void do_something() throw();
This is a guarantee from the implementer's side that the function will never throw an exception. That is what a client of the function can expect. However, it also means any exception generated somewhere inside the function is handled and not rethrown back to the parent of do_something(). Shame on he who re-throw-eth from within, for there is nothing that'll stop him from throwing. This is because, throwing from within a function with an empty exception-specification is equivalent to throwing an exception not mentioned in the specification and making the std::unexpected() is to be expected followed by program termination.
BTW: The generally accepted definition of strong exception guarantee is: If a public operation fails for some reason, an exception is thrown, and the object's state is left unchanged (atomic operation).
