why the TiXmlNode ::clear can not clear!??

[daixiaofei]

my code is that:
while((m_TXmlDoc->FirstChild()->ToDeclaration())!=NULL)
    {
        m_TXmlDoc->FirstChild()->Clear();
        m_TXmlDoc->Print(stderr);
    }
when I run ,,it show that the clear ,does not work?!