From: Xavier Leroy <xavier.leroy@inria.fr>
To: Yoann Padioleau <Yoann.Padioleau@irisa.fr>
Cc: caml-list@inria.fr
Subject: Re: [Caml-list] replay debugger
Date: Thu, 4 Oct 2001 14:39:09 +0200 [thread overview]
Message-ID: <20011004143909.A16053@pauillac.inria.fr> (raw)
In-Reply-To: <wi6pu86nd2j.fsf@kochab.irisa.fr>; from Yoann.Padioleau@irisa.fr on Tue, Oct 02, 2001 at 07:53:24PM +0200
[The question was: how does the OCaml debugger implements reverse execution?]
> Y'a t'il de la doc sur le fonctionnement interne du debuggger.
> Comment ca marche ? comment ki fait pour revenir en arriere ?
Like all "time-travel" debuggers: by periodic checkpointing. That is,
it saves the state of the program from time to time, and uses these
checkpoints to restore the state of the program at any time. E.g.
say you stop the program and wish to execute it backwards one step.
Find the most recent checkpoint, which was taken N steps ago;
duplicate it, and run one copy N-1 steps forward.
We learnt this trick from Andrew Tolmach's thesis:
http://www.cs.pdx.edu/~apt/thesis.ps.Z
The only difference between Tolmach's system and ocamldebug is that
the former uses first-class continuations to capture the checkpoints,
while ocamldebug uses the fork() Unix system call. Thus, each
checkpoint is really a separate process, and all of them communicate
with the debugger via sockets.
- Xavier Leroy
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next prev parent reply other threads:[~2001-10-04 12:39 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-10-02 17:53 Yoann Padioleau
2001-10-04 12:39 ` Xavier Leroy [this message]
2001-11-26 14:51 ` Fergus Henderson
2001-11-26 16:14 ` Xavier Leroy
2001-11-26 18:40 ` [Caml-list] Beware of compare (and Ocaml beaten by Java) Mattias Waldau
2001-11-27 9:21 ` Xavier Leroy
2001-11-27 9:41 ` Mattias Waldau
2001-11-30 9:12 ` Pierre Weis
2001-12-03 21:37 ` Chris Hecker
2001-11-27 17:03 ` [Caml-list] bytegen.comp_expr error when doing object copying Neil Inala
2001-11-28 20:15 ` Xavier Leroy
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