4.13 POINTER Statement

POINTER (pointer,pointee) [,(pointer,pointee)] . . .

• Two pointers can have the same value, so pointer aliasing is allowed.

• When used directly, a pointer is treated like an integer variable. On VAX processors, a pointer occupies one numeric storage unit, so it is a 32-bit quantity (INTEGER*4). On Alpha processors, a pointer occupies two numeric storage units, so it is a 64-bit quantity (INTEGER*8).

• A pointer cannot be a pointee.

• A pointer cannot appear in the following statements:

  ASSIGN	INTRINSIC
  EXTERNAL	PARAMETER

  A pointer can appear in a DATA statement with integer literals only.

• Integers can be converted to pointers, so you can point to absolute memory locations.

• A pointer variable cannot be declared to have any other data type.

• A pointer cannot be a function return value.

• You can give values to pointers by using the %LOC built-in function to retrieve addresses, or by using malloc(3f) on Tru64 UNIX systems to allocate storage for an object. For example:

  
  Using %LOC:                     Using malloc:
  
  INTEGER I(10)                   INTEGER I(10)
  INTEGER I1 (10) /10*10/         POINTER (P,I)
  POINTER (P,I)                   P = MALLOC (40)
  P = %LOC (I1)                   I(2) = I(2) + 1
  I(2) = I(2) + 1
  

• The value in a pointer is used as the pointee's base address.

• A pointee is not allocated any storage. References to a pointee look to the current contents of its associated pointer to find the pointee's base address.

• A pointee cannot be data-initialized or have a record structure that contains data-initialized fields.

• A pointee can appear in only one POINTER statement.

• A pointee array can have fixed, adjustable, or assumed dimensions.

• A pointee cannot appear in the following statements:

  AUTOMATIC	NAMELIST
  COMMON	PARAMETER
  DATA	SAVE
  EQUIVALENCE	STATIC

• A pointee cannot be a dummy argument.

• A pointee cannot be a function return value.

• A pointee cannot be a record field or an array element.