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Message-ID: <51433085.8090405@gmail.com>
Date: Fri, 15 Mar 2013 14:30:29 +0000
From: Matej Kosik <5764c029b688c1c0d24a2e97cd764f@gmail.com>
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To: caml-list@inria.fr
CC: Matej Kosik <5764c029b688c1c0d24a2e97cd764f@gmail.com>
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 boundary="------------020204000805000209070309"
Subject: [Caml-list] signal-unsafety of %!

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--------------020204000805000209070309
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit

Hi,

When I compile the attached program

  (with compilers available directly from Debian's repositories)

I can observe a (non-deterministic) deadlock.

When I remove

	%!

from the printf function inside the SIGALRM's handler, the deadlock never seem to occur.

Obviously, interference can be easily introduced in concurrent programs; I was just surprised that even something like

	%!

can cause it.

Isn't this something, that could be avoided in this case?

--------------020204000805000209070309
Content-Type: text/plain;
 name="main.ml"
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename="main.ml"

open Unix

;;

Sys.set_signal Sys.sigalrm
               (Sys.Signal_handle (fun _ -> Printf.printf "H%!"));
ignore (Unix.alarm 1);
while true do
  Printf.printf ".%!"
done

--------------020204000805000209070309
Content-Type: text/plain;
 name="Makefile"
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename="Makefile"

main : % : %.ml
	ocamlfind c -linkpkg -package unix $< -o $@

clean :
	rm -f *.cmo *.cmi main

--------------020204000805000209070309--