pub type PFNGLSECONDARYCOLOR3UBEXTPROC = Option<unsafe extern "C" fn(red: GLubyte, green: GLubyte, blue: GLubyte)>;
enum PFNGLSECONDARYCOLOR3UBEXTPROC { None, Some(unsafe extern "C" fn(_: u8, _: u8, _: u8)), }
No value.
Some value of type T.
T