_msg.raw << msg;
-    _sink_it(log_msg);
+		_sink_it(log_msg);
+	}
+	catch (const std::exception &ex) {
+		_err_handler(ex.what());
+	}
+	catch (...) {
+		_err_handler("Unknown exception");
+	}
 
 }
 
 template<typename T>
 inline void spdlog::logger::log(level::level_enum lvl, const T& msg)
 {
-    if (!should_log(lvl)) return;
+	if (!should_log(lvl)) return;
-
+	try {
-    details::log_msg log_msg(&_name, lvl);
+		details::log_msg log_msg(&_name, lvl);
-    log_msg.raw << msg;
+		log_msg.raw << msg;
-    _sink_it(log_msg);
+		_sink_it(log_msg);
-
+	}
+	catch (const std::exception &ex) {
+		_err_handler(ex.what());
+	}
+	catch (...) {
+		_err_handler("Unknown exception");
+	}
 }
 
 
 template <typename... Args>
 inline void spdlog::logger::trace(const char* fmt, const Args&... args)
 {
-    log(level::trace, fmt, args...);
+	log(level::trace, fmt, args...);
 }
 
 template <typename... Args>
 inline void spdlog::logger::debug(const char* fmt, const Args&... args)
 {
-    log(level::debug, fmt, args...);
+	log(level::debug, fmt, args...);
 }
 
 template <typename... Args>
 inline void spdlog::logger::info(const char* fmt, const Args&... args)
 {
-    log(level::info, fmt, args...);
+	log(level::info, fmt, args...);
 }
 
 
 template <typename... Args>
 inline void spdlog::logger::warn(const char* fmt, const Args&... args)
 {
-    log(level::warn, fmt, args...);
+	log(level::warn, fmt, args...);
 }
 
 template <typename... Args>
 inline void spdlog::logger::error(const char* fmt, const Args&... args)
 {
-    log(level::err, fmt, args...);
+	log(level::err, fmt, args...);
 }
 
 template <typename... Args>
 inline void spdlog::logger::critical(const char* fmt, const Args&... args)
 {
-    log(level::critical, fmt, args...);
+	log(level::critical, fmt, args...);
 }
 
 
 template<typename T>
 inline void spdlog::logger::trace(const T& msg)
 {
-    log(level::trace, msg);
+	log(level::trace, msg);
 }
 
 template<typename T>
 inline void spdlog::logger::debug(const T& msg)
 {
-    log(level::debug, msg);
+	log(level::debug, msg);
 }
 
 
 template<typename T>
 inline void spdlog::logger::info(const T& msg)
 {
-    log(level::info, msg);
+	log(level::info, msg);
 }
 
 
 template<typename T>
 inline void spdlog::logger::warn(const T& msg)
 {
-    log(level::warn, msg);
+	log(level::warn, msg);
 }
 
 template<typename T>
 inline void spdlog::logger::error(const T& msg)
 {
-    log(level::err, msg);
+	log(level::err, msg);
 }
 
 template<typename T>
 inline void spdlog::logger::critical(const T& msg)
 {
-    log(level::critical, msg);
+	log(level::critical, msg);
 }
 
 
@@ -177,27 +193,38 @@ inline void spdlog::logger::critical(const T& msg)
 //
 inline const std::string& spdlog::logger::name() const
 {
-    return _name;
+	return _name;
 }
 
 inline void spdlog::logger::set_level(spdlog::level::level_enum log_level)
 {
-    _level.store(log_level);
+	_level.store(log_level);
 }
 
+inline void spdlog::logger::set_error_handler(spdlog::log_err_handler err_handler)
+{
+	_err_handler = err_handler;
+}
+
+inline spdlog::log_err_handler spdlog::logger::error_handler()
+{
+	return _err_handler;
+}
+
+
 inline void spdlog::logger::flush_on(level::level_enum log_level)
 {
-    _flush_level.store(log_level);
+	_flush_level.store(log_level);
 }
 
 inline spdlog::level::level_enum spdlog::logger::level() const
 {
-    return static_cast<spdlog::level::level_enum>(_level.load(std::memory_order_relaxed));
+	return static_cast<spdlog::level::level_enum>(_level.load(std::memory_order_relaxed));
 }
 
 inline bool spdlog::logger::should_log(spdlog::level::level_enum msg_level) const
 {
-    return msg_level >= _level.load(std::memory_order_relaxed);
+	return msg_level >= _level.load(std::memory_order_relaxed);
 }
 
 //
@@ -205,26 +232,41 @@ inline bool spdlog::logger::should_log(spdlog::level::level_enum msg_level) cons
 //
 inline void spdlog::logger::_sink_it(details::log_msg& msg)
 {
-    _formatter->format(msg);
-    for (auto &sink : _sinks)
-        sink->log(msg);
 
