There are some examples on issue #850 of using this feature, but they
are not easily found from the documentation. Adding them here as an
example makes them more findable and ensures they keep working if the
API changes.
Prevent warnings
- gnu: -Wcomment: multi-line comment
- clang: -Wweak-vtables 'class' has no out-of-line virtual method definitions; its vtable will be emitted in every translation unit
- clang: -Winconsistent-missing-override: 'method' overrides a member function but is not marked 'override'
- MSVC: C4702: unreachable code
