Passing variable by value

[Sebastian Misiewicz]

Hi I'm trying to call service program function (MQOPEN) WebSphere MQ API on iSeries. The MQOPEN procedure is defined as

D* MQOPEN Function -- Open Object
D******************************************************

DMQOPEN           PR                  EXTPROC('MQOPEN')
D* Connection handle
D HCONN                         10I 0 VALUE
D* Object descriptor
D OBJDSC                       468A
D* Options that control the action of MQOPEN
D OPTS                          10I 0 VALUE
D* Object handle
D HOBJ                          10I 0
D* Completion code
D CMPCOD                        10I 0
......

As you can see 1st and 3rd parameters are passed by VALUE.

But the doc says that passing by value is untested and should not be used (I'm using XML -> DB2 connection) I could create an ILE RPG which accepts parameters by reference then call appropriate api with variable passed by value. But I'm wondering if it's possible to fix it ? I was trying to debug plugxml.rpgle and looks like list of parameters pointers were corrupted

       // by value argument?
       if node.xmlPrmRet = XML_IS_PARM
       and node.xmlBy = XML_BY_VAL
       and node.xmlCallAs = XML_FUNC_SRVPGM;
         pCopy = pArgv;  <------------ ?!?!?!?!!
       endif;                        

Regards Sebastian

[Former user]

Yep. Pass by value is not tested. 99.8% of all RPG programs pass by reference, therefore, a place holder was added, but never really tested completely. We will put it on the list.

For now, you are much better off simply staying with pass-by-reference, aka, forget const correctness, nobody does it anyway, except the real geeks. BTW -- you could wrap your API in by refernce and call by value on your own as well.

[Former user]

Correct answer: The new version xjservice (json version) plan support 'value' or 'const' (Common 2017).

Hack answer: However, most people do not know that anything > 16 byte 'const' or 'value is actually passed by reference anyway (compiler copy passed by ref). That is to say, xmlservice does not support by value for 1-16 bytes values. Unfortunately any packed or zoned by value will fit in 16 bytes (exotic types by value fit 2 registers <= 16 bytes). While 'glass half full', may help some people with 'value' or 'const' > 16 bytes. See this link Yips value - not what you think.

[Former user]

The new version of xmlservice 1.9.9.2 (+), supports pass by value. See the commits for how to use.

[Former user]

The new version of xmlservice 1.9.9.2 (+), supports pass by value. See the commits for how to use.