Compile-Time Warnings

Compile-time warnings can greatly improve the maintainability of your code and reduce the chance that bugs will creep into it. Compile-time warnings differ from compile-time errors; with warnings, your program will still compile and run. You may, however, encounter unexpected behavior or reduced performance as a result of running code that is flagged with warnings.

This section explores how compile-time warnings work and which issues are currently detected. Let’s start with a quick example of applying compile-time warnings in your session.

A Quick Example

A very useful compile-time warning is PLW-06002: Unreachable code. Consider the following program (available in the cantgothere.sql file on the book’s web site). Because I have initialized the salary variable to 10,000, the conditional statement will always send me to line 9. Line 7 will never be executed.

      /* File on web: cantgothere.sql */
 1    PROCEDURE cant_go_there
 2    AS
 3       l_salary NUMBER := 10000;
 4    BEGIN
 5       IF l_salary > 20000
 6       THEN
 7          DBMS_OUTPUT.put_line ('Executive');
 8       ELSE
 9          DBMS_OUTPUT.put_line ('Rest of Us');
10       END IF;
11     END cant_go_there;

If I compile this code in any release prior to Oracle Database 10g, I am simply told “Procedure created.” If, however, I have enabled compile-time warnings in my session on the new release and then try to compile the procedure, I get this response from the compiler:

SP2-0804: Procedure created with compilation warnings


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