Obtain an executor with the blocking.possibly property.

basic_system_executor< execution::blocking_t::possibly_t, Relationship, Allocator > require(
    execution::blocking_t::possibly_t ) const;

Do not call this function directly. It is intended for use with the require customisation point.

For example:

boost::asio::system_executor ex1;
auto ex2 = boost::asio::require(ex1,
    boost::asio::execution::blocking.possibly);