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Call CILE Service Program from free-form RPG

I'm trying to call a very simple C ILE service program from RPG.

The C function looks like this:

int Add(const int a, const int b) {
 return a + b;
}

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I'm able to call it using the RPG code below...

     h dftactgrp(*no) BndDir('MYLIB/MYBNDDIR')

     d HelloWorldPR    pr              *   ExtProc('HelloWorld')
     d AddPR           pr             5  0 ExtProc('Add')
     d   num1                         5i 0 const
     d   num2                         5i 0 const
     d ReturnNumberPR  pr             5i 0 ExtProc('ReturnNumber')

     d result          s              5i 0 Inz(*zero)
     d n1              s              5i 0 Inz(*zero)
     d n2              s              5i 0 Inz(*zero)
      /Free
       n1 = 3;
       n2 = 4;
       result = AddPR(n1:n2);

       *inlr = *on;
      /End-Free

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However, when I step through the C function in debug, instead of 3 and 4, a and b equal 319266122 and 1593839616. So when they get added together they result in a decimal-data error. What do I have to do to get the parms in a format that jives w/ the C function?

Gary Patterson, CISSP

An RPG "5i" is a 2-byte (the "5" means that it holds up to 5 digits) integer. A C "int" is a 4-byte signed integer. Declare the RPG var as "10i" or the C var as "short".

ILE C vs ILE RPG Numeric Data Types

C int = RPG 10I 0
C short [int] = RPG 5I 0
C unsigned [int] = RPG 10U 0
C unsigned short [int] = RPG 5U 0
C float = RPG 4F
C double = RPG 8F
C long [double] = RPG 8F

- Gary Patterson

joeschuh

ASKER

Gary, thank you very much. That is good information.

However, defining my RPG fields "n1" and "n2" as 10i 0 didn't change the fact that when I step through the call, I can see within the C function the values "a" and "b" equal really really large numbers, and I'm just trying to pass 3 and 4.

In debug, before I step into the C function call n1 and n2 (in my RPG program) equal 3 and 4. When I step into the function, the parameters a and b (of the C function) equal 319,268,938 and 1,593,839,616.

I basically left the c function defined w/ ints, and changed the RPG fields that i use to call the function to 10i's.

Unless I'm misunderstanding something here.

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Gary Patterson, CISSP

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joeschuh

ASKER

Both solutions provided good info. My problem ended up actually being that I was adding addresses together instead of the actual values. I was passing the parameters byref in the RPG code. I added the keyword "value" and everything worked fine.

Thanks to you both.

joeschuh

ASKER

d AddPR pr 5 0 ExtProc('Add')
d num1 5i 0 value
d num2 5i 0 value