Function xmlTextReaderIsDefault 

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

int xmlTextReaderIsDefault(xmlTextReaderPtr reader) — whether the current attribute came from the DTD default. The candidate returns 0 for a valid reader (DTD default attribute expansion is not annotated; documented divergence), -1 for a NULL reader (upstream contract).

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.