[TorKlingberg]

It's quite common in embedded systems to have the fault handler end with an infinite loop, to give the programmer a chance to attach a debugger an inspect the call stack. Sometimes this behavior is turned on or off with a debug flag, which can trigger this unexpected optimization if the flag is not a compile time constant.

[pcvarmint]

A halt instruction (HLT on x86) might also work.

[planteen]

You could also add a volatile declaration

[boomlinde]

You could always say

    if (flag) while (1);

[TorKlingberg]

Yes, that would make more sense. I have never seen this optimization actually bite anyone.