boost::urls::url::url Constructor Synopsis Declared in header <boost/url/url.hpp> url() noexcept; Description Default constructed urls contain a zero-length string. This matches the grammar for a relative-ref with an empty path and no query or fragment. url u; this->empty() == true Constant. Throws nothing. relative-ref = relative-part [ "?" query ] [ "#" fragment ] 4.2. Relative Reference (rfc3986)