Consider the following program, written in C:

typedef struct

{

int x;

int y;

} Foo;

void allocate_node (Foo * f)

{

f = (Foo *) malloc ( sizeof(Foo) );

}

void main ()

{

Foo * p;

allocate_node (p);

p->x = 2;

p->y = 3;

free(p);

}

Although the program compiles, it produces a run-time error. Why?

Rewrite the two functions allocate_node and main so that the program runs correctly.