pub type PFNGLVERTEXATTRIBS3FVNVPROC = Option<unsafe extern "C" fn(index: GLuint, n: GLsizei, v: *const GLfloat)>;
enum PFNGLVERTEXATTRIBS3FVNVPROC { None, Some(unsafe extern "C" fn(_: u32, _: i32, _: *const f32)), }
No value.
Some value of type T.
T