I am working on a project to automate COBOL to generate a class diagram. I am developing using a .NET console application. I need help tracking down the procedure name where the perform statement in used in the below example.
**Z-POST-COPYRIGHT.
move 0 to RETURN-CODE
perform Z-WRITE-FILE**
How do I track the procedure name 'Z-Post-COPYRIGHT' where the procedure 'Z-write-file' is called? The only idea I could think of in terms of COBOL is through indentation as the procedure names are always indented. Ideally in the database, the code should track the procedure name after the word 'perform' and procedure under which it is called (in this case it is Z-POST-COPYRIGHT).
I assume you want to do this "on your own" without external tools (a faster approach can be found at the end).
You first have to "know" your source:
which compiler was it compiled with (get a manual for this compiler)
which options were used
Then you have to preparse the source:
include copybooks (doing the given REPLACING rules if any)
if the source is in free-form reference format: concatenate contents of last line and current line if you find a - in column 7
check for REPLACE and change the result accordingly
remove all comments (maybe only * and \ in column 7 in fixed-form reference format or similar (extensions like "variable" format / "terminal" format", ... exist, maybe only inline comments - when in free-form reference-format, otherwise maybe inline comments *> or compiler specific extensions like |) - depending on the further re-engineering you want to do it could be a good idea to extract them and store them at least with a line number reference
The you finally can track the procedure name with the following rule:
go backwards to the last separator period (there are more rules but the rule "at least one line break, another period, a space a comma or a semicolon" [I've never seen the last two in real code but it is possible" should be enough)
check if there is only one word between this separator period and the next
if this word is no reserved COBOL word (this depends on your compiler) it is very likely a procedure name
Start from here and check the output, then fine grade the rule with actual false positives or missing entries.
If you want to do more than only extract the procedure-names for PERFORM and GO TO (you should at least check the sources for PERFROM ... THRU) then this can get to a lot of work...
Faster approach with external tools:
run a COBOL compiler on the complete sources and tell it to do the preparsing only - this way you have the big second point solved already
if you have the option: tell the compiler or an external tool to create a symbol table / cross reference - this will tell you in which line a procedure is and its name (you can simply find the correct procedure by comparing the line)
Just a note: You may want to check GnuCOBOL (formerly OpenCOBOL) for the preparsing and/or generation of symbol tables/cross-reference and/or printcbl for a completely external tool doing preparsing and/or cobxref for a complete cross reference generation.
Related
I would like to know how to get the current paragraph name in COBOL (using MVS Enterprise COBOL V4.2 here).
Let's say I have this code in the PROCEDURE DIVISION :
MAIN-LOGIC.
MOVE SPACE TO ABT-MSG
PERFORM PARAGRAPH-1
PERFORM PARAGRAPH-2
GO TO CLOSE-PROGRAM.
*
* SEARCH FOR A VALUE IN AN ARRAY AND GET THE RELATED INDEX
*
PARAGRAPH-1.
MOVE 42 TO SEARCH-VALUE
PERFORM VARYING I-SEARCH FROM 1 BY 1
UNTIL SOME-ARRAY(I-SEARCH) = SEARCH-VALUE
IF (I-SEARCH = MAX-ARRAY-POSITION)
MOVE SEARCH-ABORT TO ABT-MSG
MOVE 'PARAGRAPH-1' TO ABT-LOC
GO TO CLOSE-PROGRAM
END-IF
END-PERFORM
DISPLAY 'VALUE WAS FOUND AT POSITION ' I-SEARCH '.'.
*
* STORE A NEW VALUE AT THE END OF AN ARRAY
*
PARAGRAPH-2.
MOVE 42 TO STORAGE-VALUE
ADD 1 TO I-STORAGE
IF (I-STORAGE > MAX-ARRAY-POSITION)
MOVE STORAGE-ABORT TO ABT-MSG
MOVE 'PARAGRAPH-2' TO ABT-LOC
GO TO CLOSE-PROGRAM
END-IF
MOVE STORAGE-VALUE TO SOME-ARRAY(I-STORAGE).
*
* CLOSE THE PROGRAM
*
CLOSE-PROGRAM.
IF ABT-MSG > SPACE
DISPLAY ABT-MSG
DISPLAY '(FOUND IN ' ABT-LOC ')'
MOVE 20 TO RETURN-CODE
ELSE
DISPLAY SUCCESS-MESSAGE
END-IF
STOP RUN.
