} else if err != io.ErrNoProgress {
			t.Error("unexpected error:", err)
		}
	case <-time.After(time.Second):
		t.Error("test timed out (endless loop in ReadByte?)")
	}
}

// A StringReader delivers its data one string segment at a time via Read.
type StringReader struct {
	data []string
	step int
}

func (r *StringReader) Read(p []byte) (n int, err error) {
	if r.step < len(r.data) {
		s := r.data[r.step]

		if dt.ByteSize < 0 && tag == "" { // opaque unnamed struct - should not be possible
			break
		}
		if tag == "" {
			tag = anonymousStructTag[dt]
			if tag == "" {
				tag = "__" + strconv.Itoa(tagGen)
				tagGen++
				anonymousStructTag[dt] = tag
			}
		} else if t.C.Empty() {
			t.C.Set(dt.Kind + " " + tag)
		}
		name := c.Ident("_Ctype_" + dt.Kind + "_" + tag)