C Doubly Linked List Program -

i have been writing c program work doubly linked lists. not work on dev cpp. can point out error? works until part add new record , crashes. i'm guessing there problem scanf() function.

//c double-linked list program  struct stu {  int roll,ph,ch,ma; stu *plink,*nlink; };  void addstu(stu *p,stu *n) { //add  stu *s; int roll,ph,ch,ma;  printf("hello student!\nyour roll no.? "); scanf("%d",&roll);  printf("\nphysics score? "); scanf("%d",&ph);  printf("\nchemistry? "); scanf("%d",&ch);  printf("\nmath? "); scanf("%d",&ma);  s->roll=roll; s->ph=ph; s->ch=ch; s->ma=ma;  s->plink=p; s->nlink=n; }  void remstu(stu *s) { //remove  stu *next; next->plink=s->nlink; free(s); }  // main function int main() {  stu *s; int choice=0, ct=0;  while(choice!=4) {  printf("\n\t\twelcome records\n\n1. add\n2. remove\n3. see\n4. exit\nenter choice(1-4): "); scanf("%d",&choice);  switch(choice) {      case 1:         stu *t;         addstu(s,t);         s=t;         free(t);         ++ct;         break;      case 2:         remstu(s);         break;      case 3:         for(int i=0;i<ct;++i) {             printf("\n\nroll no. %d\nphysics %d\nchemistry %d\nmath %d",s->roll,s->ch,s->ph,s->ma);             s=s->plink;         }         break;      case 4:         exit(0);         break;      default:         printf("please enter correct choice(1-4)!"); } }  return 0; } 

s->roll=roll; 

the pointer s in function addstu() never initialized , dereferencing leads undefined behavior hence crash.

do

s = malloc(sizeof(struct stu)); /* allocate memory */ 

i hope have

typedef struct stu stu;