pub type PFNGLUNIFORM3IVARBPROC = Option<unsafe extern "C" fn(location: GLint, count: GLsizei, value: *const GLint)>;
enum PFNGLUNIFORM3IVARBPROC { None, Some(unsafe extern "C" fn(_: i32, _: i32, _: *const i32)), }
No value.
Some value of type T.
T