Broken su in current - trying to fix myself, help needed!

Hello!

I really not at all good at any kind of system programming
in FreeBSD or Un*x, but since my contacts with last commited
of su could not be establish i decided to look at it myself.

If you don't know what is the problem i'll describe it shortly:

if you try to run a very simple perl script:

#!/usr/bin/perl
$com="/usr/bin/su root -c 'echo heck'";
system($com);
print "done!\n";

it will print 
heck

and then

Suspended (tty output)

and will hang in memory untill you type
fg

then you get

done!


I am working in csh, but i tested it in sh - result is
the same. FreeBSD version is  7-PRERELEASE.


So, I fetched su v. 1.76 from 6.2-STABLE and compiled it - it works
like a charm. SO, i decided to figure what fails in 1.86.

There are such like in the default: dection of switch

                child_pgrp = getpgid(child_pid);
                if (tcgetpgrp(STDERR_FILENO) == child_pgrp)
                        tcsetpgrp(STDERR_FILENO, getpgrp());


The problem is here.
getpgid(child_pid) simply fails with errno 3 (process doesn't exist)
and tcgetpgrp(STDERR_FILENO) return 100000 (can it be THAT high? i though
it is only in 0-65535 range).

The weird thing is that if i just comment out those lines like this

/* child_pgrp = getpgid(child_pid);
   if (tcgetpgrp(STDERR_FILENO) == child_pgrp) */
   tcsetpgrp(STDERR_FILENO, getpgrp());

su starts working again just fine.

Any idea why getpgid fails and why tcgetpgrp return 100000 (always the same
number)? What will brak if i leave these lines commented?

--
Regards,
Artem