I finally realized that the FILE structure is different in pthreads
and that libg++/libstdc++ are poking around in the FILE internals, so
it wasn't going to work. However, I did build a version of libg++/libstdc++
with pg++, and that let the pthreads code use cerr. The basic steps I
took were:

ln -s /usr/include/sys/* /usr/local/pthreads/include/sys/
ln -s /usr/include/* /usr/local/pthreads/include/
make CXX="/usr/local/pthreads/bin/pg++ -I." CC=/usr/local/pthreads/bin/pgcc DESTDIR=/usr/local/pthreads
make CXX="/usr/local/pthreads/bin/pg++ -I." CC=/usr/local/pthreads/bin/pgcc DESTDIR=/usr/local/pthreads install

   The second time around I also had the sense to change LIB=g++ and
LIB=stdc++ to LIB=g++_r and LIB=stdc++_r, respectively, so that I
didn't have to worry about conflicts with the existing libs. BTW, it
seems to work with both static and dynamic linking.
   Thought this might interest some people...

                                      Gary D. Duzan
                         Humble Practitioner of the Computing Arts