[Caml-list] Size limit on marshalling?

[Caml-list] Size limit on marshalling?

[Yaron M. Minsky]

I've been getting some fairly inexplicable crashes on marshalling and
unmarshalling values, and I'm wondering if anyone has an idea why.  Here's
a code snippet that will crash my copy of ocaml.

First, I create a pointlessly large array, and then save it to disk:

# let save_value fname value =
     let file = open_out_bin fname in
     output_value file value;
     close_out file;;
      val save_value : string -> 'a -> unit = <fun>

# let ar = Array.init (10000 * 256) (fun i -> String.copy "fooobar doobar");;
# save_value "/home/yminsky/foo.val" ar;;

The resulting file is 38400025 bytes long.  Note that the length appears
to be critical.  If you replace "fooobar doobar' with "foobar doobar", the
problem goes away.

At this point, I start a new session of ocaml and reload the value, and
then ensure that it is garbage collected.  That's when I get the segfault.

# let ar = (get_value "foo.val" : string array);;
# let ar = ();;
# Gc.compact ();;

And that's when I get the segfault.  So, any thoughts?  Is this a bug?  Or
just some unspoken limit of the compiler?  This is a dummy example, but
this is a real limit I'm running up against in my code.

Yaron

-- 
|--------/            Yaron M. Minsky              \--------|
|--------\ http://www.cs.cornell.edu/home/yminsky/ /--------|

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Re: [Caml-list] Size limit on marshalling?

[Damien Doligez]

On Wednesday, January 15, 2003, at 10:25 PM, Yaron M. Minsky wrote:

> First, I create a pointlessly large array, and then save it to disk:
[...]
> The resulting file is 38400025 bytes long.  Note that the length 
> appears
> to be critical.
[...]
> # let ar = (get_value "foo.val" : string array);;
> # let ar = ();;
> # Gc.compact ();;

This is a known bug (PR#1495) with compaction and demarshalling
of very large values.  It is already fixed in the development version.

Please contact me if you need a patch.

-- Damien

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