发送列表作为参数时验证 Python 引用计数

Question

我有一个 C++ class 将 Python 模块作为文件导入，并在返回接收到的数据之前连续调用一个函数：

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();
}

虽然程序可以很好地接收数据，但当运行在不同条件下时，我在内存泄漏和崩溃方面遇到不一致。虽然我无法提供堆栈跟踪，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，当我注释掉 free_intensities_list 调用时，程序只有运行s。

提前致谢。

Answer 1

在您的 free_intensities_list 函数中，您可能正在执行双重释放。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，您可以use MALLOC_CHECK检查双重释放。

发送列表作为参数时验证 Python 引用计数

Verifying Python reference count when sending list as parameter

python

c++

cpython