C Linked List from file not exiting after printing - c

Question

So, I have to print a linked list from a file input, which I've managed to get working:
#include <stdio.h>
#include <stdlib.h>
typedef struct Vehicle{
int option;
char make [30];
char model[30];
int car_manufacture_date;
float maximum_velocity;
float mass;
int seats;
struct Vehicle *next;//linked list node
} vehicle_t;
int main (){
FILE* fp;
fp = fopen("vehicles.crash.txt", "r");
vehicle_t* first_car = malloc(sizeof(vehicle_t));
if (first_car == NULL){
printf("Error. Failed to allocate memory to first_car\n");
exit(1);
}
vehicle_t* current_vehicle = malloc(sizeof(vehicle_t));
if (current_vehicle == NULL){
printf("Error. Failed to allocate memory to current_vehicle\n");
exit(1);
}
vehicle_t* new_vehicle = malloc(sizeof(vehicle_t));
if (new_vehicle == NULL){
printf("Error. Failed to allocate memory to new_vehicle\n");
exit(1);
}
printf("GOOD1\n");
current_vehicle = first_car;
new_vehicle = first_car;
printf("GOOD2\n");
//Loading vehicles from file to linked list
if (fp != NULL)
{
printf("GOOD3\n");
while (fscanf(fp,"%d %s %s %d %f %f %d", &new_vehicle->option, new_vehicle->make, new_vehicle->model, &new_vehicle->car_manufacture_date,
&new_vehicle->maximum_velocity, &new_vehicle->mass, &new_vehicle->seats) != EOF)
{
printf("GOOD4\n");
current_vehicle->next = new_vehicle;
current_vehicle = current_vehicle->next;
new_vehicle = malloc(sizeof(vehicle_t));
if (first_car == NULL){
printf("Error. Failed to allocate memory\n");
new_vehicle->next=NULL;
exit(1);
}
printf("GOOD5\n");
}
close(fp);
printf("Input completed\n");
}
else
printf("Error! couldn't find file\n");
current_vehicle = first_car;
while (current_vehicle != NULL)
{
printf("Option: %d\tMake: %s\tModel: %s\tManufactured: %d\tMax Velocity: %.2f\tMass: %.2f\tSeats: %d\n",
current_vehicle->option, current_vehicle->make, current_vehicle->model, current_vehicle->car_manufacture_date,
current_vehicle->maximum_velocity, current_vehicle->mass, current_vehicle->seats);
new_vehicle = current_vehicle->next;
current_vehicle = current_vehicle->next;
};
printf("Printing completed");
return 0;
}
Everything works fine right until the last file item is printed out, after which the program crashes. From what I've seen in other posts, the while loop matches them all.
The printed "GOOD" statements are just checkpoints
The text in the file is formatted as: 1 Toyota Camry 2010 200.0 1100.0 5

Answer 1

I think you forget to set the ->next field of the last list node to NULL. You just called malloc, so the value could be anything random, making your printing failed.

Answer 2

The main reason for the infinite loop was failing to set the final next to NULL [as others have mentioned].
But, I think this is easier to see with the code simplified as yours, although mostly correct, was more complicated than it needed to be.
Anyway, this compiles but I didn't test it [please pardon the gratuitous style cleanup]:
#include <stdio.h>
#include <stdlib.h>
typedef struct Vehicle {
int option;
char make[30];
char model[30];
int car_manufacture_date;
float maximum_velocity;
float mass;
int seats;
struct Vehicle *next; // linked list node
} vehicle_t;
int
main()
{
FILE *fp;
fp = fopen("vehicles.crash.txt", "r");
if (fp == NULL) {
printf("Error! couldn't find file\n");
exit(1);
}
vehicle_t *first_car = NULL;
vehicle_t *previous_vehicle = NULL;
// Loading vehicles from file to linked list
while (1) {
vehicle_t *new_vehicle = malloc(sizeof(vehicle_t));
if (new_vehicle == NULL) {
printf("Error. Failed to allocate memory to new_vehicle\n");
exit(1);
}
// NOTE: the lack of this [in your equivalent code] was the reason
// for the infinite loop
new_vehicle->next = NULL;
if (fscanf(fp, "%d %s %s %d %f %f %d",
&new_vehicle->option, new_vehicle->make, new_vehicle->model,
&new_vehicle->car_manufacture_date, &new_vehicle->maximum_velocity,
&new_vehicle->mass, &new_vehicle->seats) == EOF) {
free(new_vehicle);
break;
}
if (first_car == NULL)
first_car = new_vehicle;
else
previous_vehicle->next = new_vehicle;
previous_vehicle = new_vehicle;
}
fclose(fp);
vehicle_t *current_vehicle = first_car;
while (current_vehicle != NULL) {
printf("Option: %d\tMake: %s\tModel: %s\tManufactured: %d\tMax Velocity: %.2f\tMass: %.2f\tSeats: %d\n",
current_vehicle->option, current_vehicle->make,
current_vehicle->model, current_vehicle->car_manufacture_date,
current_vehicle->maximum_velocity, current_vehicle->mass,
current_vehicle->seats);
current_vehicle = current_vehicle->next;
};
printf("Printing completed");
return 0;
}