Sys::Signal Weirdness

[Bill Moseley]

This is slightly off topic, but my guess is Sys::Signal is mostly used by
mod_perl people.  Can someone else test this on their machine?

I have this weird problem where I'm not catching $SIG{ALRM}.  The test code
below is a simple alarm handler that looks like this:

    eval {
        local $SIG{__DIE__};
        if ( $timeout  ) {
            my $h = Sys::Signal->set(
                ALRM => sub { die "Timeout after $timeout seconds\n" }
            );
            warn "Set Signal $h\n";
            alarm $timeout;
        }
        print "Test 1 Parent reading: $_" while <FH>;

        alarm 0 if $timeout;
    };

This isn't working -- but if I simply comment out the if ( $timeout ) block
it works. 

Here's the output on my machine.

>perl test.pl

Starting test2 - WITHOUT 'if ( $timeout )'
Set Signal Sys::Signal=SCALAR(0x810d120)
in child loop 12423
Test 2 Parent reading: 1
Test 2 Parent reading: 2
Test 2 Parent reading: 3
Timeout after 4 seconds  <<<<--- good!

Starting test1 - with 'if ( $timeout )'
Set Signal Sys::Signal=SCALAR(0x810d12c)
in child loop 12424
Test 1 Parent reading: 1
Test 1 Parent reading: 2
Test 1 Parent reading: 3
Alarm clock         <<<<<--- huh?

Here's some cut-n-paste test code.  This is what I get on Linux under 5.6.

#!/usr/local/bin/perl -w
use strict;

test2();
test1();

$|= 1;

use Sys::Signal;

sub test1 {
    warn "\nStarting test1 - with 'if ( \$timeout )'\n";


   my $child = open( FH, '-|' );
   die unless defined $child;

   loop() unless $child;  # not that this works

    my $timeout = 4;

    eval {
        local $SIG{__DIE__};
        if ( $timeout  ) {
            my $h = Sys::Signal->set(
                ALRM => sub { die "Timeout after $timeout seconds\n" }
            );
            warn "Set Signal $h\n";
            alarm $timeout;
        }
        print "Test 1 Parent reading: $_" while <FH>;

        alarm 0 if $timeout;
    };


    if ( $@ ) {
       warn $@;
       kill( 'HUP', $child );
    }
}

sub test2 {
    warn "\nStarting test2 - WITHOUT 'if ( \$timeout )'\n";


   my $child = open( FH, '-|' );
   die unless defined $child;

   loop() unless $child;

    my $timeout = 4;

    eval {
        local $SIG{__DIE__};
   ###     if ( $timeout  ) {
            my $h = Sys::Signal->set(
                ALRM => sub { die "Timeout after $timeout seconds\n" }
            );
            warn "Set Signal $h\n";
            alarm $timeout;
   ###     }
        print "Test 2 Parent reading: $_" while <FH>;

        alarm 0 if $timeout;
    };


    if ( $@ ) {
       warn $@;
       kill( 'HUP', $child );
    }
}


sub loop {
    $|=1;
    my $x;
    warn "in child loop $$\n";
    sleep 1, ++$x, print "$x\n"  while 1;
}


Bill Moseley
mailto:[EMAIL PROTECTED]

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