I would like to be able to access the current paragraph name (and store it in ABT-LOC) instead of having to write it.
Is there a COBOL system variable to do so, like 'CURR-PARA-NAME' or something ?
Thank you.
------ UPDATE 1 -------
I have updated my code example to make it more specific.
Know that, in my real COBOL program, there are various occurences of SEARCH-ABORT and STORAGE-ABORT possibilities (I am working with many arrays).
I want to make my code as good as possible, hence my will to access the current paragraph name instead of having to write it.
Thank you again.
------- UPDATE 2 ------
Well then. It seems I cannot do it (the users of my program will probably reject any debug messages they are not used to get - For your information, I am rewriting a 50 years old program with very, very bad programming practices such as upward GO TOs, fall-through logic and the godforsaken ALTER, and I want to get the same output at the end).
Don't worry, I will not cry tonight. This was just an esthetical improvement to my code, and I can live without it (my code is already a lot prettier than what I based myself on).
I thank all of you for your time, and wish you a good... Stack Overday !
As Simon Sobisch has correctly indicated in his answer, the only way to do exactly what you want is to use the "debugging declaratives". See later in the answer for making that work, but no-one should allow you to do this to a Production program.
COBOL is a compiled language so there is no no automatic access to any data-name or procedure name (paragraph or SECTION) unless the compiler makes something available. Which, excluding the case above, it doesn't.
That leaves three approaches: doing it manually (which you correctly want to avoid, as sure as peaches someone is going to copy or relocate code without changing the literal); pre-processing (with a program or the editor) to automatically populate your field with the correct label; doing something else.
Since you are implicitly discounting the first, again I believe correctly, let's consider the second. What if you have two, three or eight things in the same paragraph/SECTION which are all "business errors" (although usually these types of things are more "integrity errors", a state which should not exist, so don't continue)?
Since you will get those, a "pre-processing" solution starts to get more ugly.
What else can be done?
Well, it's something we've faced for many, many years. The answer is, unique (within the program) error numbers. The individual errors can be named, well, and given a number. The well-named error reference is difficult to use "incorrectly". When adding a new error, it is difficult to duplicate an existing number. Or, to put it another way, it is easy to duplicate but horribly easy to spot in testing - "hey, that's produced 1234, that's wrong".
It's in no way bullet-proof, but the data-name (and any associated text) give better indication of the problem than a paragraph-name (which is not going to be, except artificially, any indication of what the error is, just the location of it). The error references are very easy to find in the program, and from that it is easy to locate the procedure name, except you don't actually need it any more.
Whether the program with error-numbers outweigh the dross of manually maintained MOVE 'literal' TO some-standard-name programs is unknown. But you can guess which I favour and recommend.
Now, how to do it for Enterprise COBOL with DECLARATIVES.
IDENTIFICATION DIVISION.
PROGRAM-ID. STAB39.
ENVIRONMENT DIVISION.
CONFIGURATION SECTION.
SOURCE-COMPUTER. FRED DEBUGGING MODE.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 W-WHEN-COMPILED PIC X(8)BX(8).
01 ABT-LOC PIC X(30).
PROCEDURE DIVISION.
DDECLARATIVES.
DSOME-SECTION SECTION.
D USE FOR DEBUGGING ON ALL PROCEDURES
D .
DSOME-PARA.
D MOVE DEBUG-NAME TO ABT-LOC
D .
DEND DECLARATIVES.
STARTING-UP SECTION.
DISPLAY
ABT-LOC
D DISPLAY
D "IT IS STARTING UP"
MOVE WHEN-COMPILED TO W-WHEN-COMPILED
DISPLAY
"STAB39 "
W-WHEN-COMPILED
.
A-PARA.
DISPLAY
ABT-LOC
PERFORM
10 TIMES
D DISPLAY
"ITERATING"
END-PERFORM
.
ANOTHER-PARA.
DISPLAY
ABT-LOC
PERFORM THE-PARA
10 TIMES
PERFORM THE-SECOND-PARA
GOBACK
.
THE-PARA.
DISPLAY
ABT-LOC
.
THE-SECOND-PARA.
DISPLAY
ABT-LOC
.
Some notes:
The SOURCE-COMPUTER paragraph is required to use COBOLs in-built debugging features, to turn them on. So the ENVIRONMENT DIVISION and CONFIGURATION SECTION are also required. The "computer name", FRED in the example, is required, but it is irrelevant. You can "name" your computer after your favourite pet or relative if you like, or put anything there, there just has to be something.
