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Date: Mon, 13 Jul 2015 12:20:23 +0900
From: Oleg <oleg@okmij.org>
To: mwh@cs.umd.edu
Cc: caml-list@inria.fr
Message-ID: <20150713032023.GA694@Magus>
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Subject: Re: [Caml-list] Scanning objects outside the OCaml heap


> Does anyone know: Is there any way to make outside memory scannable by the
> GC?

The library of delimited control delimcc

        http://okmij.org/ftp/continuations/caml-shift.tar.gz

in native mode has to perform a custom scan of pieces of memory stored
outside the OCaml heap. Captured delimited continuation is essentially
a portion of stack. Native OCaml uses stack for boxed and unboxed
values. Thus the captured continuation is a curious data structure
that contains both boxed (OCaml) and unboxed (machine) values. Delimcc
stores captured continuation outside the OCaml heap and has to scan
them at GC time.

The file stacks-native.c in caml-shift.tar.gz shows how the
interaction with GC is done. BTW, when installing a new GC call-back,
don't forget the previously installed one.