Reader Feedback and Insights: Binder Language

September 13, 2002 Timothy Prickett Morgan

Hey, Ted:

Great article, Ted! It was a very clever presentation, and I enjoyed reading it. I do have one comment and one question, though. I don’t always create binder source when I first create a service program. When I’ve later added another procedure, I create the service source with a *CURRENT signature and a *PRV signature that defines the original situation and that seems to prevent any problems with needing recompiles.

Here’s my question: Someone once told me that when I created new procedures, or at least when I create the binder source, that new procedures must be added below the existing procedures for the *CURRENT group, or older programs would crash. Is this true? I see that you put the third procedure in front of the original one.

— John

I’m glad you enjoyed the article. You are correct that the new procedures should go at the bottom of the export list. I added the third export at the top when I was typing up the tip.

A few other people wrote in with similar questions and comments. Jon Paris, of partner400.com, mentioned (rightfully) that I should have made this clear. Here is his comment:

What you didn’t say was that the sequence of exports in *Current is what governs the order of the slots in the service program. This is what makes it vital that you add all additional procedures to the end of the *Current list. As far as the *PRV lists are concerned, they are only used to generate signatures–they have no impact on slot usage.

Say the original set of exports was A, B, F and current is changed to A, B, C, F–people do this because it is tidy to put things in order–it appears that a previous signature of A, B, C will produce the desired result. Of course it won’t, and worse still there’s no signature violation, but whenever programs bound to the old version call procedure C they will be getting F instead.

I suspect that you know this, but thought I’d mention it as we’ve seen so many customers make this mistake.

Thanks to everybody who wrote in about this tip. I hope this helps.

— Ted

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