make problem: SMlib.h

[Paul Hepworth <phepworth s-vision com>]

Here are the error messages (making gnome-core from cvs):

Making all in gsm
make[2]: Entering directory `/home/pjh/gnome/gnome-core/gsm'
Computing dependencies for testbed.c...
In file included from testbed.c:8:
manager.h:7: X11/SM/SMlib.h: No such file or directory
make[2]: *** [.deps/testbed.P] Error 1
make[2]: Leaving directory `/home/pjh/gnome/gnome-core/gsm'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/home/pjh/gnome/gnome-core'
make: *** [all-recursive-am] Error 2

What is SMlib?  (Session Management?)  Do I really need it?  From where
do I get it?
Thanks much.


Paul