size of a datatype without using sizeof

Question

I have a data type, say X, and I want to know its size without declaring a variable or pointer of that type and of course without using sizeof oper

Answer 1

# include

struct node
{
  int a;
  char c;
};

void main()
{
   struct node*ptr;
   ptr=(struct node*)0;
   printf("%d",++ptr);
}