Debugger API, compatibility between R7 and R8

[Luke Gorrie]

Hello everybody,

I'm working on a new debugger front-end, and I'm having a problem
with compatibility between R7 and R8.

I'm using int:attached(Pid) to attach myself to an interpreted process
and get the pid for its "meta process" that I send commands to. On R8
this function returns {ok, MetaPid} (fine for me), but on R7 it just
returns 'true'. Maybe this approach is unnecessarily low-level.

Does anyone know a way to do the job that's compatible with both
releases?

Here's the process I'm trying to compatible'ify (offending line starts
with "=>"):

  %% Attach the client process Emacs to the interpreted process Pid.
  %%
  %% spawn_link's a new process to proxy messages between Emacs and
  %% Pid's meta-process.
  debug_attach(Emacs, Pid) ->
      spawn_link(?MODULE, debug_attach_init, [Emacs, Pid]).

  debug_attach_init(Emacs, Pid) ->
      link(Emacs),
=>    case int:attached(Pid) of 
          {ok, Meta} ->
              debug_attach_loop(Emacs, Meta);
          error ->
              exit({error, {unable_to_attach, Pid}})
      end.

  debug_attach_loop(Emacs, Meta) ->
      receive
          {Meta, Msg} ->
              Emacs ! {meta, Msg};
          {emacs, meta, Cmd} ->
              int:meta(Meta, Cmd)
      end,
      debug_attach_loop(Emacs, Meta).

What a pain to be compatible with [{A,B} || A <- [emacs20, emacs21, xemacs],
                                            B <- [r7, r8]] :-)

Cheers,
Luke (trying not to think about "C <- [win32, ...]")