DECLARATIVES can only be specified at the start of the PROCEDURE DIVISION. They must be within a SECTION and all actions must be within a paragraph belonging to a SECTION. The names of the SECTION and paragraph are irrelevant, but make them meaningful anyway.
Because the DECLARATIVES must contain a SECTION, you will be subject to an informational diagnostic message if your first procedure label is not also a SECTION. This does not require using SECTIONS over paragraphs in your program, it has no further effect.
The D in column seven indicates a "debugging line". These lines only get code generated when you turn debugging on with the SOURCE-COMPUTER paragraph.
The program exercises all use of a paragraph (and use of a SECTION is no different for this example) except GO TO. Paragraphs which are GO TO'd will produce the same results as any other reference, but you won't see GO TOs in my programs :-)
It is possible to name the procedure or procedures you want to "trap" with the DECLARATIVES instead of using "ALL PROCEDURES".
You may have multiple DEBUGGING procedures, and you can include extensive code within them if you wish (setting up conditions for testing, for instance).
Although this feature has existed in COBOL for a long time, it is probably fair to say that it is not widely used, especially as specific "debugging products" became available.
It is not enough just to have this program, the "run time" needs to have DEBUG turned on, if it is not the default. The run-time on z/OS is called Language Environment and is shared by multiple languages (allowing easy inter-language communication). Languages include C/C++, PL/I and Java as well as COBOL. There are Language Environment routines and macros available to make HLASM/Assembler programs "LE Compliant" to also provide ready interfacing.
To see what run-time options your site has as default, the easiest thing to do is to include a CEEOPTS DD statement in your run JCL.
//CEEOPTS DD *
RPTOPTS(ON)
This will list out all the options used for your "Enclave" (your run environment) and indicate where each option is sourced from.
If, in the OPTION column, you see NODEBUG, then COBOL debugging is turned off by default. To turn it on for a particular run:
//CEEOPTS DD *
DEBUG
This will allow all the D-labelled debugging lines and the debugging DECLARATIVES to execute.
This will do what you want, but no-one will allow a program with debugging on into Production, so you can't use it for what you want.
In order of preference, I advise error-numbers (and testing), automation, hand-coded procedure-name literals.
IBM fully documents all its products, and you can find the documentation (Language Reference and Programming Guide amongst others) for Enterprise COBOL V4.2 and also Language Environment (several) for your release of z/OS.
One final point. Don't use GO TO to "break out" of your normal processing flow. Use PERFORM. Even when, logically, the PERFORM cannot return. Using GO TO will turn off compiler optimisation for paragraphs/SECTIONs containing the GO TO which can easily cause a noticeable impact on execution. This is the reverse of the advice from before IBM COBOL ensured that the state of PERFORMed paragraphs/SECTIONs is not preserved between CALLs. At that time the correct advice was to use GO TO. It is no longer the correct advice.
As you have the pseudo-code "something bad happened here" I assume an exception. In this case the standard (COBOL 2002, COBOL 2014) function EXCEPTION-LOCATION may help (although the actual string is implementor-defined I assume the paragraph may be in there [GnuCOBOL for example has the format: program-id; paragraph [or paragraph OF section or section, depending on your program]; source-line]).
If your COBOL compiler provides this information in this function and there is no exception in the offending part already: create one via subtract 1 from unsigned-var or similar.
As Bill already said (or implied): this is a question where the actual COBOL compiler used will be the most important part if you must have the names in as identifier and as label or not.
Edit (after the actual COBOL compiler is known):
IBM MVS Enterprise COBOL doesn't have the EXCEPTION-LOCATION function. Therefore I see only one built-in solution:
DECLARATIVES.
debug-declaratives SECTION.
USE FOR DEBUGGING ON ALL PROCEDURES.
debug-par.
MOVE debug-name TO current-procedure.
END DECLARATIVES.
But as this is only active if your program runs in debugging-mode (which may causes a lot of debugging messages to occur) I don't suggest to actual use this.
Try to use an Editor providing macros (or run a shell script on your actual source) to create the source you pass to the compiler afterwards.
I am responsible for converting an old UNIX based COBOL batch application that was developed by a consultant back in the 1990s to a Windows environment but still in COBOL using Microfocus (Eclipse, etc).
