Please describe the problem:
To get shuffled natural numbers sequence, I writed a cmp_func which returns [-1,
0,1] randomly and then quick sorted the array of integers. When I used qsort of 
stdlib.h , it just worked fine, but when replace it with g_qsort_with_data of 
glib.h, SOMETIMES causes SegV. 

Steps to reproduce:
#include <glib.h>
#define A 16

gint gint_cmp_shuffle(const gint *a, const gint *b, gpointer user_data)
{
  return g_random_int_range(-1, 2);
}

gint main(gint argc, gchar *argv[])
{ 
  gint i;
  gint table[A];
  for (i = 0; i < A; i++) table[i] = i;
  for (i = 0; i < 128; i++) {
    g_print("%d\n", i);
    g_qsort_with_data(table, A, sizeof(gint), (GCompareDataFunc)
gint_cmp_shuffle, NULL);
  }
  return 0;
}


Actual results:
Outputs of gprint are like "0 1 2 ... 17 Segmentation fault" "0 1 2 ... 6 
Segmentation fault".

Expected results:
"0 1 2 ... 126 127"

Does this happen every time?
Yes.

Other information:
Following codes works fine, it always outputs "0 1 2 ... 126 127" and ends 
normally.

#include <stdlib.h>
#include <glib.h>
#define A 16

int int_cmp_shuffle(const int *a, const int *b)
{
  return g_random_int_range(-1, 2);
}

int main(int argc, char *argv[])
{ 
  int i;
  int table[A];
  for (i = 0; i < A; i++) table[i] = i;
  for (i = 0; i < 128; i++) {
    g_print("%d\n", i);
    qsort(table, A, sizeof(int), (int(*)(const void*, const void*))
int_cmp_shuffle);
  }
  return 0;
}