pub unsafe extern "cdecl" fn UCNV_FROM_U_CALLBACK_SUBSTITUTE(
    context: *const c_void,
    fromuargs: *mut UConverterFromUnicodeArgs,
    codeunits: *const u16,
    length: i32,
    codepoint: i32,
    reason: UConverterCallbackReason,
    err: *mut UErrorCode,
)