Are there risks to optimizing code in C#?

Question

In the build settings panel of VS2010 Pro, there is a CheckBox with the label \"optimize code\"... of course, I want to check it... but being unusually cautious, I asked my

Answer 1

It is possible that some bugs will occur when running in release mode that do not otherwise occur. The infamous "non-volatile flag" comes to mind:

flag = false;

Thread t = new Thread(
   o =>
   {
        while(!flag)
        {
           // do stuff
        }
   });
t.Start();

// main thread does some work

flag = true;
t.Join(); // will never return in release mode if flag is not volatile

This happens because of compiler optimizations, as the flag variable gets cached by the core of thread t and thus it cannot see the updated value of flag.