ALIAS instruction

The ALIAS instruction specifies alternate names for the external symbols that identify control sections, entry points, and external references. The instruction has nothing to do with the link-time aliases in libraries.


>>-symbol--ALIAS--alias_string---------------------------------><

symbol

Is an external symbol that is represented by one of the following:

An ordinary symbol
A variable symbol that has been assigned a character string with a value that is valid for an ordinary symbol

alias_string

Is the alternate name for the external symbol, represented by one of the following:

A character constant in the form C'aaaaaaaa', where aaaaaaaa is a string of characters each of which has a hexadecimal value of X'42' - X'FE'.
A hexadecimal constant in the form X'xxxxxxxx', where xxxxxxxx is a string of hexadecimal digits, each pair of which is in the range X'42' - X'FE'.

The ordinary symbol denoted by symbol must also appear in one of the following in this assembly:

The name entry field of a START, CSECT, RSECT, COM, or DXD instruction
The name entry field of a DSECT instruction and the nominal value of a Q-type offset constant
The operand of an ENTRY, EXTRN, or WXTRN instruction
The nominal value of a V-type address constant

Note: All external symbols identified by EXTRN, WXTRN, ENTRY and V-cons statements must belong to an owning section definition.

The assembler uses the string denoted by alias_string to replace the external symbol denoted by symbol in the external symbol dictionary records in the object module. Because the change is made only in the external symbol dictionary, references to the ALIASed symbol in the source program must use the original symbol. If the string is shorter than eight characters, or 16 hexadecimal digits, it is padded on the right with EBCDIC spaces (X'40'). If the string is longer than eight characters, it is truncated. Some programs that process object modules do not support external symbols longer than 8 characters.

z/VM and z/OS: If the extended object format is being generated (GOFF assembler option), the alias_string can be up to 256 characters, or 512 hexadecimal digits.

The following examples are of the ALIAS instruction, and show both formats of the alternate name denoted by alias_string.

EXTSYM1  ALIAS           C'lower1'
EXTSYM2  ALIAS           X'9396A68599F2'

The alias_string must not match any external symbol, regardless of case. References to an ALIASed symbol must be made using the original name; the original symbol is changed only in the external symbol dictionary. For example, you write

        EXTRN    EXTSYM1

to refer to the external symbol 'lower1'.

Aliased names are not checked against ALIASes for possible duplicates or conflicts.