Appending a ADT list seg fault - c

Question

So im trying to append a list but every time I use the append function, it just crashes (SEG FAULT). I narrowed it down to around a line that in insert value and I marked it in the code below.
so here is the structs/lists
/*Declration of the struct*/
typedef struct Element {
value_type value;
Key_type key;
struct Element * next;
struct Element * sort;
}Node;
/*ADT declration*/
typedef struct List {
Node * head;
Node * head_sort;
Node * tail;
Node * tail_sort;
int size;
}Sorted_List;
Here is the rest of the code
/*Fucntion to add values ot the end using tail*/
int append_list (Sorted_List * List, value_type value, Key_type key){
int result = insert_value(List->tail, value, key) != NULL;
if ( result == SUCCESS){
List->size++;
List->tail = List->tail->sort;
}
return result;
}
int append (Sorted_List * List, value_type value, Key_type key){
return is_empty(List) ? push(List, value, key)
: append_list(List, value, key);
}
/*Function to insert value into list*/
Node * insert_value (Node * node, value_type value, Key_type key){
/*Setting a new node and mallocing it */
Node * new_node = malloc(sizeof(Node));
/*Checking for the new node to not equal null*/
if (new_node != NULL){
/*Setting the values for it*/
new_node->value = value;
new_node->key = key;
/*Setting the new node next to equal old nodes next*/
new_node->sort = node->sort;
/*Setting old node next to equal new node*/
node->sort = new_node;
/////I receive the error around this line^^^^/////
}
return new_node;
}
EDIT::
so here is the code for the push function used in the program
add front's job is to add the values rot the front
and find_prev_gt's job is to find the previes largest valus's location to add the new number
/*Function to push a value to to the front of the list*/
int push (Sorted_List * List, value_type value, Key_type key) {
Node * node = NULL;
int empty = 0;
empty = is_empty(List);
Node * next_node = NULL;
Node * insert_node = find_prev_gt(List->head, key);
int result = FAILURE;
if (insert_node == NULL) {
add_front(&(List->head), value,key);
}
else {
next_node = insert_node->sort;
if (next_node == NULL || next_node->key != key)
insert_value(insert_node, value,key);
}
result = (node != NULL );
/*Returns success if reseult is succesfull*/
if ( result == SUCCESS) {
List->size++;
if (empty)
List->tail = List->head;
}
return result;
}
Node * add_front(Node ** head, value_type value, Key_type key){
Node *new_node = malloc(sizeof(Node));
if (new_node != NULL) {
new_node->key = key;
new_node->value = value;
new_node->sort = *head;
*head = new_node; }
return new_node;
}
/*Function to check if list is empty*/
int is_empty (Sorted_List * list){
return list->head == NULL;
}
Node * find_prev_gt ( Node * head, Key_type key ) {
Node * node = head, * prev = NULL;
while (node != NULL && node->key < key){
prev = node;
node = node->sort;
}
return prev;
}

Answer 1

every time I use the append function, it just crashes
Your problem is in the function push where the value of node does not change after its initialization to NULL, so in
if ( result == SUCCESS) {
List->size++;
if (empty)
List->tail = List->head;
}
the test is always false and the associated code is not executed
You just need to change two lines, replace the line
add_front(&(List->head), value,key);
by
node = add_front(&(List->head), value,key);
and the line
insert_value(insert_node, value,key);
by
node = insert_value(insert_node, value,key);
If I do these two changes and I prefix your code by the definitions
#include <stdlib.h>
#include <stdio.h>
typedef int value_type;
typedef int Key_type;
#define SUCCESS 1
#define FAILURE 0
and add the following main :
int main()
{
Sorted_List list = { 0, 0, 0, 0, 0 };
Node * node;
append(&list, 2, 22);
append(&list, 3, 33);
append(&list, 1, 11);
for (node = list.head; node != NULL; node = node->sort)
printf("[key=%d, value=%d] ", node->key, node->value);
putchar('\n');
return 0;
}
the execution writes :
[key=22, value=2] [key=33, value=3] [key=11, value=1]
Out of that in Sorted_List your code change head and tail but not head_sort nor tail_sort but in Node you set sort but not next, this is not logical, furthermore the nodes are not sorted