Address constant

The V-type constant reserves storage for the address of a location in a control section that is defined in another source module. Use the V-type address constant only to branch to an external address, because link-time processing might cause the branch to be indirect (for example, an assisted linkage in an overlay module). That is, the resolved address in a V-type address constant might not contain the address of the referenced symbol. In contrast, to refer to external data, use an A-type address constant whose nominal value specifies an external symbol identified by an EXTRN instruction.

Because you specify a symbol in a V-type address constant, the assembler assumes that it is an external symbol. A value of zero is assembled into the space reserved for the V-type constant; the correct relocated value of the address is inserted into this space by the linkage editor before your object program is loaded.

The symbol specified (see 1 in Table 1) in the nominal value subfield does not constitute a definition of the symbol for the source module in which the V-type address constant appears.

The symbol specified in a V-type constant must not represent external data in an overlay program.

Table 1. V address constants
Subfield	Value	Example
1. Duplication factor	Allowed
2. Type	V
3. Type Extension	D
4. Program type	Allowed
5. Modifiers Implicit length: (length modifier not present)	V-type: 4 bytes VD-type: 8 bytes	VL4(ExtSym)
Alignment: (Length modifier not present)	V-type: Fullword VD-type: Doubleword
Range for length:	V-type: 4 or 3 only VD-type: 3, 4, or 8 (no bit length)
Range for scale:	Not allowed
Range for exponent:	Not allowed
6. Nominal value Represented by:	A single external symbol	`DC V(MODA)` 1 `DC V(EXTADR)` 1
Enclosed by:	Parentheses
Exponent allowed:	No
Number of values per operand:	Multiple
Padding:	None
Truncation of assembled value:	Not applicable

In the following example, 12 bytes are reserved, because there are three symbols. The value of each assembled constant is zero until the program is link-edited.

VCONST   DC              V(SORT,MERGE,CALC)

z/OS only: To specify a list of conditional external symbols to be resolved by the Binder, the following syntax is used:

VCONST DC V(FUNCA:FUNCB:FUNCC)

The Binder will attempt to resolve the external reference to FUNCA. If FUNCA is not available, the Binder attempts to resolve the reference to FUNCB. If FUNCB is not available, FUNCC. Finally, if FUNCC is not available, the external references are flagged as unresolved.