pub type PFNGLCLEARBUFFERUIVPROC = Option<unsafe extern "C" fn(buffer: GLenum, drawBuffer: GLint, value: *const GLuint)>;
enum PFNGLCLEARBUFFERUIVPROC { None, Some(unsafe extern "C" fn(_: u32, _: i32, _: *const u32)), }
No value.
Some value of type T.
T