Deleting in linked lists? - c

Question

I wrote the following code:
#include<stdio.h>
struct student{
char name[25];
double gpa;
struct student *next;
};
struct student *list_head;
struct student *create_new_student(char nm[], double gpa)
{
struct student *st;
printf("\tcreating node\t");
printf("\nName=%s \t Gpa= %.2f\n", nm, gpa);
st = (struct student*)malloc(sizeof (struct student ));
strcpy(st->name, nm);
st->gpa = gpa;
st->next = NULL;
return st;
}
void printstudent(struct student *st)
{
printf("\nName %s,GPA %f\n", st->name, st->gpa);
}
void insert_first_list(struct student *new_node)
{
printf("\nInserting node: ");
printstudent(new_node);
new_node->next = list_head;
list_head = new_node;
}
struct student *delete_first_node()
{
struct student *deleted_node;
printf("\nDeleting node: ");
printstudent(deleted_node);
list_head = list_head->next;
return deleted_node;
}
void printlist(struct student *st)
{
printf("\nPrinting list: ");
while(st != NULL) {
printstudent(st);
st = st->next;
}
}
int main()
{
struct student *other;
list_head = create_new_student("Adil", 3.1);
other = create_new_student("Fatima", 3.8);
insert_first_list(other);
printlist(list_head);
other = delete_first_node();
printlist(list_head);
return 0;
}
When I run it, there are no errors or warnings. However, it stops at the delete part.The message says the program has stopped working.
Can you please help me find the problem?

Answer 1

In function delete_first_node the node deleted_node is not initialized and passed to function printstudent which try to access its member, results in undefined behavior.
The function should be
struct student *delete_first_node(){
struct student *deleted_node = list_head;
printf("\nDeleting node: ");
if(deleted_node != NULL)
{
printstudent(deleted_node);
list_head= list_head->next;
free(deleted_node);
}
else
printf("List is emty\n");
return list_head;
}