/usr/include/msgpack/v2/adaptor/ is in libmsgpack-dev 2.1.5-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/msgpack/v2/adaptor/adaptor_base.hpp
/usr/include/msgpack/v2/adaptor/adaptor_base_decl.hpp
/usr/include/msgpack/v2/adaptor/array_ref_decl.hpp
/usr/include/msgpack/v2/adaptor/boost/
/usr/include/msgpack/v2/adaptor/boost/msgpack_variant_decl.hpp
/usr/include/msgpack/v2/adaptor/check_container_size_decl.hpp
/usr/include/msgpack/v2/adaptor/define_decl.hpp
/usr/include/msgpack/v2/adaptor/detail/
/usr/include/msgpack/v2/adaptor/detail/cpp03_define_array_decl.hpp
/usr/include/msgpack/v2/adaptor/detail/cpp03_define_map_decl.hpp
/usr/include/msgpack/v2/adaptor/detail/cpp03_msgpack_tuple_decl.hpp
/usr/include/msgpack/v2/adaptor/detail/cpp11_define_array_decl.hpp
/usr/include/msgpack/v2/adaptor/detail/cpp11_define_map_decl.hpp
/usr/include/msgpack/v2/adaptor/detail/cpp11_msgpack_tuple_decl.hpp
/usr/include/msgpack/v2/adaptor/ext_decl.hpp
/usr/include/msgpack/v2/adaptor/fixint_decl.hpp
/usr/include/msgpack/v2/adaptor/int_decl.hpp
/usr/include/msgpack/v2/adaptor/map_decl.hpp
/usr/include/msgpack/v2/adaptor/msgpack_tuple_decl.hpp
/usr/include/msgpack/v2/adaptor/nil_decl.hpp
/usr/include/msgpack/v2/adaptor/raw_decl.hpp
/usr/include/msgpack/v2/adaptor/size_equal_only_decl.hpp
/usr/include/msgpack/v2/adaptor/v4raw_decl.hpp