Hi,

The vectors times and fluxes are destroyed when exiting the function start, the memory allocated and pointed to be times and fluxes are invalid upon exiting the function.

Thor Andreas


On Sun, Sep 29, 2013 at 12:53 AM, Nicholas Earl <nchlsearl@gmail.com> wrote:
I'm struggling with returning a struct value using ctypes. Mainly, it keeps segfaulting when I try and get the values from the returned object. I have my python script setup like this:

import ctypes
import numpy as np
from numpy.ctypeslib import ndpointer


class PhotoInfo(ctypes.Structure):
    _fields_ = [
        ('times', ctypes.POINTER(ctypes.c_double)),
        ('fluxes', ctypes.POINTER(ctypes.c_double)),
    ]


def main():
    lib = ctypes.cdll.LoadLibrary('cfile.so')

    start = lib.start
    start.restype = ctypes.POINTER(PhotoInfo)
    start.argtypes = [
        ctypes.c_int,
        ndpointer(ctypes.c_double),
    ]

    N = 3
    mass = np.array([0.00020335520, 5.977884E-05, 9.320397E-08])

    phin = start(N, mass)

    print phin[0].times[0]


And in my c file:

#include <iostream>
#include <iomanip>
#include <fstream>
#include <sstream>
#include <string>
#include <vector>
#include <math.h>
#include <stdlib.h>
#include <stdio.h>

using namespace std;

typedef struct {
  double *times;
  double *fluxes;
} PhotoInfo;

extern "C" {
  PhotoInfo *start(int N, double *mass);
}

PhotoInfo *start(int N, double *mass) {
  PhotoInfo phin;
  vector<double> times;
  vector<double> fluxes;

// Here, I read in a file and fill times and fluxes with doubles using
// times.push_back(t) and fluxes.push_back(f)\

  phin.times = &times[0];
  phin.fluxes = &times[0];
  return &phin;
}


Any guidance on this would be greatly appreciated!

Nicholas Earl
Graduate Research Assistant
San Diego State University

------------------------------------------------------------------------------
October Webinars: Code for Performance
Free Intel webinars can help you accelerate application performance.
Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from
the latest Intel processors and coprocessors. See abstracts and register >
http://pubads.g.doubleclick.net/gampad/clk?id=60133471&iu=/4140/ostg.clktrk
_______________________________________________
ctypes-users mailing list
ctypes-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/ctypes-users