problem with dup() in mod-perl?

[Erik Rantapaa]

Is anyone aware of a problem with dup-ing a fd to stdin?
Attached is a module I'm using to get the output of an exec-ed command.

When I call this module from a script it gives the right output.
When I call this from a Mason module, I get "0 0 0" (as if no input was read).
When I call this from the single threaded server (using -X), the request
hangs, and it seems to be taking input from my shell (the shell that
invoked 'httpd -X').

If I run strace on httpd, instead of a "dup2(X, 0)" call, I see a single
argument call "dup(X)"; the dup to stdout is a dup2() call.

It seems that someone is intercepting the dup2(X, 0) call and treating it
as a single argument dup() call.

My platform:

Apache: 1.3.22
mod_perl: 1.26
Linux: Redhat 7.2/Intel


use strict;
use FileHandle;
package Test;
 
sub test {
        my ($R, $W) = open_proc([ "/usr/bin/wc" ]);
        print $W "this is a test\n";
        close($W);
        my $buf;
        while (<$R>) {
                $buf .= $_;
        }
        close($R);
        $buf;
}
 
sub open_proc {
        my $args = shift;
        my ($R1, $W1, $R2, $W2);
        ($R1, $W1) = FileHandle::pipe
                or die "unable to create pipes";
        ($R2, $W2) = FileHandle::pipe
                or die "unable to create pipes";
        my $pid;
        unless (defined($pid = fork)) {
                die "unable to fork: $!";
        } elsif ($pid == 0) { # child
                time;
                open(STDIN, "<&".fileno($R1))
                        or die "unable to dup STDIN: $!";
                time;
                open(STDOUT, ">&".fileno($W2))
                        or die "unable to dup STDOUT: $!";
                close($W1);
                close($R2);
                exec(@$args)
                        or die "unable to exec ".$args->[0].": $!";
        }
        ($R2, $W1, $pid);
}