Function lumen_app_expose_v2 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn lumen_app_expose_v2(
    app: *mut LumenApp,
    name: *const c_char,
    arg_count: u32,
    func: Option<LumenFnV2>,
    user_data: *mut c_void,
) -> LumenStatus

Expose a native callback to the app’s script under name, using the out-parameter callback convention (ABI 0.3).

Identical to lumen_app_expose except func is a LumenFnV2: it receives a *mut LumenValue out-pointer as its first argument and writes its result there instead of returning a LumenValue by value. This lets ctypes / libffi-only bindings register callbacks without hand-encoding the platform’s aggregate-return (sret) convention. Prefer this over lumen_app_expose for non-Rust embedders; v1 is retained for source compatibility.