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Limitations of the PL/SQL Wrap Utility

Limitations of the PL/SQL Wrap Utility

Although wrapping a compilation unit helps to hide the algorithm and makes reverse-engineering hard, Oracle Corporation does not recommend it as a secure method for hiding passwords or table names.

Because the source code is parsed by the PL/SQL compiler, not by SQL*Plus, you cannot include substitution variables using the SQL*Plus DEFINE notation inside the PL/SQL code. You can use substitution variables in other SQL statements that are not obfuscated.

The wrap utility does not obfuscate the source code for triggers. To hide the workings of a trigger, you can write a one-line trigger that calls a wrapped procedure.

Some, but not all, comments are removed in wrapped files.

If your PL/SQL compilation units contain syntax errors, the wrap utility detects and reports them. The wrap utility does not detect semantic errors, such as tables or views that do not exist. Those errors are detected when you run the output file in SQL*Plus.

The Wrap Utility is upward-compatible between Oracle releases, but is not downward-compatible. For example, you can load files processed by the V8.1.5 wrap utility into a V8.1.6 Oracle database, but you cannot load files processed by the V8.1.6 wrap utility into a V8.1.5 Oracle database.

Obfuscating Source Code with the PL/SQL Wrap Utility C-3

Limitations of the PL/SQL Wrap Utility

C-4 PL/SQL User's Guide and Reference

D

How PL/SQL Resolves Identifier Names

This appendix explains how PL/SQL resolves references to names in potentially ambiguous SQL and procedural statements.

This appendix contains these topics:

What Is Name Resolution? on page D-1

Examples of Qualified Names and Dot Notation on page D-2

Differences in Name Resolution Between SQL and PL/SQL on page D-3

Understanding Capture on page D-3

Avoiding Inner Capture in DML Statements on page D-4

Qualifying References to Object Attributes and Methods on page D-5

Calling Parameterless Subprograms and Methods on page D-5

Name Resolution for SQL Versus PL/SQL on page D-6

What Is Name Resolution?

During compilation, the PL/SQL compiler determines which objects are associated with each name in a PL/SQL subprogram. A name might refer to a local variable, a table, a package, a procedure, a schema, and so on. When a subprogram is recompiled, that association might change if objects have been created or deleted.

A declaration or definition in an inner scope can hide another in an outer scope. In the following example, the declaration of variable client hides the definition of datatype Client because PL/SQL names are not case sensitive:

BEGIN <<block1>> DECLARE

TYPE Client IS RECORD (...); TYPE Customer IS RECORD (...);

BEGIN

 

 

 

DECLARE

 

 

 

client Customer;

--

hides definition of type Client

 

 

--

in outer scope

lead1

Client;

--

not allowed; Client resolves to the

 

 

--

variable client

lead2

block1.Client; --

OK; refers to type Client

BEGIN

 

 

 

NULL;

 

 

 

END;

 

 

 

How PL/SQL Resolves Identifier Names D-1

Examples of Qualified Names and Dot Notation

END;

END;

You can still refer to datatype Client by qualifying the reference with block label block1.

In the following set of CREATE TYPE statements, the second statement generates an error. Creating an attribute named MANAGER hides the type named MANAGER, so the declaration of the second attribute does not work.

CREATE TYPE manager AS OBJECT (dept NUMBER);

/

CREATE TYPE person AS OBJECT (manager NUMBER, mgr manager);

/

Examples of Qualified Names and Dot Notation

During name resolution, the compiler can encounter various forms of references including simple unqualified names, dot-separated chains of identifiers, indexed components of a collection, and so on. For example:

CREATE PACKAGE pkg1 AS m NUMBER;

TYPE t1 IS RECORD (a NUMBER); v1 t1;

TYPE t2 IS TABLE OF t1 INDEX BY BINARY_INTEGER; v2 t2;

FUNCTION f1 (p1 NUMBER) RETURN t1; FUNCTION f2 (q1 NUMBER) RETURN t2;

END pkg1;

CREATE PACKAGE BODY pkg1 AS

FUNCTION f1 (p1 NUMBER) RETURN t1 IS

n NUMBER;

 

 

BEGIN

 

 

n := m;

-- (1)

unqualified name

n := pkg1.m;

-- (2)

dot-separated chain of identifiers

 

--

(package name used as scope

 

--

qualifier followed by variable name)

n := pkg1.f1.p1;

-- (3)

dot-separated chain of identifiers

 

--

(package name used as scope

 

--

qualifier followed by function name

 

--

also used as scope qualifier

 

--

followed by parameter name)

n := v1.a;

-- (4)

dot-separated chain of identifiers

 

--

(variable name followed by

 

--

component selector)

n := pkg1.v1.a;

-- (5)

dot-separated chain of identifiers

 

--

(package name used as scope

 

--

qualifier followed by

 

--

variable name followed by component

 

--

selector)

n := v2(10).a;

-- (6)

indexed name followed by component

 

--

selector

n := f1(10).a;

-- (7)

function call followed by component

 

--

selector

n := f2(10)(10).a; -- (8)

function call followed by indexing

 

--

followed by component selector

n := scott.pkg1.f2(10)(10).a;

 

-- (9)

function call (which is a dot-

D-2 PL/SQL User's Guide and Reference

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