This is a pretty straight-forward task except for one little glitch.
The old application never did any explicit file handling within the COBOL. That is there are no FDs, OPENs, READs, WRITEs or CLOSE commands in the COBOL programs. Instead they wrote a C program that would do one of those different functions based on parameters passed to it (including, but not limited to file name, rec length, and the function desired.)
I would like to rewrite that subroutine in COBOL, which would require very little modifications to the COBOL main programs being converted. That is, it would still call that subroutine, but it would now be in COBOL instead of C.
But the challenge is how to write that subroutine so that it is able to act on most any file. I would think I have to go the route of variable length records because they could literally be any length up to to-be-determined maximum size, but seems like it would be vulnerable to error (as it tries to open different types of files).
Does anybody have any experience on this or ideas on a task like this? If not,l I may have to go the blunt force route of replacing each call statement to that subroutine with the specific COBOL command (Open, Read, etc) that needs to be performed and obviously FD and SELECT for every file would need to be added to the main program.
Thanks in advance.
You might be able to
CALL "subprogram" USING fd-name
where fd-name is
FD fd-name.
...
So, yes? maybe?, you might be able to pull off a subprogram that can take generic COBOL files. But, then you get into matching record layouts and other fun things, so, be wary. This might not work COBOL to COBOL, but it does work COBOL to C and back, as you end up passing a reference to the file control block.
You'll likely be better off looking into stock system libraries. Things like CBL_OPEN_FILE and CBL_READ_FILE if they are available. This will give you a much closer match to streaming IO that will be assumed in the current C subprogram.
Or, as Bill is suggesting in the comments, try and figure out why C was used and if you don't want the foreign functions, just dig in and write new COBOL procedures, as that will likely read better in the end.
My question is pertaining to a file status 23, which according to MicroFocus means that upon my attempt to READ from a .DAT file:
"Indicates no record found."
or
"Indicates a duplicate key condition. Attempt has been made to store a
record that would create a duplicate key in the indexed or relative
file or a duplicate alternate record key that does not allow
duplicates."
I have eliminated the fact that the latter is my issue because I'm allowing duplicates in this case.
The reason I'm stumped is that I'm using a START to navigate to the record inside of my .DAT file, and when I execute a READ just after the START has positioned my file pointer, I get the file status 23.
Here is my code:
900-GET-INST-ID.
OPEN INPUT INST-MST.
MOVE FALL-IN-INST TO INST-NAME-REC.
START INST-MST
KEY EQUAL TO INST-NAME-REC
INVALID KEY
DISPLAY "RECORD NOT FOUND"
NOT INVALID KEY
READ INST-MST
MOVE INST-ID-REC TO WS-INST-ID
END-START.
CLOSE INST-MST.
So when I am running this code my START successfully runs and goes into the NOT INVALID KEY block, and then the very next line executes and my read is null. How can this be if my alternate key (INST-NAME-REC) is actually found inside the .DAT?
I have ensured that my FD picture clauses match exactly in the ISAM Build program and in this program (the reading program).
The second reason you show is excluded not because you allow duplicate keys, but because that error message with that file-status is for a WRITE, and your failure is on a READ.
Here's your problem:
READ INST-MST
Here's how you fix it:
READ INST-MST NEXT
In COBOL 85, the READ statement has two formats. Format 1 is for a sequential read and Format 2 is for a keyed (random) read.
Unfortunately, the minimum READ syntax for both sequential and keyed reads is:
READ file-name
Which means if you use READ file-name the compiler will implicitly treat it as Format 1 or Format 2 depending on your SELECT statement.
READ file-name NEXT RECORD is identical to READ file-name NEXT.
Consult your actual documentation for a full explanation and discovery of possible Language Extensions from the vendor. If you consult closely, the behaviour of READ file-name with no further option depends on the type of file. With a keyed file, the default is a keyed READ. You key field (luckily) does not contain a key that exists, so you get the 23.
Even if it didn't work like that, what would be the point of not using the word NEXT? The compiler always knows what you tell it (which sometimes is not what you think you tell it), but in a situation like this, the human reader can be very unsure. The last thing you want to do when bug-hunting is break off to look at the manual to discover exactly how that behaves, and then try to work it if that behaviour was the one sought by the original coder. The bug? A bug? Intended, but sloppy, code? No-one wants to spend that time, and look, even now, it is you.
