pub type PFNGLMULTITEXCOORD3FVARBPROC = Option<unsafe extern "C" fn(target: GLenum, v: *const GLfloat)>;
enum PFNGLMULTITEXCOORD3FVARBPROC { None, Some(unsafe extern "C" fn(_: u32, _: *const f32)), }
No value.
Some value of type T.
T