Pointer Dereferencing
Syntax Format 1
Syntax Format 2
Syntax Rules Format 1
- The :: syntax allows for multiple operands to be chained together (whereas Format 2 is restricted to one AT clause).
- pointer-1 must be typed unless used with the DATA keyword. If pointer-1 is typed, typedef-name-1 or typedef-component-1 must be the type or sub-typedef component of the pointer type.
- typedef-component-1 can be qualified with :: qualification but not with the OF keyword.
Syntax Rules Format 2
- pointer-2 must be typed if used with the DATA keyword which has no reference modification specified. If pointer-2 is typed, typedef-name-2 or typedef-component-2 must be of the same type or component of the pointer type.
- typedef-component-2 cannot be qualified.
Syntax Rules All Formats
- Use of :: for dereferencing and the AT keyword in the same operand is not allowed.
- Reference modification can only follow directly after the DATA keyword.
- Subscript references must follow after typedef-component-1 or typedef-component-2; reference modification can then be specified after the subscript; for example, ptr1::array1(2)(2:1). For a more detailed example, see Pointer Examples.
General Rules Format 2
- If typedef-name-2 or typedef-component-2 are of usage pointer, you can also use :: for further dereferencing.
General Rules All Formats
- Untyped pointers that specify the DATA keyword must also specify reference modification; for example, ptr1::DATA(1:10) or DATA(1:10) AT ptr1.
- For typed pointers, DATA without a reference modification expression refers to the complete data held by the pointer.
- In general, if a receiving operand and sending operand are typed, then the types must match. However, format 1 does allow pointer coercion: the AS clause allows the non matching type to be coerced to the other. Coercion can also be used to change the type of the pointer to match the typedef-component. If the underlying data does not match the coerced type then the behavior is undefined.
- An exception to the previous rule is that if a pointer points to a type of PIC X, that pointer can point to any data defined as PIC X(n), and vice versa.