[ns] compiling error on red hat 7

[Milind Dilip Kopikare <kopi@stanford.edu>]

Hi Everyone,
 I recently upgraded to red hat 7. when i tried to reinstall ns, it gave
me this error that the abort() function in the /tclcl-1.0b9/tracedvar.cc
is undeclared! This wasnt happenning when I had originally installed the
ns on redhat 6.1. here's the error:
==================
  tracedvar.cc: In method `char *TracedInt::value (char *, int)':
tracedvar.cc:102: `abort' undeclared (first use this function)
tracedvar.cc:102: (Each undeclared identifier is reported only once for
each function it appears in.)
make: *** [tracedvar.o] Error 1
tclcl-1.0b9 make failed! Exiting ...
=====================

could someone guide me as to what could be wrong?

Thanks,
Milind