Re: Why you shouldn't be afraid to use VARCHAR in RPGLE

I (we?) appreciate those addendums you generously provide. 

--Alan Cassidy


> On 12/10/2025 11:04 PM EST Barbara Morris <[email protected]> wrote:
> 
>  
> On 2025-12-10 12:25 p.m., James H. H. Lampert via RPG400-L wrote:
> > On 12/10/25 4:06 AM, Infodorado InfoDorado via RPG400-L wrote:
> >> The RPG compiler is a single-pass compiler
> > 
> > No, it can't be pure single-pass. If it were, then a program in which a 
> > variable is NOT defined in a D-spec, nor in the first C-spec in which it 
> > appears, would not compile, much less run. And it's trivially simple to 
> > construct an example of this (it took me about 2 minutes), and it 
> > compiles and runs just fine. I'd quote the source here, but it would 
> > likely be mangled beyond recognition.
> > 
> 
> It's a single pass through the source but it gathers information that it 
> can use multiple times.
> 
> The compiler usually allows forward-referencing, so you can code LIKE(x) 
> where x is defined later.
> 
> But for free-form definitions, the compiler requires the parameter for 
> the data-type keywords to be defined before the keyword is seen.
> 
>     dcl-s x char(con1);  // bad, con1 not defined yet
>     dcl-c con1 5;
>     dcl-s y char(con1);  // ok, con1 is defined
> 
> Where it becomes extra fun is when you have a data structure that LOOKS 
> defined.
> 
>     dcl-ds ds1;
>        subf char(10);
>     end-ds;
>     dcl-s x char(%size(ds1));  // %size(ds1) is not defined. WHAT???
> 
> RPG allows you to define the length of a data structure later, either 
> due to being on an I spec, possible an externally-described I spec, or 
> on a C spec.
> 
>       C            MOVE    *blanks       ds1        50
> 
> Almost certainly wrong columns, but you get what I mean. I'm defining 
> DS1 to have a length of 50 here, not the length of 10 that it looked 
> like it should have. Shenanigans? Yep, but upward-compatible R Us.
> 
> We have a H-spec/CTL-OPT keyword for that: DLCOPT(*NOCHGDSLEN). With 
> that keyword, the compiler doesn't allow you to change the length of the 
> data structure like that, so it's considered defined as soon as all the 
> subfields are defined.
> 
> -- 
> Barbara
> 
> -- 
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