Question

I’m trying to write a program which calls a library function (http://www.diku.dk/hjemmesider/ansatte/pisinger/3dbpp.c) that solves a bin packing problem. I haven’t done any C since college and I’m pretty rusty.

I’ve got the library compiled. And statically linked so I don’t get errors about the function not existing, but now I’m getting a segfualt on the binpack3d() function, according to gdb. I think its some kind of pointer error. Here is the code that references the library function :

#include <stdio.h>
#include "3dbin.h"

int main(void)
{


int w[2];
int h[2];
int d[2];

w[0]=5;
h[0]=6;
d[0]=7;

w[1]=5;
h[1]=6;
d[1]=7;


int x[2];
int y[2];
int z[2];
int bno[1];
int lb;
int ub;

binpack3d(1, 12, 12, 24,
          w, h, d,
         x, y, z, bno,
         lb, ub, 10);


return(1);

}

Here is the function definition:

void binpack3d(int n, int W, int H, int D,
               int *w, int *h, int *d, 
               int *x, int *y, int *z, int *bno,
               int *lb, int *ub, int timelimit)
{

//code

And the header file (not sure if i did this right either)

void binpack3d(int , int , int , int ,
               int *, int *, int *, 
               int *, int *, int *, int *,
               int , int , int );

And Here is the documentation for it

 * This file contains the callable routine binpack3d with prototype
 *
 *   void binpack3d(int n, int W, int H, int D,
 *          int *w, int *h, int *d, 
 *          int *x, int *y, int *z, int *bno,
 *          int *lb, int *ub, int timelimit);
 *
 * the meaning of the parameters is the following:
 *   n         Size of problem, i.e. number of boxes to be packed.
 *             This value must be smaller than MAXITEMS defined below.
 *   W,H,D     Width, height and depth of every bin.
 *   w,h,d     Integer arrays of length n, where w[j], h[j], d[j]
 *             are the dimensions of box j for j=0,..,n-1.
 *   x,y,z,bno Integer arrays of length n where the solution found
 *             is returned. For each box j=0,..,n-1, the bin number
 *             it is packed into is given by bno[j], and x[j], y[j], z[j] 
 *             are the coordinates of it lower-left-backward corner.
 *   lb        Lower bound on the solution value (returned by the procedure).
 *   ub        Objective value of the solution found, i.e. number of bins
 *             used to pack the n boxes. (returned by the procedure).
 *   timelimit Time limit for solving the problem expressed in seconds.
 *             If set to zero, the algorithm will run until an optimal
 *             solution is found; otherwise it terminates after timelimit
 *             seconds with a heuristic solution. 

What am I doing wrong? How would I call this function and display the results.

Answer 1

It looks like your call should be the following. The original code was passing just the integer rather than the address (those two are values that are returned by the library function).

binpack3d(1, 12, 12, 24,
          w, h, d,
         x, y, z, bno,
         &lb, &ub, 10);

And the prototype needs to change to reflect that those two “return values” are int*:

void binpack3d(int , int , int , int ,
               int *, int *, int *, 
               int *, int *, int *, int *,
               int *, int *, int );