"_thread_sys__exit": debugging clue req'd

["Bruce M. Walker" <bmw_(_at_)_borderware_(_dot_)_com>]

[Gee whiz, I went off and did non-developer stuff for a few years
and they changed everything on me! ;-) ]

I'm trying to debug why pppoe (usr.sbin version) dies under load
for me.  Summary: I am launching it from ppp using an appropriate

  set device "!/usr/sbin/pppoe -i fxp0"

line, and it works for light network activity, but if I copy a 100K
file in either direction, pppoe exits causing ppp to recycle the
connection.

Anyway, when I connect to the running pppoe process with gdb and
break on _exit, all I ever get for a stack trace is

  _thread_sys__exit
  _exit

Argh!  I wanna see where it came from!  I tried linking the whole
thing -static: no help.  I now see that there appears to be two
libc's: ordinary libc and "reentrant" libc_r where presumably
everything is thread-safe.

But I just want a normal old-fashioned non-threaded version of the
code so I can get a straight-forward stack trace.  Is that too much
to ask?  :-)

Can anyone enlighten an old war-horse on "how it's done now"?

Thanks!

-bmw