pub type gcry_handler_no_mem_t = Option<unsafe extern "C" fn(*mut c_void, size_t, c_uint) -> c_int>;
enum gcry_handler_no_mem_t { None, Some(unsafe extern "C" fn(_: *mut c_void, _: usize, _: u32) -> i32), }
No value.
Some value of type T.
T