conditional logging implementation

include/spdlog/details/logger_impl.h

@@ -146,6 +146,15 @@ inline void spdlog::logger::warn(const char* fmt, const Arg1 &arg1, const Args&.
     log(level::warn, fmt, arg1, args...);
 }
 
+template <typename Arg1, typename... Args> 
+inline void spdlog::logger::warn_if(const bool flag, const char* fmt, const Arg1& arg1, const Args&... args)
+{
+    if (flag)
+    {
+        log(level::warn, fmt, arg1, args...);
+    }
+}
+
 template <typename Arg1, typename... Args>
 inline void spdlog::logger::error(const char* fmt, const Arg1 &arg1, const Args&... args)
 {
@@ -184,6 +193,15 @@ inline void spdlog::logger::warn(const T& msg)
     log(level::warn, msg);
 }
 
+template<typename T>
+inline void spdlog::logger::warn_if(const bool flag, const T& msg)
+{
+    if (flag)
+    {
+        log(level::warn, msg);
+    }
+}
+
 template<typename T>
 inline void spdlog::logger::error(const T& msg)
 {

include/spdlog/logger.h

@@ -43,6 +43,8 @@ public:
     template <typename Arg1, typename... Args> void warn(const char* fmt, const Arg1&, const Args&... args);
     template <typename Arg1, typename... Args> void error(const char* fmt, const Arg1&, const Args&... args);
     template <typename Arg1, typename... Args> void critical(const char* fmt, const Arg1&, const Args&... args);
+
+    template <typename Arg1, typename... Args> void warn_if(const bool flag, const char* fmt, const Arg1&, const Args&... args);
 #ifdef SPDLOG_WCHAR_TO_UTF8_SUPPORT
     template <typename... Args> void log(level::level_enum lvl, const wchar_t* msg);
     template <typename... Args> void log(level::level_enum lvl, const wchar_t* fmt, const Args&... args);
@@ -62,6 +64,8 @@ public:
     template <typename T> void error(const T&);
     template <typename T> void critical(const T&);
 
+    template <typename T> void warn_if(const bool flag, const T&);
+
     bool should_log(level::level_enum) const;
     void set_level(level::level_enum);
     level::level_enum level() const;