在将列表作为参数发送时验证Python引用计数

Question

我有一个C++类，它将Python模块作为文件导入，并在返回接收到的数据之前不断为其调用函数：

ProgramLiveProcess::ProgramLiveProcess() {
//Start Python to run the Program Python code
Py_Initialize();
//Import the Program live processing module
program_live_processing_module = PyImport_ImportModule(MODULE_NAME);
//Get the objects for the functions to call
live_process = PyObject_GetAttrString(program_live_processing_module, "Program_LiveProcess");
}
//Creates Python list from intensities array
PyObject* ProgramLiveProcess::get_intensities_list(unsigned int intensities[INTENSITIES_DATA_SIZE]) {
PyObject* tr = PyList_New(0);
for (int i = 0; i < INTENSITIES_DATA_SIZE; i++) {
PyObject* ta = PyLong_FromLong(intensities[i]);
PyList_Append(tr, ta);
}
return tr;
}
//TODO: Make this actually work
//Frees objects in intensities Python list and the list itself
void ProgramLiveProcess::free_intensities_list(PyObject* i_list) {
//std::cout << std::to_string(i_list->ob_refcnt) << std::endl;
for (int i = 0; i < INTENSITIES_DATA_SIZE; i++) {
PyObject* ta = PyList_GET_ITEM(i_list, i);
Py_DECREF(ta);
}
Py_DECREF(i_list);
}
processed_data* ProgramLiveProcess::send_to_program_live_process(unsigned int intensities[INTENSITIES_DATA_SIZE], bool use_sensor_1) {
//Call the Program_LiveProcess function
PyObject* intensities_py = get_intensities_list(intensities);
PyObject* calculate_args = PyTuple_Pack(2, intensities_py, use_sensor_1 ? Py_True : Py_False); //True or false depending on if using sensor 1 or 2
PyObject* processed_data_tuple = PyObject_CallObject(live_process, calculate_args);
Py_DECREF(calculate_args);
free_intensities_list(intensities_py);
//Get the data from the function
PyObject* s0p = PyTuple_GetItem(processed_data_tuple, 0);
PyObject* s0t = PyTuple_GetItem(processed_data_tuple, 1);
//Return a struct containing the data
processed_data* to_return = (processed_data*)malloc(PROCESSED_DATA_STRUCT_SIZE);
if (to_return == NULL)
return to_return;
to_return->sensor_1_pressure = (float)PyFloat_AS_DOUBLE(s0p);
to_return->sensor_1_temperature = (float)PyFloat_AS_DOUBLE(s0t);
//Free python objects and return
Py_DECREF(s0p);
Py_DECREF(s0t);
return to_return;
}
//Finalize the interpreter after freeing objects
ProgramLiveProcess::~ProgramLiveProcess() {
Py_DECREF(live_process);
free(live_process);
Py_Finalize();
}

虽然程序接收数据很好，但在不同条件下运行时，内存泄漏和崩溃方面存在不一致。虽然我不能给出堆栈跟踪，但我想知道我在创建或取消引用Python对象方面是否做错了什么。通常，只有当我注释掉free_intensions_list调用时，程序才会运行。

提前谢谢。

Answer 1

在free_intensities_list函数中，您可能正在执行两次释放。请考虑改用Py_XDECREF。

void Py_DECREF(PyObject *o)
Decrement the reference count for object o. The object must not be NULL; if you aren’t sure that it isn’t NULL, use Py_XDECREF(). If the reference count reaches zero, the object’s type’s deallocation function (which must not be NULL) is invoked.

来源：https://docs.python.org/3/c-api/refcounting.html

此外，您还可以使用MALLOC_CHECK来检查是否有两次释放。