I have noticed that I get error messages or I don't sometimes depending on optimization level. For example, I had a statement that tried to store a value into code space and at opt level zero, I got an error saying that it couldn't convert the lvalue. I understood this. However, at opt level 8, I got no error and in fact the 'optimizer' simply left out the offending line. Why should it do this? If it is an error, it should report it and not throw the code away.