copiar matriz a otra(sin resolver)

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

void gen_matriz (int** nuevo, int matriz[20] [20]){
int j, k, y;int dup;int num_elem[20];
nuevo = (int**) calloc(20, sizeof(int*));

for (y = 0; y < 20; y++){
num_elem[y] = 0;

for (k = 0; k < 20; k++){
dup = 0;j = 0;

while ((j < 20) && !dup){
if (k != j){
dup = matriz[y][k] == matriz[y][j];
printf ("y=%i %i %i\n",y, j, dup);}
j++;}

printf ("dup %i\n", dup);

if (!dup){
num_elem[y]++;
if (nuevo[y] == NULL) nuevo[y] = (int*) malloc(sizeof (int));
else
nuevo[y] = (int*) realloc(nuevo[y], num_elem[y] * sizeof (int));
int indice = num_elem[y] - 1;
nuevo[y][indice] = matriz[y][k];
printf (" posicion %i %i : %i\n", y, k, nuevo [y] [indice]);}
                }

        }

for(y = 0; y < 20; y++)
for(k = 0; k < num_elem[y]; k++)
printf("nuevo[%i][%i] = %i\n", y, k, nuevo[y][k]);
}