-    const auto flush_level = _flush_level.load(std::memory_order_relaxed);
+	_formatter->format(msg);
-    if (msg.level >= flush_level)
+	for (auto &sink : _sinks)
-        flush();
+		sink->log(msg);
+
+	const auto flush_level = _flush_level.load(std::memory_order_relaxed);
+	if (msg.level >= flush_level)
+		flush();
 }
 
 inline void spdlog::logger::_set_pattern(const std::string& pattern)
 {
-    _formatter = std::make_shared<pattern_formatter>(pattern);
+	_formatter = std::make_shared<pattern_formatter>(pattern);
 }
 inline void spdlog::logger::_set_formatter(formatter_ptr msg_formatter)
 {
-    _formatter = msg_formatter;
+	_formatter = msg_formatter;
 }
 
 inline void spdlog::logger::flush()
 {
-    for (auto& sink : _sinks)
+	for (auto& sink : _sinks)
-        sink->flush();
+		sink->flush();
+}
+
+inline void spdlog::logger::_default_err_handler(const std::string &msg)
+{
+	auto now = time(nullptr);
+	if (now - _last_err_time < 60)
+		return;
+	auto tm_time = details::os::localtime(now);
+	char date_buf[100];
+	std::strftime(date_buf, sizeof(date_buf), "%Y-%m-%d %H:%M:%S", &tm_time);
+	details::log_msg  err_msg;
+	err_msg.formatted.write("[*** LOG ERROR ***] [{}] [{}] [{}]{}", name(), msg, date_buf, details::os::eol);
+	sinks::stderr_sink_mt::instance()->log(err_msg);
+	_last_err_time = now;
 }

include/spdlog/details/registry.h

@@ -60,7 +60,12 @@ public:
         if (_formatter)
             new_logger->set_formatter(_formatter);
 
+		if (_err_handler)
+			new_logger->set_error_handler(_err_handler);
+
         new_logger->set_level(_level);
+
+
         //Add to registry
         _loggers[logger_name] = new_logger;
         return new_logger;
@@ -112,6 +117,13 @@ public:
         _level = log_level;
     }
 
+	void set_error_handler(log_err_handler handler)
+	{
+		for (auto& l : _loggers)
+			l.second->set_error_handler(handler);
+		_err_handler = handler;
+	}
+
     void set_async_mode(size_t q_size, const async_overflow_policy overflow_policy, const std::function<void()>& worker_warmup_cb, const std::chrono::milliseconds& flush_interval_ms, const std::function<void()>& worker_teardown_cb)
     {
         std::lock_guard<Mutex> lock(_mutex);
@@ -149,6 +161,7 @@ private:
     std::unordered_map <std::string, std::shared_ptr<logger>> _loggers;
     formatter_ptr _formatter;
     level::level_enum _level = level::info;
+	log_err_handler _err_handler;
     bool _async_mode = false;
     size_t _async_q_size = 0;
     async_overflow_policy _overflow_policy = async_overflow_policy::block_retry;

include/spdlog/details/spdlog_impl.h

@@ -147,6 +147,13 @@ inline void spdlog::set_level(level::level_enum log_level)
     return details::registry::instance().set_level(log_level);
 }
 
+inline void spdlog::set_error_handler(log_err_handler handler)
+{
+	return details::registry::instance().set_error_handler(handler);
+}
+
+
+
 
 inline void spdlog::set_async_mode(size_t queue_size, const async_overflow_policy overflow_policy, const std::function<void()>& worker_warmup_cb, const std::chrono::milliseconds& flush_interval_ms, const std::function<void()>& worker_teardown_cb)
 {

include/spdlog/logger.h

@@ -19,7 +19,6 @@
 #include <memory>
 #include <string>
 
-
 namespace spdlog
 {
 
@@ -52,14 +51,17 @@ public:
     template <typename T> void warn(const T&);
     template <typename T> void error(const T&);
     template <typename T> void critical(const T&);
-
+	
-
     bool should_log(level::level_enum) const;
     void set_level(level::level_enum);
     level::level_enum level() const;
     const std::string& name() const;
     void set_pattern(const std::string&);
-    void set_formatter(formatter_ptr);
+    void set_formatter(formatter_ptr);	
+
+	// error handler
+	void set_error_handler(log_err_handler);
+	log_err_handler error_handler();
 
     // automatically call flush() if message level >= log_level
     void flush_on(level::level_enum log_level);
@@ -70,11 +72,16 @@ protected:
     virtual void _set_pattern(const std::string&);
     virtual void _set_formatter(formatter_ptr);
 
