topic Re: %DCL-E-INVIFNEST, invalid IF-THEN-ELSE nesting structure or data inconsistency in Operating System - OpenVMS

%DCL-E-INVIFNEST, invalid IF-THEN-ELSE nesting structure or data inconsistency

Debasis Bhar — Tue, 18 Aug 2009 07:42:28 GMT

Script is
====
$ para1 = f$edit(p1,"upcase,trim")
$ IF ("''para1'" .eqs. "ONLINE") .OR. ("''para1'" .eqs. "1") THEN goto LOOP_DISK
====
I am getting the below error message but it is going to LOOP_DISK label. Any idea how i can correct this error message?

%DCL-E-INVIFNEST, invalid IF-THEN-ELSE nesting structure or data inconsistency

Re: %DCL-E-INVIFNEST, invalid IF-THEN-ELSE nesting structure or data inconsistency

Heinz W Genhart — Tue, 18 Aug 2009 07:56:13 GMT

Hi Debasis Bhar

I copied the two lines of code into a commandfile and executed it without any error message. The two lines are correct (only a label loop_disk is missing).

Is this the whole script? Can you supply the rest of the script

Regards

Geni

Re: %DCL-E-INVIFNEST, invalid IF-THEN-ELSE nesting structure or data inconsistency

Debasis Bhar — Tue, 18 Aug 2009 08:46:34 GMT

here is the error message in set verify mode.. p1 is online..

$ para1 = f$edit(p1,"upcase,trim")
$ IF ("ONLINE" .eqs. "ONLINE") .OR. ("ONLINE" .eqs. "1") THEN goto LOOP_DISK
%DCL-E-INVIFNEST, invalid IF-THEN-ELSE nesting structure or data inconsistency
$ LOOP_DISK:
...
...
...

Re: %DCL-E-INVIFNEST, invalid IF-THEN-ELSE nesting structure or data inconsistency

Richard Brodie_1 — Tue, 18 Aug 2009 08:55:34 GMT

The error is likely in one of the lines you haven't shown.

$ @T
$ IF 1 then goto a
%DCL-E-INVIFNEST, invalid IF-THEN-ELSE nesting structure or data inconsistency
$ a: exit

$ type t.com

$ IF 1 then goto a
$ endif ! Pointless endif
$ a: exit

Re: %DCL-E-INVIFNEST, invalid IF-THEN-ELSE nesting structure or data inconsistency

Kris Clippeleyr — Tue, 18 Aug 2009 09:01:20 GMT

Debasis Bhar,

Is it possible that by taking the branch (goto LOOP_DISK) you're jumping out of or into an IF-THEN-ELSE-ENDIF construction?

I've copied your snippet of DCL-code, added 4 lines:

$ ENDIF
$ EXIT
$LOOP_DISK:
$ write sys$output "Reached LOOP_DISK"

and then by executing this procedure, I get the "invalid IF-THEN-ELSE".
If I remove the "$ ENDIF" line, all is well.

So, I suggest you check the line between the "goto LOOP_DISK" and the LOOP_DISK label for ill-constructed IF-THEN-ELSE-ENDIFs.

Regards,
Kris (aka Qkcl)

Re: %DCL-E-INVIFNEST, invalid IF-THEN-ELSE nesting structure or data inconsistency

Willem Grooters — Tue, 18 Aug 2009 10:11:35 GMT

In searching for a label, DCL will do the comparison in IF statements and only check the codepath that conforms the outcome. If you jump out of, or into a IF_THEN_ELSE_ENDIF block, it could cause this and other problems.
Quite likely this is caused by a coding error.

Re: %DCL-E-INVIFNEST, invalid IF-THEN-ELSE nesting structure or data inconsistency

Jan van den Ende — Tue, 18 Aug 2009 14:23:03 GMT

Debasis Bhar,

I have not (yet) seen enough of the script to have a definite answer, but my guess would be infamiliarity with DCL history.

Once there was only the following construct:

$ IF condition THEN command

Most often "command" was something more then a single statement, and the only ways to achieve that were GOTO label, or @

When IF .. THEN [possible ELSE] was introduced, as always VMS engineering was NOT to break existing code, so, the old construct had to be retained.

The "trick" they used was to add pseudo-commands:
$ THEN
which allowes for, but does not require
$ ELSE
and had to be ended by
$ ENDIF

So, now there are TWO different IF constructs:

$ IF condition THEN command

( notice: NO !!! ENDIF )

and

$ IF condition
$ THEN
< commands >
[ $ ELSE
< other commands > ]
$ ENDIF

In the second construct only may themselves be IF constructs; although it is considered bad practise to use the first construct within the second.

