managing a list -newbie questions-

Hi everybody,
I'm trying to doan exercise from an old exam of a course I'm following..but I'm stuck with a segmentation fault (with the printf function) and well... I tried many times to modify the code but, so far, I only managed to get a few very strange errors and I really can't understand what's wrong with the functions. Any suggestion? Where am I wrong?
thank you!

Code:

---

#include<stdio.h>
#include<stdlib.h>

typedef struct elemento {
        float valore;
        struct elemento *next;
} Elemento;

typedef Elemento* List;

//Adds an element at the beginning
void Push(List *lista, Elemento e){
        e.next=*lista;
        *lista = &e;
}

//returns the value of the first element
float Read(List lista){
        float pi=lista->valore;
        return pi;
}

//counts the number of elements
int Count(List lista){
if(lista->next==NULL)
        return 1;
int i;
List conta=malloc(sizeof(Elemento));
conta->next=lista->next;
for(i=1;(conta->next)!=NULL;conta=conta->next)
        i++;
free(conta);
return i;
}

main(){
List a=malloc(sizeof(Elemento));
a->valore = 4.0;
a->next = NULL;
List prova=malloc(sizeof(Elemento));
prova->valore=2.0;
prova->next=NULL;
Push(&a,*prova);
float pi=Read(a);
printf("%f\n",pi);
printf("%d\n",Count(a));
}

---

First, you should learn to indent code.

Code:

---

#include<stdio.h>
#include<stdlib.h>

typedef struct elemento {
    float valore;
    struct elemento *next;
} Elemento;

typedef Elemento *List;

//Adds an element at the beginning
void Push(List * lista, Elemento e)
{
    e.next = *lista;
    *lista = &e;
}

//returns the value of the first element
float Read(List lista)
{
    float pi = lista->valore;
    return pi;
}

//counts the number of elements
int Count(List lista)
{
    if (lista->next == NULL)
        return 1;
    int i;
    List conta = malloc(sizeof(Elemento));
    conta->next = lista->next;
    for (i = 1; (conta->next) != NULL; conta = conta->next)
        i++;
    free(conta);
    return i;
}

main()
{
    List a = malloc(sizeof(Elemento));
    a->valore = 4.0;
    a->next = NULL;
    List prova = malloc(sizeof(Elemento));
    prova->valore = 2.0;
    prova->next = NULL;
    Push(&a, *prova);
    float pi = Read(a);
    printf("%f\n", pi);
    printf("%d\n", Count(a));
}

---

The first problem in your code is marked.
You've just set a pointer to a local variable - a variable which is about to go out of scope, and invalidate your pointer.

Thank you! I didn't think about the scope of the poor variable e...well, I've managed to get it working by modifing the code like this:

Code:

---

void Push(List *lista, Elemento e){
        List p =malloc(sizeof(List));
        p->valore = e.valore;
        p->next = *lista;
        *lista = p;
}

---

But I coulnd't think of anything smart leaving "e.next = *lista;" as first line (I mean, I would have to copy that value again because or the variable e)...

Thank you again, hopefully I'll now be able to finish the exercise...