Function xmlParserInputBufferCreateFilenameDefault 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn xmlParserInputBufferCreateFilenameDefault(
    func: Option<unsafe extern "C" fn(*const c_char, c_int) -> *mut _xmlParserInputBuffer>,
) -> Option<unsafe extern "C" fn(*const c_char, c_int) -> *mut _xmlParserInputBuffer>

xmlParserInputBufferCreateFilenameDefault.

xmlParserInputBufferCreateFilenameFunc
xmlParserInputBufferCreateFilenameDefault(xmlParserInputBufferCreateFilenameFunc func);

UPSTREAM-PARITY: comparing the registered callback against the default function pointer to decide reset-vs-replace mirrors upstream globals.c; on ELF platforms the address of a symbol is stable and unique within the DSO.