Why is unique_ptr operator* not noexcept? [duplicate]

Question

While implementing a basic std library for my hobby OS I came across this and wondered why:

Both operator->() and T* get() are marked as noexcept, however operator*() is not. According to the reference it should be equivalent to *get(), which would allow it to be noexcept and looking at some implementations I see no reason why it is not.

Why is unique_ptr's dereferencing operator not marked as noexcept?

Answer 1

Because operator* for the pointer type of std::unique_ptr may throw. The pointer type alias is defined as:

std::remove_reference<Deleter>::type::pointer if that type exists, otherwise T*. Must satisfy NullablePointer

That may be something other that T*, it may be a class type that overloads operator*.

Answer 2

From cppreference

• typename std::add_lvalue_reference<T>::type operator*() const; (1) (since C++11)
• pointer operator->() const noexcept; (2) (since C++11)

And then:

Exceptions:
1) may throw, e.g. if pointer defines a throwing operator*