Adding Subprocedures to a Service Program, Revisited

September 11, 2002 Timothy Prickett Morgan

Hey, Ted:

Regarding your article, “Adding Subprocedures to a Service Program,” there’s a question I’ve always wondered about.

Why is the *CURRENT/*PRV way of handling new exports, such as this example:

STRPGMEXP PGMLVL(*CURRENT)
EXPORT SYMBOL('ONEMORETHAN')
EXPORT SYMBOL('TWICE')
EXPORT SYMBOL('ONETHIRDOF')
ENDPGMEXP
STRPGMEXP PGMLVL(*PRV)
EXPORT SYMBOL('ONEMORETHAN')
EXPORT SYMBOL('TWICE')
ENDPGMEXP
STRPGMEXP PGMLVL(*PRV)
EXPORT SYMBOL('ONEMORETHAN')
ENDPGMEXP

so popular compared to the hard-coded signature method, where you only keep one export list, as shown in this example:

STRPGMEXP PGMLVL(*CURRENT) SIGNATURE("MATH")
EXPORT SYMBOL('ONEMORETHAN')
EXPORT SYMBOL('TWICE')
EXPORT SYMBOL('ONETHIRDOF')
ENDPGMEXP

You have to keep the exports in the same order and add news ones at the end anyway, so I don’t see the advantage of using *PRV signatures.

— Barbara Morris

RPG Compiler Development, IBM

I’m not sure why the SIGNATURE(*GEN) method is so popular, but I’ll take a guess: That’s the way the writers for the tech magazines learned it first.

Whatever the reason, the hard-coded signature method makes sense and does seem easier. If other readers know of a down side to hard-coded signatures, or otherwise have feelings about this issue, I hope they will e-mail me .

I tested the hard-coded signature with the example in the original tip, and it worked fine. I was able to add more exports to the service program without getting signature level checks.

— Ted

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