A couple of comments on your code.
Look up the FILE STATUS clause of the SELECT. Use it. One field per file. Check after each IO. It'll save you grief.
Once using the FILE STATUS, ditch the imperative parts of the IO statements (the something/NOT something) and replace by tests of the file-status field (using 88s).
It looks like you are OPENing and CLOSEing your look-up file all the time. Please don't. OPEN and CLOSE can be very heavy and time-consuming, so do them once per program per file. If you've done that because of a problem, find a correct resolution to that problem, don't use a hack.
Drop the full-stops/periods except where they are needed. This is COBOL 85, which means for 30 years the number of full-stops/periods required in the PROCEDURE DIVISION have been greatly reduced. Get modern, and take advantage of that, it'll save you Gotcha!s as you copy/paste code, leaving the one which shouldn't be there and changing the way the program behaves.
I'm developing an application that parses Cobol programs. In these programs some respect the traditional coding style (programm text from column 8 to 72), and some are newer and don't follow this style.
In my application I need to determine the coding style in order to know if I should parse content after column 72.
I've been able to determine if the program start at column 1 or 8, but prog that start at column 1 can also follow the rule of comments after column 72.
So I'm trying to find rules that will allow me to determine if texts after column 72 are comments or valid code.
I've find some but it's hard to tell if it will work everytime :
dot after column 72, determine the end of sentence but I fear that dot can be in comments too
find the close character of a statement after column 72 : " ' ) }
look for char at columns 71 - 72 - 73, if there is not space then find the whole word, and check if it's a key word or a var. Problem, it can be a var from a COPY or a replacement etc...
I'd like to know what do you think of these rules and if you have any ideas to help me determine the coding style of a Cobol program.
I don't need an API or something just solid rules that I will be able to rely on.
I think you need to know the COBOL compiler for each program. Its documentation should tell you what conventions/configurations/switches it uses to decide if the source code ends at column 72 or not.
So.... which compiler(s)?
And if you think the column 72 issue is a pain, wait till you get around to actually parsing the COBOL itself. If you are not well prepared to handle the lexical issues of the language, you are probably very badly prepared to handle the syntactic ones.
There is no absolutely reliable way to determine if a COBOL program
is in fixed or free format based only on the source code. Heck it is sometimes difficult to identify
the programming language based only on source code. Check out
this classic polyglot - it is valid under 8 different language compilers. That
said, you could try a few heuristics that might yield
the correct answer more often than not.
Compiler directives imbedded in source code
Watch for certain compiler directives that determine code format.
Unfortunately, every compiler vendor uses their own flavour of directive.
For example, Microfocus COBOL uses the
SOURCEFORMAT directive. This directive will appear near the top of the program so a short pre-scan
could be used to find it. On the other hand, OpenCobol uses >>SOURCE FORMAT IS FREE and
>>SOURCE FORMAT IS FIXED to toggle between free and fixed format, different parts of the same program
could be formatted differently!
The bottom line here is that you will have to support the conventions of multiple COBOL compilers.
Compiler switches
Source code format can be also be specified using a compiler switch. In this case, there are no concrete
clues to go on. However, you can be reasonably sure that the entire source program will be either
fixed or free. All you can do here is guess. Unless the programmer is out to "mess with
your head" (and some will), a program in free format will have the keywords IDENTIFICATION DIVISION or ID DIVISION, starting before column 8.
Every COBOL program will begin with these keywords so you can use them as the anchor point for determining code format in the
absence of imbedded compiler directives.
Warning - this is far from fool proof, but might be a good start.
There won't be an algorithm to do this with 100% certainty, because if comments can be anything, they can also be compilable COBOL code. So you could theoretically write a program that means one thing if the comments are ignored, and something else entirely if the comments are treated as part of the COBOL.
But that's extremely unlikely. What's most likely to happen is that if you try to compile the code under the wrong convention, it will simply fail. So the only accurate way to do this is to try compiling/parsing the program one way, and if you come to a line that can't make sense, switch to the other style. You could also support passing an argument to the compiler when the style is already known.
You can try using heuristics like what you've described, but that will never be totally accurate. The most they can give you is a probability that the code is one or the other style, which will increase as they examine more and more lines of code. They could be useful for helping you guess the style before you start compiling, or for figuring out when the problem is really just a typo in the code.
