pub type PFNGLGETPROGRAMSTRINGNVPROC = Option<unsafe extern "C" fn(id: GLuint, pname: GLenum, program: *mut GLubyte)>;
enum PFNGLGETPROGRAMSTRINGNVPROC { None, Some(unsafe extern "C" fn(_: u32, _: u32, _: *mut u8)), }
No value.
Some value of type T.
T