pub type PFNGLSHADEROP2EXTPROC = Option<unsafe extern "C" fn(op: GLenum, res: GLuint, arg1: GLuint, arg2: GLuint)>;
pub enum PFNGLSHADEROP2EXTPROC { None, Some(unsafe extern "C" fn(u32, u32, u32, u32)), }
No value.
Some value of type T.
T