Boost
C++ Libraries
...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Boost
C++ Libraries
...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
When an optional object that contains a value is moved from (is a source of move constructor or assignment) it still contains a value and its contained value is left in a moved-from state. This can be illustrated with the following example.
optional<std::unique_ptr<int>> opi {std::make_unique<int>(1)}; optional<std::unique_ptr<int>> opj = std::move(opi); assert (opi); assert (*opi == nullptr);
Quite a lot of people expect that when an object that contains a value
is moved from, its contained value should be destroyed. This is not so,
for performance reasons. Current semantics allow the implementation of
boost::opiotnal<T>
to be trivially copyable when T
is trivial.