[netrexx-pipelines] Null Pointer Exception Journey Notes

[Colin K <CK-...@im...>]

Just thought I would post some notes about my recent foray into trying 
to solve a null pointer exception problem I have with one of my 
hostbyname test scripts.

When using the V.308 distribution on www.netrexx.org when one compiles a 
.nrx file note that the eyecatcher says 3.08GA with a build date of 
2019-09-06

    Z:\NetRexx-3.08-GA\bin>nrc hostbyname
    java -cp
    "Z:\NetRexx-3.08-GA\lib\jansi-1.18.jar;Z:\NetRexx-3.08-GA\bin;Z:\NetRexx-3.08-GA\lib\*;;;Z:\NetRexx-3.08-GA\lib\NetRexxF.jar;."
    -Dnrx.compiler=ecj org.netrexx.process.NetRexxC  hostbyname
    NetRexx portable processor 3.08-*GA* build 1,582-*20190906*-1850
    Copyright (c) RexxLA, 2011,2019.   All rights reserved.
    Parts Copyright (c) IBM Corporation, 1995,2008.
    Program hostbyname.nrx
       === class hostbyname ===
         method run
           signals ThreadQ
           overrides stage.run
    Compilation of 'hostbyname.nrx' successful


I want to see if the recent changes to RexxIO that addressed some null 
pointer exceptions would resolve my issues with one of my pipe test 
scripts which gives a null pointer exception but works fine on its own.

This fails with a null pointer exception (it should fail but not with a 
null pointer exception):

    pipe (hbntest5) literal bogus.bogus | hostbyname | console |
    compare: compare equal /PASS/ notequal /FAIL/ | console ? literal
    93.184.216.34 | compare:

    Z:\NetRexx-3.08-GA\bin>java hbntest5
    < Input record 1: Unable to determine IP address for bogus.bogus >
    FAIL
    java.lang.NullPointerException
             at hostbyname.run(hostbyname.java:104)
             at org.netrexx.njpipes.pipes.ThreadPool.run(ThreadPool.java:76)
             at java.lang.Thread.run(Unknown Source)
    Exiting due to uncaught Exception null


This works:

    Z:\NetRexx-3.08-GA\bin>pipc "(hbntest5a) literal bogus.bogus |
    hostbyname | console"
    ( hbntest5a  ) literal bogus.bogus | hostbyname | console

    Z:\NetRexx-3.08-GA\bin>java hbntest5a
    < Input record 1: Unable to determine IP address for bogus.bogus >


Interestingly all my hbntest1-4 scripts have compare filters and they 
work just fine.  There is something about this one that causes a 
problem.  Now hbntest5 is the first script that generates output based 
on a caught UnknownHostName exception but I don’t see how that would be 
the problem as it appears to work just fine without the compare section.

Now I am not in any way git literate.  I went to sourceforge.net and did 
a download snapshot which appeared to work.  It got the master branch as 
of 2020-04-30 (I forgot to note the 6 digit hex number that went along 
with it).  I reran my tests but still had the same null pointer 
exception problem.   I looked at the source file for RexxIO and I can 
see the new pipeSay methods.  However, I did notice one thing – the 
eyecatcher on a compile shows 3.08-BETA2 with a date of 2019-09-08.

    Z:\NetRexx-3.08-GA\bin>nrc -version
    java -cp
    "Z:\NetRexx-3.08-GA\lib\jansi-1.18.jar;Z:\NetRexx-3.08-GA\bin;Z:\NetRexx-3.08-GA\lib\*;;;Z:\NetRexx-3.08-GA\lib\NetRexxC.jar;."
    -Dnrx.compiler=ecj org.netrexx.process.NetRexxC  -version
      +++ Warning: Unknown command option '-version' ignored
    NetRexx portable processor 3.08-*BETA2* build 1,202-*20190808*-1303
    Copyright (c) RexxLA, 2011,2019.   All rights reserved.
    Parts Copyright (c) IBM Corporation, 1995,2008.


So I figured that I had some old code and needed to recompile/rebuild 
the NetRexx code from this snapshot.  According to the manual (section 
29.2) I should make “netrexx/netrexxc/trunk” the current directory 
before running the compile command.  The only problem is there is no 
such directory in my snapshot.  For fun, I made my current directory the 
root of the NetRexx snapshot and then ran the compile command.  That 
seemed to work fine (other than not being able to find tools.jar).

    Z:\NetRexx-3.08-GA>java -jar ant/ant-launcher.jar compile
    Unable to locate tools.jar. Expected to find it in C:\Program
    Files\Java\jre1.8.0_221\lib\tools.jar
    Buildfile: Z:\NetRexx-3.08-GA\build.xml

    prepare:

    . . .snip. . .

    compile:

    BUILD SUCCESSFUL
    Total time: 3 minutes 12 seconds

    Z:\NetRexx-3.08-GA>


I ran another nrc but it shows the same BETA2 date eyecatcher. . .

. . .and  test script still failed.  :-(

    Z:\NetRexx-3.08-GA\bin>pipc hbntest5
    pipe (hbntest5 ) literal bogus.bogus | hostbyname | console |
    compare: compare equal /PASS/ notequal /FAIL/ | console ? literal
    93.184.216.34 | compare:

    Z:\NetRexx-3.08-GA\bin>java hbntest5
    < Input record 1: Unable to determine IP address for bogus.bogus >
    FAIL
    java.lang.NullPointerException
             at hostbyname.run(hostbyname.java:107)
             at org.netrexx.njpipes.pipes.ThreadPool.run(ThreadPool.java:60)
             at java.lang.Thread.run(Unknown Source)
    Exiting due to uncaught Exception null


So – it looks like I need to spend some time and get some “git” skills 
under my belt. :-)

Time to crack open a git book.

A fun and interesting journey.

Cheers
Colin