Segmentation fault error in Linked-List program - c

Question

I'm facing the segmentation fault error in the following dynamic linked list implementation; GDB shows the issue is on the node = node->next line in the "l_print" function of the linked-list ("LIST_CL.H" file). Anyone can help? I even tried "drawing debug" on paper but still I'm not getting the issue here.
Note: I report the whole code for both the insert and the print, in case it's useful. Therefore LIST.C file include the "switch case 6" to insert the element ("l_add" function in "LIST_CL.H" file) and the "switch case 1" to print the list ("l_print" function in "LIST_CL.H" file)
Note: The issue only happen when the list has one or more items. There's no errors when the list is empty ("list_cl" struct has NULL for both head and tail nodes)
LIST.C:
#include <stdio.h>
#include <string.h> //for strcpy
#include "cl_list.h"
#include "list_cl.h"
#define STRING_SIZE 25
int main(){
list_cl class = L_EMPTYLIST_CL;
puts("Select command:");
puts("0. Exit.");
puts("1. Insert node.");
puts("6. Print all nodes in the linked list.");
int k = 0;
scanf("%d", &k);
while(k != 0){
switch(k){
case 1:
char cf[17] = "";
char first_name[STRING_SIZE] = "";
char last_name[STRING_SIZE] = "";
getchar();
puts("Insert name:");
fgets(first_name, sizeof(first_name), stdin);
puts("Insert surname:");
fgets(last_name, sizeof(last_name), stdin);
puts("Insert fiscal code:");
fgets(cf, sizeof(cf), stdin);
client cliente;
strcpy(cliente.cf, cf);
cliente.first_name = first_name;
cliente.last_name = last_name;
class = l_add_cl(class, cliente);
puts("Node inserted.");
break;
case 6:
l_print(class);
break;
default:
break;
}
scanf("%d", &k);
}
}
LIST_CL.H:
list_cl l_add_cl(list_cl l, client p){
l_node node;
node.id = 1;
node.person = p;
node.next = NULL;
if(l.head == NULL){
//List is empty
l.head = &node;
l.tail = &node;
} else {
l.tail -> next = &node;
l.tail = &node;
}
return l;
}
void l_print(list_cl l){
l_node *node = NULL;
node = l.head;
while(node != NULL){
//client *cliente = &node->person;
//printf("ID Elemento: %d | Name: %s Surname: %s Fiscal Code: %s", node->id, cliente->first_name, cliente->last_name, cliente->cf);
node = node->next; // SEGMENTATION FAULT ERROR HERE!
}
}
CL_LIST.H:
#include "client.h"
typedef struct _node {
unsigned int id;
client person;
struct _node *next;
} l_node;
typedef struct {
l_node *head;
l_node *tail;
} list_cl;
#define L_EMPTYLIST_CL {NULL,NULL}
CLIENT.H:
typedef struct {
char cf[17];
char *first_name;
char *last_name;
} client;

Answer 1

Fixed code:
LIST.C:
#include <stdio.h>
#include <string.h> //for strcpy
#include "cl_list.h"
#include "list_cl.h"
#define STRING_SIZE 25
int main(){
list_cl class = L_EMPTYLIST_CL;
puts("Seleziona un comando:");
puts("0. Exit.");
puts("1. Insert one node.");
puts("6. Print all nodes.");
int k = 0;
scanf("%d", &k);
while(k != 0){
switch(k){
case 1:
char cf[17] = "";
//char first_name[STRING_SIZE] = ""; THIS CAUSE DATA INCONSISTENCY
//char last_name[STRING_SIZE] = ""; THIS CAUSE DATA INCONSISTENCY
char *first_name = malloc(sizeof(char)*STRING_SIZE);
char *last_name = malloc(sizeof(char)*STRING_SIZE);
getchar();
puts("Insert name:");
//fgets(first_name, sizeof(first_name), stdin); ISSUE WITH SIZE OF FIRST_NAME
fgets(first_name, sizeof(char)*STRING_SIZE, stdin);
puts("Insert surname:");
//fgets(last_name, sizeof(last_name), stdin); ISSUE WITH SIZE OF LAST_NAME
fgets(last_name, sizeof(char)*STRING_SIZE, stdin);
puts("IInsert fiscal code:");
fgets(cf, sizeof(cf), stdin);
client *cliente = malloc(sizeof(client));
strcpy(cliente->cf, cf);
cliente->first_name = first_name;
cliente->last_name = last_name;
class = l_add_cl(class, *cliente);
puts("Element inserted.");
break;
case 6:
l_print(class);
break;
default:
break;
}
puts("Select command:");
scanf("%d", &k);
}
}
LIST_CL.H
list_cl l_add_cl(list_cl l, client p){
l_node *node = malloc(sizeof(struct _node));
node->id = 1;
node->person = p;
node->next = NULL;
if(l.head == NULL){
//Empty list
l.head = node;
l.tail = node;
} else {
l.tail -> next = node;
l.tail = node;
l.tail -> next = NULL;
}
return l;
}
void l_print(list_cl l){
l_node *node = NULL;
node = l.head;
while(node != NULL){
client *cliente = &node->person;
printf("ID Element: %d | Name: %s Surname: %s Fiscal code: %s", node->id, cliente->first_name, cliente->last_name, cliente->cf);
node = node->next;
}
}
CL_LIST.H
#include "client.h"
typedef struct _node {
unsigned int id;
client person;
struct _node *next;
} l_node;
typedef struct {
l_node *head;
l_node *tail;
} list_cl;
#define L_EMPTYLIST_CL {NULL,NULL}
CLIENT.H
typedef struct {
char cf[17];
char *first_name;
char *last_name;
} client;