2d dynamic array program crashes - c++

Question

I wrote a dynamically allocated 2D array and for some reason it's not working as I intend it to.
I allocated for a 14x5 array to store values in.
Here is the code:
#include <stdio.h>
#include <stdlib.h>
int main()
{
int i, j, count, count2;
int size, keysize, column;
size = 7; keysize = 10; column = 5;
int row = (size * keysize) / column; // 14
char **arr = (char **)malloc(column * sizeof(char *));
for(i=0; i<row; i++)
arr[i] = (char *)malloc(row * sizeof(char *));
count=0;
count2=0;
for(i=0; i<keysize; i++)
{
for(j=0; j<size; j++)
{
printf("arr[%d][%d]=", count2, count);
arr[count2][count] = 'C';
printf("%c\n", arr[count2][count]);
count++;
if(count == 5)
{
count = 0;
count2++;
}
}
}
return 0;
}
It seems that the program crashes when a value is to be inserted at the location arr[6][0].
Before that it works fine.
I inserted some printf statements to capture this occurring.
I am not sure why it's doing this, the allocation of memory looks fine with me but I am no expert.
Thanks for any help.

Answer 1

change to
char **arr = (char **)malloc(row * sizeof(char *));
for(i=0; i<row; i++)
arr[i] = (char *)malloc(column * sizeof(char));

Answer 2

I notice the question marked with the c++ tag, the clear way to do this in c++ is to use std::vector. So I'm answering this as if it were a C question:
It looks like you haven't allocated enough space here.
column = 5;
char **arr = (char **)malloc(column * sizeof(char *));
This makes space for 5 pointers to rows. Then later on when you are looping:
for(i=0; i<keysize; i++)//note keysize is 10
{
for(j=0; j<size; j++){ // note size is 7
arr[count2][count];
count++;
if(count == 5){
count = 0;
count2++;//gets incremented every time the inner loop runs
}
}
}
Because count2 gets incremented every time the inner loop runs it will get as big as keysize eventually. That means that arr[keysize][0] must be valid, which it isn't because you in effect made arr[5][14]. The first failure is when you call arr[6][0] which accesses past the end of the array and causes your program to crash.
If the intent here is to initialize variables then to fix this you probably want to loop over the same values for dimensions that you used for allocating the memory.