pub type X509V3_EXT_I2S = Option<unsafe extern "C" fn(method: *const X509V3_EXT_METHOD, ext: *mut c_void) -> *mut c_char>;
enum X509V3_EXT_I2S { None, Some(unsafe extern "C" fn(*const v3_ext_method, *mut c_void) -> *mut i8), }
No value.
Some value of type T.
T