AVL tree silently accept duplicate keys

[Domingo Alvarez Duarte]

Hello !

Replacing usages of AVL tree by SplayTree I found that AVL tree silently 
accepts duplicate keys on "avl_insert_node" see example bellow, there is 
only one way to find by key "avl_find_node" which make it prone to write 
incorrect code:

====

#include <stdio.h>
#include <stdlib.h>
#include "avl.h"

int main(int argc, char *argv[])
{
    AVL *tree = avl_create_tree(avl_strcmp, NULL);
    AVLNODE *node1 = avl_insert_node(tree, "one");
    printf("node1 = %p\n", node1);
    AVLNODE *node2 = avl_insert_node(tree, "one");
    printf("node2 = %p\n", node2);
    AVLNODE *node3 = avl_insert_node(tree, "one");
    printf("node3 = %p\n", node3);
    AVLNODE *node = avl_find_node(tree, "one");
    printf("node = %p\n", node);
    avl_delete_node(tree, node1);
    node = avl_find_node(tree, "one");
    printf("node = %p\n", node);
    avl_delete_node(tree, node2);
    node = avl_find_node(tree, "one");
    printf("node = %p\n", node);
    avl_delete_tree(tree);
    return 0;
}

====

Build:

====

gcc -g -o test-avl test-avl.c -I../src/misc -I../src ../src/.libs/libglpk.a

====

Output:

=====

./test-avl
node1 = 0x55f599e6d908
node2 = 0x55f599e6d940
node3 = 0x55f599e6d978
node = 0x55f599e6d940
node = 0x55f599e6d940
node = 0x55f599e6d978

=====

Cheers !