HLASM Language Reference

WXTRN Instruction
ALBL1 USING DSECTA,14
USING
DSECTB,ALBL1.A
.
.
ALBL2 USING DSECTA,ALBL1.A
.
BLBL1 USING DSECTA,ALBL2.A
.
DROP
ALBL2
.
DSECTA DSECT
A DS A
DSECTB DSECT
B DS A
A dependent USING is not dependent on another dependent USING. It is
dependent on the ordinary or labeled USING that is finally used to resolve the
address. For example, the USING at BLBL1 is dependent on the ALBL1 USING.
Remember that all dependent USINGs must eventually be based on an ordinary or
labeled USING that provides the base register used for base-displacement
resolutions.
WXTRN Instruction
The WXTRN statement identifies “weak external” symbols referred to in a source
module but defined in another source module. The WXTRN instruction differs from
the EXTRN instruction (see “EXTRN Instruction” on page 189) as follows:
The EXTRN instruction causes the linker to automatically search libraries (if
automatic library call is in effect) to find the module that contains the external
symbols that you identify in its operand field. If the module is found, linkage
addresses are resolved; the module is then linked to your module, which
contains the EXTRN instruction.
The WXTRN instruction suppresses automatic search of libraries. The linker
only resolves the linkage addresses if the external symbols that you identify in
the WXTRN operand field are defined:
– In a module that is linked and loaded along with the object module
assembled from your source module, or
– In a module brought in from a library because of the presence of an
EXTRN instruction in another module linked and loaded with yours.
┌─,───────────────┐
►►──┬─────────────────┬──WXTRN─── ▼ ─external_symbol─┴────────────────►◄
└─sequence_symbol─┘
sequence_symbol
is a sequence symbol.
Chapter 5. Assembler Instruction Statements 229