Thread: How to search in a stack and a linked list?

I need to search elements of a stack and a linked list. I implemented stack using linked list I have search both function to do it.

Code:

struct student{
    char name[100];
    char surname[100];
    char roll[10];
    char department[50];
    struct student *next;
};
 
struct theStack{
    struct student *head;
    struct student *pop;
    struct student st;
};
 
struct theStack myStack;
 
void search_both(){
     struct student *a;
     struct theStack *x;

     a=(struct student*)malloc(sizeof *a);
     x=(struct theStack*)malloc(sizeof *x);

        while(strcmp(a->name, x->st.name)==0){
            while(strcmp (a->surname, x->st.surname)==0){
                printf("%s %s and %s %s taking both classes",a->name, a->surname,x->st.name,x->st.surname);
                a=a->next;
                x=x->st.next;
            
        }
     }
     free(a);
     free(x);
}

what must be the wrong part of my code?