Function xmlXPathOrderDocElems 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn xmlXPathOrderDocElems(
    doc: *mut _xmlDoc,
) -> c_long

XML_INTPTR_T xmlXPathOrderDocElems(xmlDocPtr doc) (2.15 signature) — indexes the document’s elements in document order: each element’s content field is set to -(n) where n is its 1-based document-order position, and the total element count is returned (-1 for NULL).

UPSTREAM-PARITY

Upstream 2.13+ changed the return type from xmlNodeSetPtr to XML_INTPTR_T (long). The element content slots are repurposed as the document-order index (XML_INT_TO_PTR(-count)).

SAFETY

• doc must be a valid document or NULL.