infinite loop that cannot be interrupted by Control-C

infinite loop that cannot be interrupted by Control-C

[Eijiro Sumii]

Hi,

It seems that the infinite loop

  let rec x = 1 :: x in x = x ;;

cannot be interrupted by Control-C in the interactive session of
Objective Caml 3.09.0, at least on linux-i386 and solaris-sparc.  Is
this a feature or a bug?

(I did some search and found the same question at

http://caml.inria.fr/pub/ml-archives/caml-list/2005/09/3440c94ff51afc4a5db290c9d811f406.en.html

but there seems to be no answer...)

Thanks,

        Eijiro

Re: [Caml-list] infinite loop that cannot be interrupted by Control-C

[Jonathan Roewen]

> It seems that the infinite loop
>
>  let rec x = 1 :: x in x = x ;;
>
> cannot be interrupted by Control-C in the interactive session of
> Objective Caml 3.09.0

This is probably because of the way the interpreter is designed.

Signals are only checked after function calls, and one other operation
I can't remember off hand. Obviously, in your example, neither of
these cases occur, so ocaml doesn't get a chance to check for any
signals: hence, can't be interrupted.

Jonathan

Re: infinite loop that cannot be interrupted by Control-C

[Eijiro Sumii]

P.S.  For information, the execution _does_ terminate in some older
versions (because = used to check == first) as well as in
non-interactive cases.