*** Error in `python': munmap_chunk(): invalid pointer: 0x00007fdfb8c28950 ***

Question

i want to write a C-extension for python, as you can see below ,the aim of this code is to calculate the euclidean-dist from 2 lists of float.

the C code:

#include <python2.7/Python.h>
#include <math.h>

static PyObject* cutil_euclidean_dist(PyObject* self, PyObject* args) {
    PyObject *seq_a, *seq_b;
    int n;
    float * array_a,* array_b;
    PyObject *item;

    printf("prepare to check input");

    PyArg_ParseTuple(args,"iOO", &n , &seq_a, &seq_b);
    if (!PySequence_Check(seq_a) || !PySequence_Check(seq_b)) {
       PyErr_SetString(PyExc_TypeError, "expected sequence");
       return NULL;
    }

    array_a =(float *)malloc(sizeof(float)*n);
    array_b =(float *)malloc(sizeof(float)*n);  

    if (NULL == array_a || NULL == array_b){
        PyErr_SetString(PyExc_TypeError, "malloc failed!");
        return NULL;
    }

    printf("%d",array_a==NULL);
    printf("%d",array_b==NULL);

    printf("malloc yes ");
    printf("n=%d",n);

    int i;
    for(i=0;i<n;i++){
        printf("111");

        item = PySequence_GetItem(seq_a,i);

        printf("after get item");
        if (!PyFloat_Check(item)) {
            printf("in float check");
            free(array_a);  /* free up the memory before leaving */
            free(array_b);
            free(seq_a);
            free(seq_b);
            PyErr_SetString(PyExc_TypeError, "expected sequence of float");
            return NULL;
        }
        array_a[i] = PyFloat_AsDouble(item);

        printf("a=%f",array_a[i]);

        Py_DECREF(item);

        item = PySequence_GetItem(seq_b,i);
        if(!PyFloat_Check(item)) {
            free(array_a);
            free(array_b);
            free(seq_a);
            free(seq_b);
            PyErr_SetString(PyExc_TypeError, "expected sequence of float");  
        }
        array_b[i] = PyFloat_AsDouble(item);
        Py_DECREF(item);
    }

    printf("array analyze yes");

    double sum = 0;
    for(i=0;i<n;i++){
        double delta = array_a[i] - array_b[i];
        sum += delta * delta;
    }

    free(array_a);
    free(array_b);
    free(seq_a);
    free(seq_b);

    return Py_BuildValue("d",sqrt(sum));
}

static PyMethodDef cutil_methods[] = {
    {"c_euclidean_dist",        (PyCFunction)cutil_euclidean_dist,METH_VARARGS,NULL},
    {NULL,NULL,0,NULL}
};

PyMODINIT_FUNC initcutil(void) {
    Py_InitModule3("cutil", cutil_methods, "liurui's c extension for     python");
} 

the python code:

import cutil
cutil.c_euclidean_dist(2,[1.0,1.0],[2.0,2.0])

the result:

*** Error in `python': munmap_chunk(): invalid pointer: 0x00007fdfb8c28950 ***  (core dumped)

So i can not succeed in calling this function.

who can help me with this problem? thanks a lot

i even do not know what's wrong with it.

By the way: when i complie the code, the gcc asked me to add -fPIC , but when i add -fPIC,the says gcc can not find Python.h eventually i changed:

#include <Python.h>

into this:

#include <python2.7/Python.h>

then it is OK

WHEN i comment the two sentences, the code runs well:

free(seq_a);
free(seq_b);

but i think without the 2 sentences , there will be a memory leak because the seq_a , seq_b will not be freed

Answer 1

You can only use free() to deallocate memory which was allocated using malloc() .

seq_a and seq_b which you are incorrectly trying to free are not allocated via malloc .

Also, you should check out the PyObject and reference counting chapter in Python docs.