fork and open3 on Win32

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

In the below perl script, I fork, then have the child start "cat" via open3(). The child does some I/O with the "cat" process, then exits. I'm using Cygwin's cat.exe .

my $CMD = 'cat';
use IO::Handle;
use IPC::Open3 qw( open3 );
use strict;

my $pid = fork();
if ( !defined($pid) ) {
    die( "$$: Fork failed: $!\n" );
}

# parent
if ( $pid ) {
    print( "$$ FORKED $pid\n" );
}

# child
else {
    my( $pw, $pr, $pe, $pipe );
    foreach $pipe ( $pw, $pr, $pe ) { $pipe = new IO::Handle; }
    my $pipe_pid = open3( $pw, $pr, $pe, $CMD )
        or die( "$$: failed to handle to $CMD: $!\n" );
    print( "$$:\tpipe pid = $pipe_pid\n");

    $pw->print( "hostinfo\n" );
    $pw->print( "quit\n" );
    print( "$$: out: ", $pr->getline(), "\n" );
    exit(0);
}

waitpid( $pid, 0 );
print( "$$ caught $pid: $?\n" );
print( "PARENT $$ exiting\n" );
[download]

This works fine on Unix (perl 5.6.0):

  $ ./t_iohand2
  8629 FORKED 8630
  8630:   pipe pid = 8631
  8630: out: hostinfo

  8629 caught 8630: 0
  PARENT 8629 exiting

However, it does this on Win32 (ActiveState Perl 5.6.0-623 and 5.6.1-625):

D:>perl -w t_iohand2 304 FORKED -1392 am I in cat?

am I in cat?

Use of uninitialized value in print at t_iohand2 line 35. -1392: pipe pid = 1400 -1392: out: 304 caught -1392: 0 PARENT 304 exiting

The process tree for the Win32 output looks like this: 304 -(fork)-> -1392 -(open3)-> 1400

It looks like the STDIN/STDOUT of process 1400 (the open3() child) is getting mixed up with the STDIN/STDOUT of it's parent, -1392.

I'm using "cat" as an example here. In the actual script, $CMD is the path to a shell-like program (similar to csh) running on Win32.

This works fine on Cygwin perl 5.6.1-1, but my project wants to use ActiveState for a variety of reasons.

Thanks for any input!

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