Why is `std::unique_ptr ` non-copyable but movable?

Because its destructor is implicitly deleted, which in turn deletes the copy constructor and copy assignment.

Because it holds an atomic reference count that cannot be copied, so only the count may be transferred.

Copying would duplicate ownership of the same deletable resource; moving transfers the sole pointer value.

It is in fact copyable, but only when instantiated with a deleter that is itself non-copyable.

Multiple ChoiceBeginner 45s

unique_ptr is not copyable

Why is `std::unique_ptr<T>` non-copyable but movable?

Options

1Because its destructor is implicitly deleted, which in turn deletes the copy constructor and copy assignment.
2Because it holds an atomic reference count that cannot be copied, so only the count may be transferred.
3Copying would duplicate ownership of the same deletable resource; moving transfers the sole pointer value.
4It is in fact copyable, but only when instantiated with a deleter that is itself non-copyable.

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