Add the class PyObjectPtr to manage reference counting.

python/PyLogger.cxx

@@ -41,7 +41,6 @@ PyLogger::PyLogger(PyObject* logger)
 {
   if (PyObject_IsInstance(logger, FGLogger_PyClass)) {
     logger_pyclass = logger;
-    Py_INCREF(logger_pyclass);
   } else {
     PyErr_SetString(PyExc_TypeError, "The logger must be an instance of FGLogger");
   }
@@ -50,7 +49,7 @@ PyLogger::PyLogger(PyObject* logger)
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 void PyLogger::SetLevel(LogLevel level) {
-  PyObject* py_level;
+  PyObjectPtr py_level;
 
   switch (level)
   {
@@ -74,38 +73,33 @@ void PyLogger::SetLevel(LogLevel level) {
     break;
   }
 
-  bool success = CallPythonMethodWithArguments("set_level", py_level);
-  if (success) FGLogger::SetLevel(level);
-  Py_DECREF(py_level);
+  PyObjectPtr result = CallPythonMethodWithArguments("set_level", py_level);
+  if (result) FGLogger::SetLevel(level);
 }
 
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 void PyLogger::FileLocation(const std::string& filename, int line)
 {
-  PyObject* py_filename = PyUnicode_FromString(filename.c_str());
-  PyObject* py_line = PyLong_FromLong(line);
-  PyObject* args = PyTuple_Pack(2, py_filename, py_line);
+  PyObjectPtr py_filename = PyUnicode_FromString(filename.c_str());
+  PyObjectPtr py_line = PyLong_FromLong(line);
+  PyObjectPtr args = PyTuple_Pack(2, py_filename.get(), py_line.get());
   CallPythonMethodWithTuple("file_location", args);
-  Py_DECREF(args);
-  Py_DECREF(py_filename);
-  Py_DECREF(py_line);
 }
 
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 void PyLogger::Message(const std::string& message)
 {
-  PyObject* msg = PyUnicode_FromString(message.c_str());
+  PyObjectPtr msg = PyUnicode_FromString(message.c_str());
   CallPythonMethodWithArguments("message", msg);
-  Py_DECREF(msg);
 }
 
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 void PyLogger::Format(LogFormat format)
 {
-  PyObject* py_format;
+  PyObjectPtr py_format;
 
   switch (format)
   {
@@ -142,35 +136,27 @@ void PyLogger::Format(LogFormat format)
   }
 
   CallPythonMethodWithArguments("format", py_format);
-  Py_DECREF(py_format);
 }
 
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
-bool PyLogger::CallPythonMethodWithArguments(const char* method_name, PyObject* arg)
+PyObjectPtr PyLogger::CallPythonMethodWithArguments(const char* method_name, const PyObjectPtr& arg)
 {
-  PyObject* tuple = PyTuple_Pack(1, arg);
-  bool success = CallPythonMethodWithTuple(method_name, tuple);
-  Py_DECREF(tuple);
-  return success;
+  PyObjectPtr tuple = PyTuple_Pack(1, arg.get());
+  return CallPythonMethodWithTuple(method_name, tuple);
 }
 
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
-bool PyLogger::CallPythonMethodWithTuple(const char* method_name, PyObject* tuple)
+PyObjectPtr PyLogger::CallPythonMethodWithTuple(const char* method_name, const PyObjectPtr& tuple)
 {
-  PyObject* method = PyObject_GetAttrString(logger_pyclass, method_name);
+  PyObjectPtr method = PyObject_GetAttrString(logger_pyclass.get(), method_name);
   assert(method); // This should not fail as the constructor has checked the type of logger_pyclass.
 
-  PyObject* result = PyObject_CallObject(method, tuple);
-  Py_DECREF(method);
+  PyObjectPtr result = PyObject_CallObject(method.get(), tuple.get());
 
-  if (result) {
-    Py_DECREF(result);
-    return true;
-  }
+  if (!result) PyErr_Print();
 
-  PyErr_Print();
-  return false;
+  return result;
 }
 } // namespace JSBSim

python/PyLogger.h

@@ -36,22 +36,76 @@ extern PyObject* FGLogger_PyClass;
 extern PyObject* LogLevel_PyClass;
 extern PyObject* LogFormat_PyClass;
 
+// Helper class to manage the reference count of a PyObject.
+class PyObjectPtr {
+public:
+  PyObjectPtr(PyObject* obj = nullptr) noexcept
+    : object(obj) {}
+
+  // Copy constructor
+  PyObjectPtr(const PyObjectPtr& other) noexcept {
+    object = other.object;
+    Py_XINCREF(object);
+  }
+
+  // Move constructor
+  PyObjectPtr(PyObjectPtr&& other) noexcept
+    : object(other.object)
+  {
+    other.object = nullptr;
+  }
+
+  // Copy assignment operator
+  PyObjectPtr& operator=(const PyObjectPtr& other) noexcept {
+    if (this != &other) {
+      Py_XDECREF(object); // Decrement the reference count of the current object
+      object = other.object;
+      Py_XINCREF(object); // Increment the reference count of the new object
+    }
+    return *this;
+  }
+
+  PyObjectPtr& operator=(PyObject* src) noexcept {
+    Py_XDECREF(object);
+    object = src;
+    return *this;
+  }
+
+  // Move assignment operator
+  PyObjectPtr& operator=(PyObjectPtr&& other) noexcept {
+    if (this != &other) {
+      Py_XDECREF(object); // Decrement the reference count of the current object
+      object = other.object;
+      other.object = nullptr; // Prevent the source from decrementing the reference count
+    }
+    return *this;
+  }
+
+  ~PyObjectPtr() noexcept { Py_XDECREF(object); }
+
+  PyObject* get() const noexcept { return object; }
+  operator bool() const noexcept { return object != nullptr; }
+
+protected:
+  PyObject* object;
+};
+
+
 class PyLogger : public FGLogger
 {
 public:
   explicit PyLogger(PyObject* logger);
-  ~PyLogger() override { Py_XDECREF(logger_pyclass); }
   void SetLevel(LogLevel level) override;
   void FileLocation(const std::string& filename, int line) override;
   void Message(const std::string& message) override;
   void Format(LogFormat format) override;
   void Flush(void) override { CallPythonMethodWithTuple("flush", nullptr); }
 
 private:
-  bool CallPythonMethodWithTuple(const char* method_name, PyObject* tuple);
-  bool CallPythonMethodWithArguments(const char* method_name, PyObject* arg);
+  PyObjectPtr CallPythonMethodWithTuple(const char* method_name, const PyObjectPtr& tuple);
+  PyObjectPtr CallPythonMethodWithArguments(const char* method_name, const PyObjectPtr& arg);
 
-  PyObject* logger_pyclass = nullptr;
+  PyObjectPtr logger_pyclass;
 };
 }
 #endif