Re: [Caml-list] Unix file descriptors vs. in/out channels

[David Sheets <sheets@alum.mit.edu>]

On Mon, Aug 18, 2014 at 6:18 PM, Thomas Braibant
<thomas.braibant@gmail.com> wrote:
> Ah, my bad, sorry for the noise!
>
> Le 18 août 2014 18:58, "Xavier Leroy" <Xavier.Leroy@inria.fr> a écrit :
>
>> On 18/08/14 18:52, Thomas Braibant wrote:
>>
>> > Well, I was thinking about the following situation
>> >
>> >   let open Unix in
>> >   let fd = openfile "foo.bar" [O_RDWR; O_TRUNC; O_CREAT] 0o640 in
>> >   let o = out_channel_of_descr fd in
>> >   let i = in_channel_of_descr fd in
>> >   let i2 = in_channel_of_descr fd in
>> >   Printf.printf "1\n%!";
>> >   close_in i;
>> >   Printf.printf "2\n%!";
>> >   close_in i2;
>> >   Printf.printf "3\n%!";
>> >   close_out o;
>> >   Printf.printf "Ok\n%!"
>> >
>> > that raises the fatal error: exception Sys_error("Bad file
>> > descriptor"), and now, I do not understand your remark either :(.
>>
>> I said "close all your channels at once when you're done with the
>> underlying file descriptor".  What you observe is that after the first
>> close_in, all the other channels are unusable, because the underlying
>> FD is closed.

I'm sorry. I still don't understand. The following raises on the first close_in:

let open Unix in
let fd = openfile "foo.bar" [O_RDWR; O_TRUNC; O_CREAT] 0o640 in
let o = out_channel_of_descr fd in
let i = in_channel_of_descr fd in
let i2 = in_channel_of_descr fd in
Printf.printf "1\n%!";
close_out o;
close_in i;
close_in i2;
Printf.printf "Ok\n%!"

To get the error ignoring property, I think you have to use
close_out_noerr (not in this case) and close_in_noerr.

Maybe I've missed some subtlety here, though. I'm a little uneasy
ignoring *all* errors...

David

>> - Xavier Leroy
>>
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