Powerful ocaml.toplevel.mk about bsdowl HOT 2 CLOSED

Using Toploop.execute_phrase to initialise the toplevel from the
function assigned to Toploop.toplevel_startup_hook does not work, it
seems that the environment is reset when exiting the hook. Here is an
example illustrating this behaviour:

let execute_toplevel_phrase s =
  let phrase =
    !Toploop.parse_toplevel_phrase (Lexing.from_string s)
  in
  if Toploop.execute_phrase true Format.std_formatter phrase then
    ()
  else
    failwith "execute_toplevel_phrase"

let bootstrap () =
  execute_toplevel_phrase "let zero = 0;;"

let _ =
  Toploop.toplevel_startup_hook := bootstrap

While the initialisation routine echoes a val zero : int = 0
message, using zero results in an error indicating that zero is
unbound. But in the toplevel, using the command bootstrap() results
in zero being bound to 0 as expected.

We therefore may choose to rely exclusively on initialisation files to configure the toplevel adequately. We need to initialise correctly the toplevel, wether it is used in without being installed or being installed.

from bsdowl.

The best way to provide this functionality is to prepare a corresponding initialisation file and ensuring it is read at starting time. To ease this, a target display-developer-dirs has been added to the ocaml.toplevel.mk file in 9c85461.

from bsdowl.