XML_SetBase
XML_SetBase(XML_Parser parser, const XML_Char *base);
if (XML_SetBase(g_parser, base) == XML_STATUS_ERROR) {
if (XML_SetBase(g_parser, new_base) == XML_STATUS_OK)
if (XML_SetBase(g_parser, new_base) != XML_STATUS_OK)
if (XML_SetBase(g_parser, NULL) != XML_STATUS_OK)
XML_SetBase(g_parser, old_base);