Function xmlTextReaderConstPrefix 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn xmlTextReaderConstPrefix(
    reader: *mut XmlTextReader,
) -> *const xmlChar

const xmlChar *xmlTextReaderConstPrefix(xmlTextReaderPtr reader).

UPSTREAM-PARITY: at an attribute position the prefix comes from the attribute; for a namespace declaration the prefix is reported as “xmlns” (and NULL for the default declaration) — an upstream quirk reproduced here.

SAFETY

• reader must be valid pointers (or NULL where the upstream C contract allows), obtained from the matching constructor/owner and not yet freed; the callee may take or keep ownership exactly as the C API specifies.

The caller must not race this call with concurrent mutation of the same objects from other threads (per-object state is not internally synchronized). Violating any of the above is undefined behavior.

Exercised by the C-API differential courts (courts/suites/data-abi/*-family-probe.c) and the CLI differential courts; those pass byte-for-byte against the upstream oracle.