POINTER - Integer

Intel® Fortran Compiler Classic and Intel® Fortran Compiler Developer Guide and Reference

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ID 767251

Date 3/22/2024

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POINTER - Integer

Statement: Establishes pairs of objects and pointers, in which each pointer contains the address of its paired object. This statement is different from the Fortran POINTER statement.

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

pointer	Is a variable whose value is used as the address of the `pointee`.
pointee	Is a variable; it can be an array name or array specification. It can also be a procedure named in an EXTERNAL statement or in a specific (non-generic) procedure interface block.

The following are pointer rules and behavior:

Two pointers can have the same value, so pointer aliasing is allowed.
When used directly, a pointer is treated like an integer variable. On IA-32 architecture, a pointer occupies one numeric storage unit, so it is a 32-bit quantity (INTEGER(4)). On Intel® 64 architecture, 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 an ASSIGN statement and cannot have the following attributes:

ALLOCATABLE	INTRINSIC	POINTER
EXTERNAL	PARAMETER	TARGET

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 doing the following:

Retrieve addresses by using the LOC intrinsic function (or the %LOC built-in function).
Allocate storage for an object by using the MALLOC intrinsic function (or by using malloc(3f) on Linux* systems).

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 = 10
I(2) = I(2) + 1              I(2) = I(2) + 1

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

The following are pointee rules and behavior:

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 integer POINTER statement.
A pointee array can have fixed, adjustable, or assumed dimensions.

A pointee cannot appear in a COMMON, DATA, EQUIVALENCE, or NAMELIST statement, and it cannot have the following attributes:

ALLOCATABLE	OPTIONAL	SAVE
AUTOMATIC	PARAMETER	STATIC
INTENT	POINTER

A pointee cannot be:
- A dummy argument
- A function return value
- A record field or an array element
- Zero-sized
- An automatic object
- The name of a generic interface block
If a pointee is of derived type, it must be of sequence type.

Example

 POINTER (p, k)
 INTEGER j(2)

 ! This has the same effect as j(1) = 0, j(2) = 5
 p = LOC(j)
 k = 0
 p = p + SIZEOF(k) ! 4 for 4-byte integer
 k = 5

Parent topic: O to P

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Intel® Fortran Compiler Classic and Intel® Fortran Compiler Developer Guide and Reference

POINTER - Integer

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