Error Message
comma operator within array index expression
When a comma occurs in an array index expression, the compiler uses the value after the last comma.
Example
The following sample generates C4709:
// C4709.cpp
// compile with: /W4
#include <stdio.h>
int main()
{
int arr[2][2];
arr[0][0] = 10;
arr[0][1] = 11;
// Prints 10, not 11
printf_s("\n%d",arr[0][1,0]); // C4709
}