Unhandled exception when adding a value to struct member in 2D array

Question

I am writing a Theater program using a dynamic 2D array. To store a booking details I use structure. When I try to initialize one of the variables inside each index of 2D array, I receive unhandled exception error.

Function with error:

void initializing_tickets(ticket **arrayPtr, int row, int col){
int i, j, counter;

for(i = 0; i < row; i++)
{
    for(j = 0; j < col; j++)
    {
        (*(arrayPtr + i) + j) -> id = 0; // debugger explains that expression cannot be evaluated
        printf("%d ", (*(arrayPtr + i) + j) -> id);
    }
    printf("\n");
    } 
} //end of initializing_tickets()

My program so far:

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

/* Structures */
typedef struct Theater
{
   int id;
   int status;
   char name[20];
   char phone[15];

 } ticket;


 /* Global variables */

 ticket **array2D; // pointer to a 2D array


 /* Constructors */
 void create_Theater(int *row, int* col);
 void test();
 void loop_array(ticket **arrayPtr, int row, int col);
 void initializing_tickets(ticket **arrayPtr, int row, int col);

 int main(void)
 {
    int row = 0, col = 0;
    create_Theater(&row,&col);
    initializing_tickets(array2D, row, col);
    //loop_array(array2D, row, col);
    //test();



   printf("\n\n");
   system("pause");
   return(0);
 }

void create_Theater(int *row, int* col)
{
    int r = 0, c = 0;
    int i;
    assert(row);
    assert(col);

    *row = r;
    *col = c;

    printf("Please enter the row dimensions of the Theater\n");
    scanf("%d", row);

    printf("Please enter the column dimensions of the Theater\n");
    scanf("%d", col);

    array2D = (ticket**)malloc(r*sizeof(ticket*));
    for (i = 0;i<r;i++)
    {
        array2D[i] = (ticket*)malloc(c*sizeof(ticket));
    }

} // end of create_Theater()

void initializing_tickets(ticket **arrayPtr, int row, int col){
int i, j, counter;

for(i = 0; i < row; i++)
{
    for(j = 0; j < col; j++)
    {
        (*(arrayPtr + i) + j) -> id = 0; // debugger explains that expression cannot be evaluated
        printf("%d ", (*(arrayPtr + i) + j) -> id);
    }
    printf("\n");
    } 
} //end of initializing_tickets()

void loop_array(ticket **arrayPtr, int row, int col)
{

    int i, j;

    for(i = 0; i < row; i++)
    {
        printf("Row is ok");
        for(j = 0; j < col; j++)
        {
            printf("Col is ok");
        }
    } 
}

I think array is not allocated properly to a memory, but I can't find a mistake. Thank you for attention!

I found 1 mistake! It's in void create_Theater(int row, int col). I did a check with printf("Row: %d\n", r); printf("Col: %d\n", c); and it returned me 0 0, means there is no values stored. And I use those in array2D = (ticket**)malloc(rsizeof(ticket)); . How do I pass dimension values entered by user via pointers in this situation? — GarRudo
– GarRudo, Commented Mar 14, 2016 at 11:40
You should use proper 2D arrays instead of this pointer-to-pointer thing. So much easier to read and maintain. Code like (*(arrayPtr + i) + j) is very questionable. — Lundin
– Lundin, Commented Mar 14, 2016 at 12:08
But dynamic memory allocation assumes that you are using a pointers. If I was making static array, then there is no need for pointers. Pointer to pointer is for accessing 2nd dimension of the array. — GarRudo
– GarRudo, Commented Mar 14, 2016 at 12:15

EmJiHash · Accepted Answer · 2016-03-14 11:38:00Z

2

Change your function to:

void create_Theater(int* row, int* col){
   int i;
   assert(row);
   assert(col);

   printf("Please enter the row dimensions of the Theater\n");
   scanf("%d", row);

   printf("Please enter the column dimensions of the Theater\n");
   scanf("%d", col);

   array2D = (ticket**)malloc((*row)*sizeof(ticket*));
   for (i = 0;i<(*row);i++)
   {
      array2D[i] = (ticket*)malloc((*col)*sizeof(ticket));
   }
} // end of create_Theater()

It works.

answered Mar 14, 2016 at 11:38

EmJiHash

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