fix compiler issues with C++17 (#5)

* fix compiler issues with C++17

* fix issues with LogMsg

* next issue

* maybe this will work

src/mnxvalidate.cpp

@@ -85,7 +85,12 @@ std::string getTimeStamp(const std::string& fmt)
 #ifdef _WIN32
     localtime_s(&localTime, &time_t_now); // Windows
 #else
-    localtime_r(&time_t_now, &localTime); // Linux/Unix
+    std::tm* tmPtr = localtime(&time_t_now); // POSIX: localtime is thread-safe per thread
+    if (tmPtr) {
+        localTime = *tmPtr;
+    } else {
+        return {}; // Handle failure gracefully
+    }
 #endif
     std::ostringstream timestamp;
     timestamp << std::put_time(&localTime, fmt.c_str());

src/mnxvalidate.h

@@ -75,9 +75,32 @@ using arg_string = std::string;
 #endif
 
 using Buffer = std::vector<char>;
-using LogMsg = std::stringstream;
 using json = nlohmann::json;
 
+/// @class LogMsg
+/// @brief Stringstream class that allows rvalues to be streamed to logMessage
+class LogMsg {
+private:
+    std::stringstream stream;
+
+public:
+    LogMsg() = default;
+    LogMsg(const LogMsg& other) : stream(other.stream.str()) {} // Copy constructor
+    LogMsg(LogMsg&& other) noexcept : stream(std::move(other.stream)) {} // Move constructor
+
+    // Allow retrieval of the internal stream content
+    std::string str() const { return stream.str(); }
+
+    void flush() { stream.flush(); }
+
+    // Override operator<< to ensure LogMsg&& is always returned
+    template <typename T>
+    LogMsg&& operator<<(const T& value) {
+        stream << value;
+        return std::move(*this);
+    }
+};
+
 /// @brief defines log message severity
 enum class LogSeverity
 {

tests/mnxvalidatetests.cpp

@@ -66,7 +66,7 @@ void checkStderr(const std::vector<std::string>& expectedMessages, std::function
                 << "Message \"" << expectedMessage << "\" not found. Actual: " << capturedErrors;
         }
     }
-};
+}
 
 void checkStdout(const std::vector<std::string>& expectedMessages, std::function<void()> callback)
 {