Infinite loop when adding 1 character to a list - c

Question

I am writting a program which adds a character to a list. The problem is that when I have my original list of 5 nodes and I try to add another, everything works, but than when I try to add another one the stampa function becomes infinite.
I can not find the bug. Any help would be welcomed. Here is the code:
struct nodo {
char c;
struct nodo *next;
};
typedef struct nodo *lista;
void mc_coda(lista *l, char el);
void stampa(lista nodo01);
int main() {
int test[5] = {0, 1, 1, 0, 1};
lista nodo01 = malloc(sizeof(struct nodo));
lista nodo02 = malloc(sizeof(struct nodo));
lista nodo03 = malloc(sizeof(struct nodo));
lista nodo04 = malloc(sizeof(struct nodo));
lista nodo05 = malloc(sizeof(struct nodo));
(*nodo01).next = nodo02;
(*nodo02).next = nodo03;
(*nodo03).next = nodo04;
(*nodo04).next = nodo05;
(*nodo05).next = NULL;
(*nodo01).c = 'a';
(*nodo02).c = 'b';
(*nodo03).c = 'c';
(*nodo04).c = 'd';
(*nodo05).c = 'e';
mc_coda(&nodo01, 'e');
mc_coda(&nodo01,
'f'); // If this line is removed everything workd fine, if this line
// if added that it prints infinite f
stampa(nodo01);
return 0;
}
void mc_coda(lista *l, char el) {
if ((*l) == NULL) {
struct nodo temp;
temp.next = NULL;
temp.c = el;
(*l) = &temp;
} else {
while ((*l) != NULL) {
l = &(*(*l)).next;
}
struct nodo temp;
temp.next = NULL;
temp.c = el;
(*l) = &temp;
}
}
void stampa(lista nodo01) {
while (nodo01 != NULL) {
printf("%c\n", (*nodo01).c);
nodo01 = (*nodo01).next;
}
}

Answer 1

Your implementation of mc_coda creates a local variable temp. Because temp is a local variable it will go out of scope when the function exits and then the space will be reused. Instead, you need to allocate space on the heap with malloc. See the below implementation of mc_coda for an example of how to do that:
#include <stdio.h>
#include <stdlib.h>
struct nodo {
char c;
struct nodo *next;
};
typedef struct nodo *lista;
void mc_coda(lista *l, char el);
void stampa(lista nodo01);
int main() {
lista nodo01 = malloc(sizeof(struct nodo));
lista nodo02 = malloc(sizeof(struct nodo));
lista nodo03 = malloc(sizeof(struct nodo));
lista nodo04 = malloc(sizeof(struct nodo));
lista nodo05 = malloc(sizeof(struct nodo));
(*nodo01).next = nodo02;
(*nodo02).next = nodo03;
(*nodo03).next = nodo04;
(*nodo04).next = nodo05;
(*nodo05).next = NULL;
(*nodo01).c = 'a';
(*nodo02).c = 'b';
(*nodo03).c = 'c';
(*nodo04).c = 'd';
(*nodo05).c = 'e';
mc_coda(&nodo01, 'e');
mc_coda(&nodo01, 'f');
stampa(nodo01);
return 0;
}
void mc_coda(lista *l, char el) {
lista tmp = malloc(sizeof(struct nodo));
tmp->next = NULL;
tmp->c = el;
if ((*l) == NULL) {
(*l) = tmp;
} else {
while ((*l) != NULL) {
l = &(*(*l)).next;
}
(*l) = tmp;
}
}
void stampa(lista nodo01) {
while (nodo01 != NULL) {
printf("%c\n", (*nodo01).c);
nodo01 = (*nodo01).next;
}
}