Problem: My Perl application has signal handlers installed, which logs (if possible) the signal received, and reacts accordingly. Recently I found one case in our logs showing that a SIGHUP was delivered. The application is running using ActiveState Perl 5.14 on (64bit-)Windows 7. I wonder which event might possibly cause the SIGHUP handler being called (aside from the obvious possibility that my application is doing suicide using this signal).

I am aware that on Windows, signal handling is simulated by turning Windows messages are turned into signals. Looking at the source code of Perl, I found indeed 1 case where SIGHUP seems to be generated. I don't understand much about the Windows API, but the code says:

BOOL WINAPI
win32_ctrlhandler(DWORD dwCtrlType)
...
    switch(dwCtrlType) {
    case CTRL_CLOSE_EVENT:
     /*  A signal that the system sends to all processes attached to a
+ console when
         the user closes the console (either by choosing the Close com
+mand from the
         console window's System menu, or by choosing the End Task com
+mand from the
         Task List
      */
        if (do_raise(aTHX_ 1))        /* SIGHUP */
            sig_terminate(aTHX_ 1);
        return TRUE;
[download]

I roughly (and maybe uncorrectly) understand the comment in that closing the console corresponds to SIGHUP. Trying to verify this, I wrote the following small program:

use strict;
use warnings;
use Config;

BEGIN { 
    open(LOG,">","what_happens.log") or die "$!"; 
    my $ofh = select LOG;
    $|=1;
    select $ofh;
    print LOG "Unbuffered Log\n";
}

sub pout {
    print {$_} @_,"\n" for (*LOG, *STDERR);
}

END { pout("end handler called"); close LOG; }

pout "Started";

my $signum = 0;
foreach my $signame (split(' ', $Config{sig_name})) {
            if ($signum) {
                pout("Establishing $signame $signum");
                $SIG{$signame} = $signame =~ /^KILL|STOP$/
                    ? 'IGNORE'    # According to perldoc perlipc, they
+ can be ignored, but not trapped
                    : sub {
                        $SIG{$signame} = 'DEFAULT';                   
+     
                        pout("Murdered by signal $signame, default han
+dler established");
                        if ($signame eq 'INT') {
                            pout("This seems to be Keyboard interrupt"
+);
                            exit;
                        } else {
                            pout("Suicide");
                            kill($signum, $$);    # proceed with norma
+l handling of signal
                        }
                    };
            }
            ++$signum;
}

pout("Interrupt handlers registered");
sleep(6);
pout("Normal exit");
[download]

For example, if I start the program in a console, and type Control-C while the application is sleeping, I see message This seems to be Keyboard interrupt in my logfile. However, if I close instead the console window, the last message in the log is Interrupt handlers registered. I conclude that closing the window, is invoking either SIGKILL or SIGSTOP - different from what I expected.

I guess that I misunderstood the meaning of SIGHUP on Windows. Could someone help me here?

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