Calling RPG procedure from C++

Question

I am busy with a C++ project on IBM i and is trying to call an RPG procedure that is in a service program, but I am not sure how to do that.

I only find examples on the internet and the documentation that shows how to call an RPG program (*PGM) object by defining it as follows:

extern "OS"
{
    void RPGPROGRAM(void);
}

int main()
{
    RPGPROGRAM();
    return 0;
}

The documentation says they are calling an RPG "procedure" but if you look at the actual source it is just a RPG program (*PGM) object that they call from within C++ using #pragma map.

Lets say I have the following RPG service program (lets name it RPGSP) with a procedure named rpg_doSomething defined in it:

ctl-opt nomain;

dcl-proc rpg_doSomething export;
  dcl-pi *n int(10);
    dcl-parm p_test char(20);
  end-pi;

  p_test = "It Works!!";

  return 1;

end-proc;      

How should I declare and call the above procedure in my C++ program?

I have tried declaring it within the extern block but it ends up looking for the rpg_doSomething object at runtime and cannot find it. I have also tried binding the service program to the C++ program when compiling but that does not work either.

Any help on this would be appreciated.

Answer 1

First off which C++ compiler are you using?

The native ILE one? Then it should be pretty easy. Pretty sure you just need: extern "RPG" on the function declaration.

Or the AIX on in PASE? Then take a look at Calling ILE procedures

One thing to note, RPGLE is case insensitive and by default, uppercases names. While C/C++ is case sensitive. Your C++ program needs to be calling RPG_DOSOMETHING or you need to apply a case sensitive name to the RPG procedure using EXTPROC('rpg_DoSomething')