Optimizing away a “while(1);” in C++0x

Question

Updated, see below!

I have heard and read that C++0x allows an compiler to print \"Hello\" for the following snippet

#include 

        

Answer 1

It is not decidable for the compiler for non-trivial cases if it is an infinite loop at all.

In different cases, it can happen that your optimiser will reach a better complexity class for your code (e.g. it was O(n^2) and you get O(n) or O(1) after optimisation).

So, to include such a rule that disallows removing an infinite loop into the C++ standard would make many optimisations impossible. And most people don't want this. I think this quite answers your question.

---

Another thing: I never have seen any valid example where you need an infinite loop which does nothing.

The one example I have heard about was an ugly hack that really should be solved otherwise: It was about embedded systems where the only way to trigger a reset was to freeze the device so that the watchdog restarts it automatically.

If you know any valid/good example where you need an infinite loop which does nothing, please tell me.