+	// default error handler: print the error to stderr with the max rate of 1 message/minute
+	virtual void _default_err_handler(const std::string &msg);
+	
     const std::string _name;
     std::vector<sink_ptr> _sinks;
     formatter_ptr _formatter;
     spdlog::level_t _level;
     spdlog::level_t _flush_level;
+	log_err_handler _err_handler;	
+	std::atomic<time_t> _last_err_time;
 };
 }
 

include/spdlog/spdlog.h

@@ -41,6 +41,11 @@ void set_formatter(formatter_ptr f);
 //
 void set_level(level::level_enum log_level);
 
+//
+// Set global error handler
+//
+void set_error_handler(log_err_handler);
+
 //
 // Turn on async mode (off by default) and set the queue size for each async_logger.
 // effective only for loggers created after this call.

tests/errors.cpp

@@ -0,0 +1,61 @@
+/*
+* This content is released under the MIT License as specified in https://raw.githubusercontent.com/gabime/spdlog/master/LICENSE
+*/
+#include "includes.h"
+
+#include<iostream>
+
+
+TEST_CASE("default_error_handler", "[errors]]")
+{
+	prepare_logdir();
+	std::string filename = "logs/simple_log.txt";
+
+	auto logger = spdlog::create<spdlog::sinks::simple_file_sink_mt>("logger", filename, true);
+	logger->set_pattern("%v");				
+	logger->info("Test message {} {}", 1);	
+	logger->info("Test message {}", 2);
+	logger->flush();
+
+	REQUIRE(file_contents(filename) == std::string("Test message 2\n"));
+	REQUIRE(count_lines(filename) == 1);
+}
+
+
+struct custom_ex{};
+TEST_CASE("custom_error_handler", "[errors]]")
+{
+	prepare_logdir();
+	std::string filename = "logs/simple_log.txt";	
+	auto logger = spdlog::create<spdlog::sinks::simple_file_sink_mt>("logger", filename, true);	
+	logger->set_error_handler([=](const std::string& msg) {
+		throw custom_ex();
+	});
+	logger->info("Good message #1");
+	REQUIRE_THROWS_AS(logger->info("Bad format msg {} {}", "xxx"), custom_ex);
+	logger->info("Good message #2");	
+	REQUIRE(count_lines(filename) == 2);
+}
+
+TEST_CASE("async_error_handler", "[errors]]")
+{
+	prepare_logdir();
+	std::string err_msg("log failed with some msg");
+	spdlog::set_async_mode(128);
+	std::string filename = "logs/simple_async_log.txt";
+	{
+		auto logger = spdlog::create<spdlog::sinks::simple_file_sink_mt>("logger", filename, true);
+		logger->set_error_handler([=](const std::string& msg) {
+			std::ofstream ofs("logs/custom_err.txt");
+			if (!ofs) throw std::runtime_error("Failed open logs/custom_err.txt");
+			ofs << err_msg;			
+		});		
+		logger->info("Good message #1");	
+		logger->info("Bad format msg {} {}", "xxx");
+		logger->info("Good message #2");
+		spdlog::drop("logger"); //force logger to drain the queue and shutdown
+		spdlog::set_sync_mode();
+	}
+	REQUIRE(count_lines(filename) == 2);
+	REQUIRE(file_contents("logs/custom_err.txt") == err_msg);
+}

tests/format.cpp

@@ -49,24 +49,7 @@ TEST_CASE("log_levels", "[log_levels]")
     REQUIRE(log_info("Hello", spdlog::level::trace) == "Hello");
 }
 
-TEST_CASE("invalid_format", "[format]")
+
-{
-
-    using namespace spdlog::sinks;
-    spdlog::logger null_logger("null_logger", std::make_shared<null_sink_st>());
-    REQUIRE_THROWS_AS(
-        null_logger.info("{} {}", "first"),
-        spdlog::spdlog_ex);
-
-    REQUIRE_THROWS_AS(
-        null_logger.info("{0:f}", "aads"),
-        spdlog::spdlog_ex);
-
-    REQUIRE_THROWS_AS(
-        null_logger.info("{0:kk}", 123),
-        spdlog::spdlog_ex);
-
-}
 
 
 

tests/tests.vcxproj

@@ -125,6 +125,7 @@
     </Link>
   </ItemDefinitionGroup>
   <ItemGroup>
+    <ClCompile Include="errors.cpp" />
     <ClCompile Include="file_helper.cpp" />
     <ClCompile Include="file_log.cpp" />
     <ClCompile Include="format.cpp" />

tests/tests.vcxproj.filters

@@ -33,6 +33,9 @@
     <ClCompile Include="utils.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="errors.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="includes.h">