EDIT:
Regarding ideas for heuristics, it's hard to say. If there were a standard comment sigil like // or # in other languages, this would be a lot easier (actually, there is, but it sounds like your code doesn't follow this convention). The only thing I can think of would be to check whether every line (or maybe 99% of lines, and not counting empty lines or lines commented with *) has a period somewhere before position 72.
One thing you DON'T want to do is apply any heuristics to the part after position 72. That is, you don't want to be checking the comments to see if they're valid COBOL. You want to check what you know is COBOL first, and see if that works by itself. There are several reasons for this:
Comments written in English are likely to have periods and quotes in them, so your first and second bullet points are out.
Natural languages are WAY harder to parse than something like COBOL.
The comments could easily have COBOL in them (maybe someone commented out the previous version of the line).
An important rule for comments is that they should never affect what the program does. If changing the comments can change how the program is compiled, you violate that.
All that in mind, my opinion is that you shouldn't use heuristics at all. You should always try to compile the program under both conventions unless one is explicitly specified. There's a chance that code will compile successfully under both conventions, and then you'll have two different programs and no way to tell which one is correct.
If that happens, you need to compare the two results (perhaps with a hash or something) to see if they're the same program. If they're the same, great, but if not, you'll need to force the user to explicitly choose a convention.
Most COBOL compilers will allow you to generate and analyze the post text manipulation phase.
The text preprocessor output can be seen (using OpenCOBOL for the example)
cobc -E program.cob
The text manipulation processor deals with any COPY ... REPLACING compiler directives, as well as converting SOURCE FORMAT IS FIXED (with line continuations, string literal concatenations, comment line removal, among other things) to the actual free format that the compiler lexical analyzer needs. A lot of the OpenCOBOL toolkits (Cross referencer and Animator, to name two) use source code AFTER the preprocessor pass. I don't think you'll lose any street cred if your parser program relies on post processed source code files.
I suspect that the syntax diagram for a plsql_block as given in the
Oracle® Database PL/SQL Language Reference for Relese 2 is wrong.
(For reference, here's the current link to that document)
The following piece of PL/SQL compiles fine:
declare
cursor
cursor_definition
is select * from dual;
variable_declaration number;
begin
null;
end;
The following statements are assumptions that I make based on the piece of PL/SQL above and based on Oracle's syntax diagram.
The declare section (above) consists of a cursor definition followed by a variable declaration (which in turn is an item declaration).
An item declaration can only be an element of an item list 1.
A cursor definition can only be an element of an item list 2.
An item list 2 can never be followed by an item list 1.
Now, the variable declaration following the cursor definition contradicts point 4. Therefore I conclude that the
syntax diagram is wrong.
Maybe I am overlooking something, in which case I'd be very grateful for pointing this out to me.
Please understand that a wrong syntax diagram per se is no big deal to me. But I am in the process of writing a PL/SQL parser
and the parser stumbles for the exact situation given with the example PL/SQL code. So, in order to improve the parser, I'd like
to have a more authorative sequence diagram.
I concur. The syntax diagrams explicitly state that a plsql_block is effectively item_list_2 preceded by an optional item_list_1.
Further, cursor definitions (with the is bit) can only occur in item_list_2 and variable declarations (with or without an =) are part of the item_declaration set and can therefore only be in item_list_1.
Those facts make your code sample incorrect so, if it manages to compile, then either:
the syntax diagrams are wrong; or
the compiler doesn't follow them to the letter; or
your looking at code that's covered by different syntax diagrams.
On that last bullet point, interestingly enough, the syntax diagrams for 11.1 are slightly different.
The declare section can be item_list_1 or item_list_2 or item_list_1 followed by item_list_2.
Where it gets interesting is that item_list_1 can have any number of item_declaration entries and this includes both variable_declaration and cursor_declaration.
In 11.1, a cursor_declaration can be either a declaration or a definition, based on the language elements in 11.2 (in other words, there is no cursor_definition type since the declaration allows both in the declaration).
So what you have is perfectly valid in 11.1 so the first thing I'd check is that you're actually running 11.2 where that successful compilation is taking place.
It's still possible of course that you're running 11.2 and the syntax diagrams are wrong, in which case you should complain bitterly to Oracle but I don't know what sort of a response you'll get from a company whose flagship database product can't tell the difference between an empty varchar and a NULL (a).
(a) I'll never pass up an opportunity to mention this and advance the cause of my beloved DB2 :-)