Re: [Caml-list] Cash broken?

[John Goerzen <jgoerzen@complete.org>]

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On Fri, May 28, 2004 at 12:26:15PM +0200, Bruno.Verlyck@inria.fr wrote:
>     # open Cash;;
>     # run_with_strings (fun () -> exec_path "ls" []);;
>     Exception: Sys_error "Bad file descriptor".
>     # Exception: Sys_error "Bad file descriptor".
>    I can't make any of the run_with_* that I've tried work, whether in
>    my programs or with cashtop.
> 
>    Ideas?  (Cash 0.20)
> Not a lot with so little info (of course it works here).  Would you
> mind sending me more OS details ?  A backtrace would be very useful,
> and/or the result of trace/truss/strace -f ?

This is on Debian sid, Linux 2.6.6.  I couldn't figure out how to get a
backtrace.  However, from the forked child, I see:

[pid  9461] close(4)                    = 0
[pid  9461] close(4)                    = -1 EBADF (Bad file descriptor)

(Full strace attached)

Will try the patch.  How does the CVS version rank in terms of
stability?

> That said, what comes to mind is that the behavior of close_{in,out}
> has changed in Pervasives over the last versions of Caml.  I wrote
> some (too many) lines of code to make Cash.close_{in,out} work anyway.
> I see in the CVS log that there was a change related to that, some
> time after 3.07 (see the attached patch).  You could try it, or even
> try the entire CVS version of Cash.
> 
> Bruno.

> Index: io_3_2.ml
> ===================================================================
> RCS file: /net/pauillac/caml/repository/cash/io_3_2.ml,v
> retrieving revision 1.47
> retrieving revision 1.48
> diff -c -a -r1.47 -r1.48
> *** io_3_2.ml	2002/08/05 17:07:37	1.47
> --- io_3_2.ml	2002/12/05 17:37:52	1.48
> ***************
> *** 116,126 ****
>         Some fd ->
>           let res = low_close_fd fd in  (* low_close_fd will tell it. *)
>           do {
> !           close_any any_chan; (* Never raise exception in the current implementation. *)
>             res
>           } ]
>     in
>     (fun ichan -> close (anychan_of_ichan ichan),
>      fun ochan -> do { flush ochan; close (anychan_of_ochan ochan) })
>   ;
>   
> --- 116,129 ----
>         Some fd ->
>           let res = low_close_fd fd in  (* low_close_fd will tell it. *)
>           do {
> !           (* Used to raise no exception, but this varies between implementations... *)
> !           try close_any any_chan with [ Sys_error "Bad file descriptor" -> () ];
>             res
>           } ]
>     in
>     (fun ichan -> close (anychan_of_ichan ichan),
> +    (* Current religion says: flush do nothing on a closed channel. *)
> +    (* Current implication is: if an unflushed channel's fd is closed, it's an error. *)
>      fun ochan -> do { flush ochan; close (anychan_of_ochan ochan) })
>   ;

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