Ensuring a Program Written for 32-bit Windows is Compatible with 64-bit Windows

struct GPoint
{
  int x;
  int y;
}

// Array of twenty GPoints
GPoint[] myArr = malloc(20 * sizeof(GPoint);

GPoint* myPointer = myArr;
int index = GetIndexAffectedPoint();

// Invert X and Y for the point
myPointer += 8*index;
swap(myPointer);