pub type PFNGLGETPROGRAMSTRINGARBPROC = Option<unsafe extern "C" fn(target: GLenum, pname: GLenum, string: *mut c_void)>;
enum PFNGLGETPROGRAMSTRINGARBPROC { None, Some(unsafe extern "C" fn(_: u32, _: u32, _: *mut c_void)), }
No value.
Some value of type T.
T