typedef struct s_variable {
    char *name;
    int start;
    int end;
    int reg;
    int overlaps;
    gboolean reassigned;
} variable;

gint varcmp(gconstpointer a, gconstpointer b) {
    variable *x = (variable *)a;
    variable *y = (variable *)b;
    if (x->end < y->end)
        return -1; 
    else if (x->end == y->end)
        return 0;
    return 1;
}

gboolean make_tree(gpointer key, gpointer value, gpointer data) {
    variable *var = (variable *)value;
    GTree *t = (GTree *)data;
    printf("Adding %s(end=%d) to the tree %p", var->name, var->end, t);
    g_tree_insert(t, var->name, var);
    printf(" (%d)\n", g_tree_nnodes(t));
    return TRUE;
}

GTree *t = g_tree_new(varcmp);
printf("Tree is at %p\n",t);
g_hash_table_foreach(vars, make_tree, t);
printf("Tree now has %d elements\n", g_tree_nnodes(t));

/* output:
Tree is at 0x804df70
Adding $five(end=6) to the tree 0x804df70 (1)
Adding $one(end=2) to the tree 0x804df70 (1)
Adding $two(end=3) to the tree 0x804df70 (1)
Adding $six(end=7) to the tree 0x804df70 (1)
Adding $three(end=4) to the tree 0x804df70 (1)
Adding $four(end=5) to the tree 0x804df70 (1)
Adding $seven(end=8) to the tree 0x804df70 (1)
Adding $ten(end=11) to the tree 0x804df70 (1)
Adding $zero(end=1) to the tree 0x804df70 (1)
Adding $nine(end=10) to the tree 0x804df70 (1)
Adding $eight(end=9) to the tree 0x804df70 (1)
Tree now has 1 elements
*/