if cap(buf) < len(buf)+20 {
		b := make([]byte, len(buf), 20+cap(buf)*2)
		copy(b, buf)
		buf = b
	}
	writeAt := len(buf)
	buf = buf[0 : len(buf)+ctxt.Arch.PtrSize]
	writePtr(ctxt, buf[writeAt:], word)
	return buf
}

// Write a pointer-sized uint to the beginning of buf.
func writePtr(ctxt *obj.Link, buf []byte, word uint64) {