pub type PFNGLSECONDARYCOLOR3UBPROC = Option<unsafe extern "C" fn(red: GLubyte, green: GLubyte, blue: GLubyte)>;
enum PFNGLSECONDARYCOLOR3UBPROC { None, Some(unsafe extern "C" fn(_: u8, _: u8, _: u8)), }
No value.
Some value of type T.
T