Switch inside For loop - Getting weird results in Release mode

Question

Is there anything speaking against a structure like to following. In Release mode, Visual Studio seems to ignore i < 10 and execute the loop without end. If I set a break point I see that i runs from 0 to 9 and stays at 9 in all further iterations. If I printf i, I get a error after the 10 iteration, because arr only has 10 fields. Very strange. Please help.

for (i = 0; i < 10; i++){
  switch (arr[i].type1){
     case A:
        //something  
        break;

     case B:
        switch (arr[i].type2){
         //something
        }
        break;

     default:
        break;
  }
}

Thanks!

---

EDIT: I removed all switch statements and replaced them with if statements. Work perfectly now. I still have difficulty believing that I was right and Visual Studio wrong. What about all my other Switch statements in the program? :/

Answer 1

Change the loop variable to j and make the first line of the loop:

int i = j;

Does it still do it?

Answer 2

I suspect that

 // something

might have something to do with it. If you run this code as is (with the actual case code removed) -- does it happen?

How about if you take the entire switch and put it in a function?

You might be changing i somewhere in that // something either directly, or by some memory bounds issue.

Answer 3

nothing wrong with your example. Perhaps you have some accidental stack-overwriting or something like that in other parts of your code that introduce weird side effects in that place (and no sense making debugging sessions)?

Answer 4

As long as I don't know what // something does, I'll just give you the best idea I have given what I know;

If this only occurs in release mode, I would guess that the optimization done by the compiler may be the cause if this odd behaviour.

If you can make this occur reliably with the exact code given above, I'd say you should try turning off optimization and see if that helps.