typedef struct str{
   char* ptr;
}str_t;

copy(str_t t){
  char a[12];
  char *p;
  char *ptr;


  printf("t= %s p = %d ptr = %d\n", t, p, ptr);
 
  strcpy(a, t.ptr);
  printf("a = %s %u\n", a, &a);

  strcpy(ptr, t.ptr);
  printf("ptr = %s %u\n", ptr, &ptr);

  p= t.ptr;
  printf("p = %s %u",p, &p);

}
main ()
{
str_t t;
char app[] = "hello";
char ap[] ="world";

t.ptr = ap;
copy(t);

printf("%s", app);
}

Segmentation fault