Just because it works doesn't mean it's right. When you smash your stack, you invoke undefined behavior. The program may seem to work fine, but there is definitely a problem, and depending on the circumstances, the problem may manifest itself in other unforeseen ways.
Since you are receiving this message, the debugger is protecting you from some of the damage by surrounding your stack with its buffer zone, but in a release build, you'll probably get random unexplained crashes.
Why don't you post the code from your function and see if we can come up with the reason? The debugger should give you a hint that it is "around the variable 'gamechoice'". This is a valuable clue. Perhaps the variable before 'gamechoice' is an array and you are assigning a variable to the array that is out-of-bounds. Perhaps the variable after 'gamechoice' is an array and is being indexed with a negative value. Perhaps 'gamechoice' itself is the problem.