After `std::vector b = std::move(a);` where a was non-empty, what is guaranteed about `a`?

It is guaranteed to be empty, because the move constructor always leaves the source cleared.

It is guaranteed to retain its elements, because the move only transfers the buffer pointer.

It is left in a state where any method call is undefined behavior until it is reassigned.

It is in a valid but unspecified state; only operations without preconditions (like clear(), assignment) are safe.

Multiple ChoiceBeginner 45s

Moved-from object guarantees

After `std::vector<int> b = std::move(a);` where a was non-empty, what is guaranteed about `a`?

Options

1It is guaranteed to be empty, because the move constructor always leaves the source cleared.
2It is guaranteed to retain its elements, because the move only transfers the buffer pointer.
3It is left in a state where any method call is undefined behavior until it is reassigned.
4It is in a valid but unspecified state; only operations without preconditions (like clear(), assignment) are safe.

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