My guess is that you used the first construct, but still used $ ENDIF

hth

Proost.

Have one on me.

jpe

Re: %DCL-E-INVIFNEST, invalid IF-THEN-ELSE nesting structure or data inconsistency

Hoff — Tue, 18 Aug 2009 15:00:43 GMT

Turn on procedure verification, invoke the procedure, and count the numbers of times you've entered a multi-line IF and the numbers of times you've exited a block via its matching ENDIF.

OpenVMS stinks at this sort of DCL-level tracing; it's often somewhat tedious to find these errors in non-trivial DCL procedure code. There's unfortunately no visible "nested" count for IF-THEN-ELSE stuff. Not until you blow out with the INVIFNEST error, that is.

The other approach is the brute-force approach, and involves refactoring and restructuring the code of the DCL procedure. Of cleaning up the GOSUB and GOTO and CALL and the flow control.

ps: this:

$ IF ("''para1'" .eqs. "ONLINE") .OR. ("''para1'" .eqs. "1") THEN goto LOOP_DISK

can be replaced with this:

$ IF (para1 .eqs. "ONLINE") .OR. (para1 .eqs. "1") THEN goto LOOP_DISK

And I don't know what this DCL code is doing here, but this code really smells like a parser of some sort. Possibly parsing DCL command output? And there are better ways to do that than DCL.

Re: %DCL-E-INVIFNEST, invalid IF-THEN-ELSE nesting structure or data inconsistency

Jon Pinkley — Tue, 18 Aug 2009 20:24:38 GMT

When verification is on, the "''para1'" .eqs. "ONLINE" provides more useful debugging information than para1 .eqs. "ONLINE", especially when it isn't equal.

However, when the para1 symbol value contains double quotes the "''para1'" construct does work in the general case. The := assignment and & substitution have different effects as well.

$ para1 = """this has double quotes"""
$ para2 = "''para1'"
%DCL-W-UNDSYM, undefined symbol - check validity and spelling
\HAS\
$ para3 = para1
$ para4 := "''para1'"
$ para5 = &para1
$ sho sym para*
PARA1 = ""this has double quotes""
PARA3 = ""this has double quotes""
PARA4 = "THIS HAS DOUBLE QUOTES"
PARA5 = "this has double quotes"
$

Getting symbol substitution to work when double quotes are involved is a real pain.

Re: %DCL-E-INVIFNEST, invalid IF-THEN-ELSE nesting structure or data inconsistency

Graham Burley — Tue, 18 Aug 2009 20:24:55 GMT

Get a copy of Charlie Hammond's DCL checker, written in good old DCL, perhaps from here:

http://www.digiater.nl/openvms/freeware/v80/dcl_check/

It's a useful tool to have around and will probably find the problem with your command procedure.

Re: %DCL-E-INVIFNEST, invalid IF-THEN-ELSE nesting structure or data inconsistency

John Gillings — Tue, 18 Aug 2009 22:55:59 GMT

More than likely this is due to a mismatched nesting structure somewhere between your GOTO and the target label.

A simple check for consistency in your IF-THEN-ELSE-ENDIF structures is to use SEARCH:

$ SEARCH your-procedure "IF","THEN","ELSE","ENDIF"

If you're disciplined with indentation, a mismatched block should be fairly easy to spot.

Something to watch out for is the absence of a leading "$" in the lines containing your structure verbs. For example:

$ IF condition
$ THEN
$ command
$ ENDIF

is correct, but

$ IF condition
THEN
$ command
$ ENDIF

(note missing "$" on the "THEN" verb) will fail with INVIFNEST.

Re: %DCL-E-INVIFNEST, invalid IF-THEN-ELSE nesting structure or data inconsistency

John McL — Wed, 19 Aug 2009 04:42:35 GMT

It might also be that there's a faulty construct somewhere between your IF statement and the label that you are going to.

I can't recall what the DCL parser does in the way of skipping over subroutines and I only vaguely recall that it searches forward for a statement label and then if not found, it wraps back to the start - or has this changed??

Do you, for example, have a SUBROUTINE statement without an ENDSUBROUTINE?

The DCL_CHECK.COM utility mentioned by someone else above should be able to identify these problems. (Their name has disappeared so I can't identify them without some effort.)

By the way, how is your code going to LOOP_DISK: when it has an error condition rather than a warning ? Have you said ON ERROR THEN CONTINUE ?

Re: %DCL-E-INVIFNEST, invalid IF-THEN-ELSE nesting structure or data inconsistency

Debasis Bhar — Thu, 20 Aug 2009 05:06:49 GMT

Thanks for all suggestions. These was an extra endif in between GOTO and LOOP_DISK. I removed it and now script is working fine.