pub type PFNGLSECONDARYCOLOR3USPROC = Option<unsafe extern "C" fn(red: GLushort, green: GLushort, blue: GLushort)>;
enum PFNGLSECONDARYCOLOR3USPROC { None, Some(unsafe extern "C" fn(_: u16, _: u16, _: u16)), }
No value.
Some value of type T.
T