Re: Adding to a Service Program

Yup - that was one of the speed compromises.

The parameters are (effectively) pushed on the stack and popped by the called routine. That's why it is important to never try to reference a parm that wasn't actually passed. There's a pretty good chance that there will be data in that spot on the stack and you can get some "interesting" bugs introduced by sloppy programming that ignores %Parms!

One small addition top Mark's comment on signature. It is based as he says on sequence and name UNLESS the binder language specifies a different hard coded signature. Which is what IBM do for most System Service Programs. IBM's ones that don't have a reardable signature are a legacy of an early "ooopssss" in the the design cycle.


Jon P.

On Sep 30, 2022, at 12:13 PM, Mark Waterbury <mark.s.waterbury@xxxxxxxxxxxxx> wrote:

There IS NO "parameter list map" -- the service program level checking is strictly based on the names of the exported procedures or functions, and the order they are exported. That's it! It does nothing for you to detect if you pass an incorrect number of parameters.

On Friday, September 30, 2022 at 01:18:01 PM EDT, x y <xy6581@xxxxxxxxx> wrote:

Yes, by signature would have been better, but then every call to a given
member (i.e., subprocedure) in a service program would have to test the
signature before calling it; that action, even if it's efficient, will
eventually generate a lot of overhead simply based on the number of called
to service programs system-wide. The system likely builds a table in
memory with member parameter addresses when a service program is
instantiated and this will shorten the code path for each call.

Adding a new member to the end of the binder language preserves the
original parameter list map. Activated service programs won't be affected.

Wouldn't the *IMMED/*DEFER logic get busted too?

Yes, by position is a bit quirky but that's the way the database works and
we've managed that.

On Fri, Sep 30, 2022 at 10:02 AM Tom Daly via MIDRANGE-L <
midrange-l@xxxxxxxxxxxxxxxxxx> wrote:

It's always seemed to me that binder is stub of an idea that was never
completed. Unlike level checks with files, for a srvpgm a third object is
introduced for "level checking". I've always thought this was odd since it
didn't add much. Binder would be more useful if it referred to the
signature rather than the ordinal position and if the signature was
generated and tied to the parameters.
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