absolute pointer

[FSAC]

     We are running HP-UP UNIX on a Hewlett-Packard System 9050. THe
HP-UP is SYSV look alike with shared memory operations.  I am trying to
compile a program that allows users to talk with each other.  This
program is similiar to talk except that is uses shared memory.  It
compiles and works under a AT&T SYS5 release 2.  However when I compile
it under hp-UNIX I get the following error messages:

rap.c, line 310: warning: absolute pointer used
rap.c, line 369: warning: absolute pointer used

Lines 310 & 369 are the exact same and look like this:

		if ( shmaddr EQ (char *) -1 ) {


   Can anyone shed some light on what is meant by an absolute
pointer.  I am assuming it doesn't like the cast but I am not sure.
Incidently the "EQ" is defined as "==".


Dennis