Re: windows, threads and sockets

[Sylvain Le Gall <sylvain@le-gall.net>]

Hello,

On 07-08-2009, Christoph Bauer <christoph.bauer@lmsintl.com> wrote:
>
>> Do you mean that the following code is wrong with 3.11.1 and 
>> not 3.10.2:
>> 
>> let res_listener = Unix.select listOfSockets [] [] timeout in 
>> (List.nth res_listener 0) = listenSocket
>> 
>> Can you find listenSocket in the result elsewhere ?
>
> No! I try to clarify: 
>
> my check is then 
>
>   match Unix.select sockets [] [] timeout with
>      | (l,_,_) ->
>           List.iter (fun sock -> printf "%b,%b\n" (List.mem sock
> sockets) (List.memq sock sockets)) l
>
> I only use OCaml 3.11.0. It only happens on windows.
>
> If I compile and link with -thread and link with ocamlfind ... -package
> threads
> then the result is
>
>   false,false
>
> But without the thread package the result is
>
>   true,true
>

Maybe, I understand the bug. I use "lpOrig = (void *)fd;" where fd is an
OCaml value (in select.c). Without thread and during the
enter/leave_blocking_section(), there is less chance to trigger the GC
and to modify "fd" value. This is the reason why it seems correct
without thread and fall into a bug with thread.

The obvious solution is to replace "lpOrig = (void *)fd" by a non-OCaml
value (e.g. EMode + nth in ocaml list).

Could you reduce your bug to the smallest possible program and submit
the bug on OCaml bug tracking ? 

>
> BTW, I use systhreads, but the files (scheduler.c, unix.ml) I mentioned
> before are used in the vmthread case.
> In otherlibs\systhreads\threadUnix.ml I found
>
> let select = Unix.select
>

This remains another bug (less important) since we cannot use
-vmthreads, Unix.select and pipes on windows. 

Regards,
Sylvain Le Gall