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

I have been thinking the same thing for years but the whole issue is really
mute now. Programs should be coded with SQL. All these issues vanish and we
get so much more.


On Thu, Nov 1, 2012 at 10:43 AM, Jeff Crosby <jlcrosby@xxxxxxxxxxxxxxxx

wrote:

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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