[SOLVED] Link Error trying to call BPX1WRT in assembler on z/OS

Link Error trying to call BPX1WRT in assembler on z/OS

I am writing some assembler code to do 'Hello World', but I want to write to stdout in UNIX System Services and not a WTO or PUT to a DDName.

I am using 'as' and 'ld' without any special options to assemble and link, e.g.

as -mlist hw.asm >hw.lst
ld hw.o

and I expect I need to pull in the library code for BPX1WRT from somewhere, but I can't find it in the documentation. I end up with:

 Assembler Done No Statements Flagged
 IEW2457E 9208 SYMBOL BPX1WRT UNRESOLVED.  NO CALL LIBRARY SPECIFIED.
 IEW2665S 40FF MODULE *NULL*  IS NON-EXECUTABLE AND WAS NOT SAVED BECAUSE
          STORENX=NEVER.
IEW5033 The binder ended with return code 12.

I am coding this up as re-entrant code. Here's the code (I expect there are addressability bugs in here since I haven't got it linking yet)

        PRINT ON,GEN,DATA
HELLO   CSECT
*
* Prolog
*
        SAVE (14,12)
        BASR R12,0
        USING *,R12
        STORAGE OBTAIN,LENGTH=DYNSIZE,ADDR=(R11)
        USING DYNAREA,R11
        LA R2,SAVEA
        ST R2,8(,R13)
        ST R13,SAVEA+4
        LR R13,R2
*
* Body
* Write Hello World to STDOUT
*
        MVC RECORD,=C'Hello World'
        MVC RECLEN,RECSIZE
        LA  R15,RECORD
        ST  R15,RECADDR
        CALL BPX1WRT,                                                  +
               (STDOUT,                                                +
               RECORD,                                                 +
               BPXALET,                                                +
               RECLEN,                                                 +
               RV,                                                     +
               RC),                                                    +
               VL,MF=(E,PLIST)

*
* Epilog
*
        STORAGE RELEASE,LENGTH=DYNSIZE,ADDR=(R11)
        RETURN (14,12),RC=0
        LTORG
*
* Statics (constants)
*
STDOUT  DC F'0'
STDIN   DC F'1'
STDERR  DC F'2'
BPXALET DC F'0'
*
* Dynamic (storage obtain'ed) area
*
DYNAREA DSECT
DYNSIZE EQU DYNEND-*
*
* Stack save area always first
*
SAVEA   DS 18F
*
* Working storage
*
RECSIZE EQU RECEND-*
RECORD  DS CL80
RECLEN  DS F
RECEND  EQU *
RECADDR DS A
RV      DS F
RC      DS F
PLIST   DS 10A * Is this enough?
*
* End of working storage
*
DYNEND  EQU *
*
* Equates
*
R0      EQU 0
R1      EQU 1
R2      EQU 2
R3      EQU 3
R4      EQU 4
R5      EQU 5
R6      EQU 6
R7      EQU 7
R8      EQU 8
R9      EQU 9
R10     EQU 10
R11     EQU 11
R12     EQU 12
R13     EQU 13
R14     EQU 14
R15     EQU 15
        END

Solution

You are using the CALL macro instead of the LINK (or better LINKX) macro to invoke BPX1WRT. This will STATICALLY include the load module for BPX1WRT into your linked program. Use LINKX instead to dynamically load and execute BPX1WRT.

The link error is because you do not have the system library where BPX1WRT lives in the SYSLIB DD of the link step.