Method takeOwnership

tests/catch.hpp:11219–11226

    }

    void StringRef::takeOwnership() {
        if( !isOwned() ) {
            m_data = new char[m_size+1];
            memcpy( m_data, m_start, m_size );
            m_data[m_size] = '\0';
            m_start = m_data;
        }
    }
    auto StringRef::substr( size_type start, size_type size ) const noexcept -> StringRef {
        if( start < m_size )
            return StringRef( m_start+start, size );