How to walk through array of Struct in c - c

Question

I have a program which creates an array or struct and go through it for processing. Initially it initialize the array with the defined nyumber of elements. Then for some number of element in array, the name is assigned.
I pretend the code that is equal to my scenario which is tested in codebloc and get the similar error. The problem is described in comments.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct _car {
char *name;
int year;
} Car;
char *getCarName(char *name, int var);
void processCar();
void printCars(Car car[]);
int INCREMENT = 10;
int main(void)
{
processCar();
return 0;
}
void processCar()
{
// create car array with amount of INCREMENT
Car CAR_ARRAY[INCREMENT];
int a=0;
// This function assign name for Car amount 10 less than INCREMENT
while (a<INCREMENT - 2) {
char *carName;
carName = getCarName(&carName, a);
CAR_ARRAY[a].name = malloc(strlen(carName) + 1);
strcpy(CAR_ARRAY[a].name, carName);
a++;
}
printCars(CAR_ARRAY);
}
void printCars(Car car[])
{
printf("IN Car \n");
int a = 0;
// when try to call name for car amount equals to INCREMENT program terminates.
while(a<INCREMENT) {
if (car[a].name != NULL) // checking if NULL
printf("Car Name : %d -> %s\n", a, car[a].name);
a++;
}
}
char *getCarName(char *name, int var)
{
name = "Toyota";
return name;
}
What is the right way to check the struct value on struct array whether it can be called?
EDIT
I created a hack to do this as follows.
// added these right after creating array
for (a = 0; a < INCREMENT; a++)
CAR_ARRAY[a].name = NULL;
I dont know if it is a standard way or not. pls advice.

Answer 1

You are checking for NULL before printing, which is a good idea, but it doesn't help you here, because your last two cars are uninitialised and likely contain garbage: The name pointer is not NULL, but doesn't point to a valid address either. Segmentation violation ensues.
You should initialise all cars, not only INCREMENT - 2. Alternatively, you could initialise your cars to zero by calling memset before your initialisation:
memset(CAR_ARRAY, 0, sizeof(Car) * INCREMENT);
As an aside, the way you deal with getCarName is rather shaky as well. At the moment, your name is a pointer to a string literal. Your local variable carName does a half-hearted double duty: You try to pass it by reference (but essentially you don't) and you also return it.
Basically, you could do this in one of two ways. The easier one here is to return a pointer. in that case, you don't have to pass any string:
char *getCarName(int var)
{
static char *names[3] = {"Toyota", "Dodge", "Peugeot"};
return names[var % 3];
}
and call it like so:
char *carName = getCarName(&carName, a);
Alternatively, you could pass a char pointer by reference, i.e. as pointer to pointer to char. In that case, you don't have to return anything:
void getCarName(char **name, int var)
{
static char* names[3] = {"Toyota", "Dodge", "Peugeot"};
*name = names[var % 3];
}
Call it like so:
char *carName;
getCarName(&carName, a);
There are other scenarios here, for example if you just pass a char pointer and have getCarName fill it, but I'll leave that for now - it would make everything even more complicated.