Procedure pointers are used to point to procedures or functions. A procedure
pointer points to an entry point that is bound into the program. Procedure
pointers are defined on the definition specification.
The length of the procedure pointer field must be 16 bytes long and must
be aligned on a 16 byte boundary. This requirement for boundary alignment
can cause a pointer subfield of a data structure not to follow the preceding
field directly, and can cause multiple occurrence data structures to have
non-contiguous occurrences. For more information on the alignment of subfields,
see Aligning Data Structure Subfields.
The default initialization value for procedure pointers is *NULL.
Examples
Figure 102. Defining pointers
*.. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 ...+... 8
DName+++++++++++ETDsFrom+++To/L+++IDc.Keywords+++++++++++++++++++++++++++++
*
* Define a basing pointer field and initialize to the address of the
* data structure My_Struct.
*
D My_Struct DS
D My_array 10 DIM(50)
D
D Ptr1 S 16* INZ(%ADDR(My_Struct))
*
* Or equivalently, defaults to length 16 if length not defined
*
D Ptr1 S * INZ(%ADDR(My_Struct))
*
* Define a procedure pointer field and initialize to NULL
*
D Ptr1 S 16* PROCPTR INZ(*NULL)
*
* Define a procedure pointer field and initialize to the address
* of the procedure My_Proc.
*
D Ptr1 S 16* PROCPTR INZ(%PADDR(My_Proc))
*
* Define pointers in a multiple occurrence data structure and map out
* the storage.
*
DDataS DS OCCURS(2)
D ptr1 *
D ptr2 *
D Switch 1A
