c - Sorting a linked list in an ascending way -

i trying write function inserts numbers(from user)to nodes (1 number each node) , sorts them in ascending way. wrote function:

void insertnode(struct n_node *head) {     struct n_node *temp = head;     int number;     printf("please insert number node\n");     scanf("%d", &number);     while (number != sentry)     {         while ((temp->next != null) && (temp->next->num < number))         {             temp = temp->next;         }         struct n_node *addnode = (struct n_node*)malloc(sizeof(struct n_node));         addnode->num = number;         if (temp->next == null && number < temp->num)         {             addnode->next = temp;             head = addnode;         }         else         {             addnode->next = temp->next;             temp->next = addnode;         }         temp = head;         scanf("%d", &number);     }     options(); } 

it compiles right after insert first number stops, gives me break message , points on line:

while ((temp->next != null) && (temp->next->num < number)) 

nothing appears on error list, appreciated, thanks!

in algorithm, not testing special cases in correct order:

• if list empty, head null , test temp->next != null invokes undefined behaviour.
• if number smaller number in first node, there no need try , iterate on list, node needs inserted @ head.

you should first allocate new node , check special cases single test:

 struct n_node *addnode = malloc(sizeof(struct n_node));  addnode->num = number;   if (head == null || number < head->num) {      addnode->next = head;      head = addnode;  } 

otherwise, iteration loop correct , node inserted after temp when reach false condition:

    while (temp->next != null && temp->next->num < number) {         temp = temp->next;     }     addnode->next = temp->next;     temp->next = addnode; 

the loop becomes simpler:

void insertnode(struct n_node **headp) {     struct n_node *head = *headp;     int number;     printf("please insert number node\n");      while (scanf("%d", &number) == 1 && number != sentry) {         struct n_node *addnode = malloc(sizeof(struct n_node));         if (addnode == null) {             printf("out of memory\n");             return;         }         addnode->num = number;          if (head == null || number < head->num) {             addnode->next = head;             *headp = head = addnode;         } else {             struct n_node *temp = head;             while (temp->next != null && temp->next->num < number) {                 temp = temp->next;             }             addnode->next = temp->next;             temp->next = addnode;         }     }     options(); // head not passed function? } 

also note change in api allow function update list head in caller's scope, change stop scanning numbers upon end of file or non number input in addition magic number.