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Re: CLP pgm with 2 paramters intermittently gettinggarbagewhencalled from AJS



fixed

Paul:

Think about it -- it is because you "declare" the type, length (and decimal places) of each parameter when you create a command.

When you use the CALL command, it accepts a list of zero or more "generic" parameters. The CALL command has no way to know, for example, that the second parameter should be "packed decimal" 15 digits, 0 to the right of the decimal.

Hope this helps,

Mark S. Waterbury

> On 4/11/2014 10:04 PM, Steinmetz, Paul wrote:
Buck, Rob, Mark, and everyone else who chimed in.

Good explanations.
I found some good documentation from CALL help text, also in V7R1 info center (see below).
>From previous info in this thread, is it still correct that if you make a CMD instead of doing a CALL, then this 32 byte issue goes away?
CALL is a CMD, so why would other commands be treated differently?

Also, I opened PMR with IBM to confirm the 32 byte issue, using CALL or CMD
IBM has a doc. Passing parameters that are longer that 32 characters between two CL programs requires special handling.
http://www-01.ibm.com/support/docview.wss?uid=nas8N1014767
IBM confirmed this is not only from a command line, but can also occur pgm to pgm.
As a workaround, IBM is actually suggesting to make the parameter in the calling program 1 byte longer than the parameter in the called program.
IBM also confirmed that using a CMD instead of a call should not have the issue, however, not finding any documentation to confirm/support this.

Question, is there a source search I could perform that would find any program that has a call with a parameter defined with a length of 32 bytes or more.
This may take some coding, but will be worth time spent.

Call help text
Parameters can be passed and received as follows:
o Character string constants of 32 bytes or less are always passed
with a length of 32 bytes (padded on the right with blanks). If
a character constant is longer than 32 bytes, the whole length
of the constant is passed. If the parameter is defined to
contain more than 32 bytes, the calling program must pass a
constant that contains exactly that number of bytes. Constants
longer than 32 characters are not padded to the length expected
by the receiving program.

The receiving program can receive less than the number of bytes
passed (in this case, no message is sent). For example, if a
program specifies that 4 characters are to be received and
ABCDEF is passed (padded with blanks in 26 positions), only ABCD
is accepted and used by the program. Quoted character strings
can also be passed.

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Buck Calabro
Sent: Friday, April 11, 2014 12:32 PM
To: midrange-l@xxxxxxxxxxxx
Subject: Re: CLP pgm with 2 paramters intermittently gettinggarbagewhencalled from AJS

On 4/11/2014 10:31 AM, Steinmetz, Paul wrote:
One last question.
Does the 32 character clear issue on a SBMJOB only apply to CLP.
No.

Is RPG, RPGLE, etc also impacted?
Yes.

Imagine writing a program in any language that has to receive an arbitrary message and store it in memory. This is what the command processor has to do in order to pass a pointer to a block of memory to the callee. It looks at the message, infers the data type and length and then allocates memory based on those inferences. Having allocated a block of memory, it shares the pointer with the callee, which then maps (like an RPG data structure with OVERLAY) its parameter to that memory block.

So the only question is this: What size variable should my arbitrary message processor set aside? We could allocate 64k, but if the average message is only 10 bytes, that's a lot of wasted space. We could allocate 10 bytes, but when we get a larger message we'd have to re-allocate the memory which takes time. The way to optimise the variable size then, is to analyse the incoming messages and choose a size that covers enough standard deviations to provide a tradeoff between wasting memory and wasting processor time.

IBM chose 32 bytes as that tradeoff point.

When I CALL a program - in any language - from the command line (or SBMJOB), the command processor allocates 32 bytes for a character variable, and re-allocates to the larger size if it finds that the supplied argument is larger than that. Numbers are always packed and put into a 15,5 memory block.

The problem comes when the callee defines a larger parameter, say 50 bytes and the command line supplies fewer than 50 characters. The command processor allocates, clears and loads 32 bytes, properly leaving any memory after that alone. The callee gets a pointer to 32 bytes of properly initialised memory and proceeds to process 50 bytes from that memory block.

The caller (the command processor) did not touch bytes 33 - 50 of that block, and no one knows for sure what previous memory operations did.
So what's in there might be blanks or it might not be. It's variable depending on the state of the memory pool your job is running in.

--buck
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