request_reply.xml

<!-- based on xproto -->
<xcb header="request_reply">

  <struct name="STR">
    <field type="CARD8" name="name_len" />
    <list type="char" name="name">
      <fieldref>name_len</fieldref>
    </list>
  </struct>

  <request name="ListExtensions" opcode="99">
    <reply>
      <field type="CARD8" name="names_len" />
      <pad bytes="24" />
      <list type="STR" name="names">
        <fieldref>names_len</fieldref>
      </list>
    </reply>
  </request>

</xcb>