There is absolutely no problem with optimizations being available. The problem is that the standard gives the compiler license to muck with the semantics of the program in highly non-intuitive and potentially dangerous ways, and this is true regardless of what flags are passed to the compiler. So I can't depend on anything working even if I specify -O0, at least not by the standard. I am entirely at the mercy of the benevolence of my compiler vendor.

If the compiler is going to be given license to make those kinds of dangerous non-intuitive changes to the program semantics I want that to be evident in the source code. For example, I would like to have to say something like YOU_MAY_ASSUME(NOTNULL(X)) before the compiler can assume that X is a pointer that can be dereferenced without signaling an error if it's null. That way the optimizations are still available, but it is easy to tell by looking at the source code if the author prioritized speed over safety and if there are potential gotchas hiding in the code as a result. The way it is now, the potential gotchas are like hidden land mines, nearly impossible to see, and ready to blow you to bits (pun intended :-) without warning.