Re: the problem with passing a const reference -- RPG400-L

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Steve Richter wrote:

Carlos,

Thanks for pointing this out.  Hans's response primarily addresses the use
of global variables.  What I am saying is that const can cause problems
whenever the calling proc uses the same variable on more than one parm of a
proc:
   Calc_New_Qty( qty1: qty1 ) ;

 d Calc_New_Qty   pi
 d OutQty                  7p 2
 d InQty                   7p 2  const
  /free
       OutQty    = 0 ;  // this can affect any other pass by
                        // reference parm.  const or no const!
       ...
  /end-free

I think passing any numeric or small char variable by const reference is a
bug waiting to happen.  passing by value is safer and performs just the
same.

In this example, you'd also have problems even if INQTY were a normal reference parameter, and so the problem isn't limited to CONST parms. As I discussed earlier, any time you can access some piece of storage from two (or more) different names (AKA aliasing), you run the risk of having some "fun" debugging sessions. Aliasing bugs crop up in a lot of places, especially if you're using pointers and dynamically allocated storage.

Cheers! Hans

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