Python扩展模块段错误

Question

我在C写了一个漂亮的钳工，我想在python中提供一个接口。所以我为它写了一个扩展模块（见下文）。但是，当我运行时

from nelder_mead import minimize 
minimize(lambda x: x[0]**2, [42]) 

我得到一个段错误。我不知道从哪里开始调试，这个问题是否明显？当我从C调用钳工时，它工作得很好。

这里是我的包装，功能原始的调配者的顶部：

#include "Python.h" 
void _minimize(double (*func)(double* x, void* args), double* x0, int N, void* args); 

typedef struct arg_struct { 
    PyObject* func; 
    int N; 
} arg_struct; 

double func(double* x, void* args){ 
    //Build a PyList off of x 
    int N = ((arg_struct*)args)->N; 
    PyObject* x_list = PyList_New(N); 
    for (int i=0; i<N; i++){ PyList_SetItem(x_list, i, PyFloat_FromDouble(x[i])); } 

    //Pass x_list into the python objective function 
    PyObject* arglist = Py_BuildValue("(O)", x_list); 
    PyObject* result = PyObject_CallObject(((arg_struct*)args)->func, arglist); 

    //Convert result to a double and return 
    return PyFloat_AsDouble(result); 
} 

static PyObject* minimize(PyObject* self, PyObject* py_args){ 
    //Get object pointers to f and x0 
    PyObject* py_func, *x0_list; 
    if (!PyArg_ParseTuple(py_args, "OO", py_func, x0_list)) return NULL; 

    //Copy doubles out of x0_list to a regular double* array 
    int N = PyList_Size(x0_list); 
    double* x0 = (double*)malloc(N*sizeof(double)); 
    for (int i=0; i<N; i++) x0[i] = PyFloat_AsDouble(PyList_GetItem(x0_list, i)); 

    //Set up an arg_struct and minimize py_func(x0) 
    arg_struct c_args = { py_func, N }; 
    _minimize(&func, x0, N, (void*)&c_args); 

    //Now build a list off of x0 and return it 
    PyObject* result_list = PyList_New(N); 
    for (int i=0; i<N; i++){ PyList_SetItem(result_list, i, PyFloat_FromDouble(x0[i])); } 
    return result_list; 
    } 

//Initialize the module with the module table and stuff 
static PyMethodDef module_methods[] = { 
    { "minimize", minimize, METH_VARARGS, "Minimize a function." }, 
    { NULL, NULL, 0, NULL } 
}; 
PyMODINIT_FUNC 
initnelder_mead(void){ 
    (void) Py_InitModule("nelder_mead", module_methods); 
} 

这是我的setup.py：

from distutils.core import setup 
from distutils.extension import Extension 

setup(name='nelder_mead', 
     ext_modules = [Extension('nelder_mead', sources = ['wrapper.c', 'nm.c'])]) 

Answer 1

原来是两个小东西。正如@robyschek指出的那样，我应该把x[0]而不是x，这会导致类型错误。此外，事实证明，参数解析需要指针指针： 将其更改为PyArg_ParseTuple(py_args, "OO", &py_func, &x0_list)可以正常工作。