pub type PFNGLGETUNIFORMI64VARBPROC = Option<unsafe extern "C" fn(program: GLuint, location: GLint, params: *mut GLint64)>;
enum PFNGLGETUNIFORMI64VARBPROC { None, Some(unsafe extern "C" fn(_: u32, _: i32, _: *mut i64)), }
No value.
Some value of type T.
T