Distributed Systems Network Management (DSNM) Subsystem Interface Development Guide

_ISNULL
A-64
109759—Distributed Systems Network Management (DSNM) Subsystem Interface
Development Guide
DSNM Library Services
_ISNULL
_ISNULL is a Boolean define statement that is TRUE if address is a null extended
memory pointer. TRUE is nonzero, not necessarily -1.
Always use either _ISNULL or _NOTNULL to test a pointer rather than comparing it to
the library literal _NULL. (There are multiple internal values that are accepted as
equivalent to _NULL.)
address input
INT(32):value
is the extended address being tested.
Example
Suppose command^context^def describing the command context area contains the
following:
INT. EXT next^in^lm (input^lm^def);
The following example removes objects from the input list until the list is empty:
INT .EXT cx (command^context^def) = _THREAD^CONTEXT^ADDRESS;
.
.
.
IF _ISNULL (@cx.next^in^lm := _GET^LM (cx._INPUT.OBJECTLIST))
THEN ... < out of input objects > ;
See the _FOBJECT^INIT description for another _ISNULL example.
_ISNULL ( address )