use fold expression if C++17

libi2pd/Log.h

@@ -161,6 +161,7 @@ void LogPrint (std::stringstream& s, TValue&& arg) noexcept
 	s << std::forward<TValue>(arg);
 }
 
+#if (__cplusplus < 201703L) // below C++ 17
 /** internal usage only -- folding args array to single string */
 template<typename TValue, typename... TArgs>
 void LogPrint (std::stringstream& s, TValue&& arg, TArgs&&... args) noexcept
@@ -168,6 +169,7 @@ void LogPrint (std::stringstream& s, TValue&& arg, TArgs&&... args) noexcept
 	LogPrint (s, std::forward<TValue>(arg));
 	LogPrint (s, std::forward<TArgs>(args)...);
 }
+#endif
 
 /**
  * @brief Create log message and send it to queue
@@ -184,7 +186,11 @@ void LogPrint (LogLevel level, TArgs&&... args) noexcept
 	// fold message to single string
 	std::stringstream ss("");
 
+#if (__cplusplus >= 201703L) // C++ 17 or higher
+	(LogPrint (ss, std::forward<TArgs>(args)), ...);
+#else
 	LogPrint (ss, std::forward<TArgs>(args)...);
+#endif
 
 	auto msg = std::make_shared<i2p::log::LogMsg>(level, std::time(nullptr), ss.str());
 	msg->tid = std::this_thread::get_id();