@rbonichon I noticed earlier this week that PR#615 has introduced a closure allocation every time a formatter's queue is flushed (because of the new clear_tag_stack function). This seems gratuitous but I'm not sure if it should be fixed for 4.06.

Cherry-picked in 4.06 : af8f9e8.

@mshinwell
Do you mean that in

let clear_tag_stack state =
  List.iter
    (fun _ -> pp_close_tag state ())
    state.pp_tag_stack

the (fun _ -> pp_close_tag state ()) is gratuitous ?

The type of _ here is actually string. The clear_tag_stack function was actually added to fix the tag closing behavior on flushes --- which was buggy.