Re: Could RPG become quasi-immune to level checks (was: Are level checks still useful?)

The reason you don't have level checks in PHP (and similar environments)
is because they don't have hard-coded from/to positions in fields in the
record. When you compile an RPG program, the compiler reads the
external definition, and hard-codes the from/to positions of fields in
the record into the program. You have to recompile for it to update
these -- and therefore, level checks are an important safeguard. Without
them, if the file changes, you'll end up reading (or worse, writing)
incorrect data at incorrect places in the record, causing a big huge

mess.

Scott's post got me thinking.

Theoretically, could RPG be enhanced such that the from/to positions are
_not_ hard-coded at compile time? Instead, based on field name (whether
renamed or not), the from/to positions would be established at run time.
If so, one would also have to code updates properly, i.e., either via
"Update RecordName %Fields(blah:blah:blah);" or making sure the O specs
have no end position.

Even though I have absolutely no experience whatsoever in compiler writing
(and don't want any), I can imagine how this would fundamentally affect the
compiler.


--
Jeff Crosby
VP Information Systems
UniPro FoodService/Dilgard
P.O. Box 13369
Ft. Wayne, IN 46868-3369
260-422-7531
www.dilgardfoods.com

The opinions expressed are my own and not necessarily the opinion of my
company. Unless I say so.
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