When exactly does an object cast with std::moved get moved?
For instance, does the following code constitute use after move?
f(std::move(a), a.Something())
Where f = f(A a, int x) and a is an instance of some class.
I understand that std::move(a) may be evaluated before or after a.Something(), but (since std::move is just a cast) when does the actual move occur?
This line:
f(std::move(a), a.Something());
Can indeed constitute a use after move.
If your f is:
f(A a, int x) { ... }
Then the first argument will have to be either copied or moved into the parameter A a before invoking f. This means that the actual move can also take place before a.Something() is evaluated, causing a use after move.
It's worth nothing that if your f was e.g.:
f(A && a, int x) { ... }
Then you would be safe, because std::move itself is just a cast to rvalue ref which is what is expected for A && a, and therefore no move would actually take place at the stage of evaluating the arguments for f.