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Date: Wed, 19 Mar 2014 22:21:34 +0100
From: Anders Peter Fugmann <anders@fugmann.net>
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Subject: [Caml-list] Bug when printing from signal handlers?

Hi,

I'm experiencing a live lock while printing from a signal handler.
It seems to be triggered when the main is interrupted while printing.

The following program exposes the problem:
(tested on 4.00.1 and 4.01.0)

let rec loop () =
   print_endline "In main thread";
   loop ()

let _ =
   Sys.(set_signal sigalrm
          (Signal_handle
             (fun _ -> print_endline "In signal handler")));
   let _ = Unix.(setitimer ITIMER_REAL
                   { it_interval = 0.1; it_value = 0.1 })
   in
   loop ()

For some reason, in caml_flush_parial channel->buff becomes greater than 
channel->curr which means caml_flush never completes, as 
caml_flush_partial never returns true.

Is printing from a signal handler illegal?
I tries searching for bug on this matter but only found examples that 
printed from signal handlers.

Regards
Anders