SIGALRM and Win32

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

What is the status on alarm(), along with $SIG{ALRM} with Win32? I am working on a Windows XP system and cannot get the alarm signal to work, yet I am also not getting errors of alarm() not being implemented. Does anyone have any useful information to share with me about this issue? For the record, I understand the obvious fact that "you can't use alarm on Windows" here, I'm just looking for information on why that is and if it is being worked on as we speak :)

C:\>perl -v

This is perl, v5.8.2 built for MSWin32-x86-multi-thread
(with 25 registered patches, see perl -V for more de

Copyright 1987-2003, Larry Wall

Binary build 808 based on sources provided by
   ActiveState Corp. http://www.ActiveState.com
ActiveState is a division of Sophos.
Built Dec 31 2003 09:46:50
[download]

Comment on SIGALRM and Win32 Download Code

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Re: SIGALRM and Win32 by Anonymous Monk on Mar 17, 2004 at 09:15 UTC
What is your code? It works on 5.8.x `eval { local $SIG{ALRM} = sub { die "alarm\n" }; # NB: \n required alarm 2; # $nread = sysread SOCKET, $buffer, $size; sleep 4; alarm 0; }; if ($@) { die unless $@ eq "alarm\n"; # propagate unexpected errors # timed out warn "alarm timed out"; } else { warn "success "; } __END__ alarm timed out at - line 11.` [download]	[reply] [d/l]
Re^2: SIGALRM and Win32 by Anonymous Monk on Mar 17, 2004 at 09:27 UTC
I think it's because you are intermixing sleep and alarm. Some platforms implement alarm using sleep (or something like that - some tidbit of info I picked up somewhere), so mixing those two together is not good. If you replace your `sleep 4;` line with `select(undef,undef,undef,4);` or `my $foo = <STDIN>;`, it will not work -- you get a success with the select() version and the script 'hangs' waiting for input with the STDIN version (on my system anyhow). Just as if the signal was never received.	[reply] [d/l] [select]