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To: damien.doligez@inria.fr
Cc: caml-list@inria.fr
Subject: Re: [Caml-list] Unix.file_descr -> int ???
In-Reply-To: <200206120953.LAA0000032113@beaune.inria.fr>
References: <200206120953.LAA0000032113@beaune.inria.fr>
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Message-Id: <20020612185729P.garrigue@kurims.kyoto-u.ac.jp>
Date: Wed, 12 Jun 2002 18:57:29 +0900
From: Jacques Garrigue <garrigue@kurims.kyoto-u.ac.jp>
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From: Damien Doligez <damien.doligez@inria.fr>
> >Windows version:
> >
> >let dump_handle (h : Unix.file_descr) =
> >  let obj = Obj.repr h in
> >  if Obj.is_block obj && Obj.tag obj = Obj.custom_tag then
> >    Nativeint.format "%x" (Obj.obj obj)
> >  else invalid_arg "dump_handle"
> 
> This does not work.  You are printing the address of the custom block
> that contains the handle, but this address can change during program
> execution.

Indeed, this is buggy. But you could have given the right answer :-)

let dump_handle (h : Unix.file_descr) =
  let obj = Obj.repr h in
  if Obj.is_block obj && Obj.tag obj = Obj.custom_tag then
    Nativeint.format "%x" (Obj.obj (Obj.field obj 1))
  else invalid_arg "dump_handle"

Jacques Garrigue
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