PL/SQL User’s Guide and Reference (10.2): “4 Using PL/SQL Control Structures – Using the NULL Statement”
“…Note that the use of the NULL statement might raise an unreachable code warning if warnings are enabled.”
Example 4-23 Using NULL as a Placeholder When Creating a Subprogram
CREATE OR REPLACE PROCEDURE award_bonus (emp_id NUMBER, bonus NUMBER) AS
BEGIN — executable part starts here
NULL; — use NULL as placeholder, raises “unreachable code” if warnings enabled
Indeed, when I compile the above in 10.2 with PL/SQL warnings on, I get PLW-06002 as expected (due to bug 3680132 I get “Message 6002 not found; No message file for product=plsql, facility=PLW” but at least I can look it up in the reference).
“PLW-06002: Unreachable code”
“Cause: Static program analysis determined that some code on the specified line would never be reached during execution.”
I agree that a PL/SQL warning would be desirable in the case where a procedure has nothing but a NULL in it (probably a stub). Correct me if I’m wrong, but if I were to call award_bonus, surely the NULL is “executed” – therefore, it is reachable! A more appropriate warning would be something like “function/procedure does nothing”, or “get back to work you silly mug, you’ve forgotten to finish the code”. Maybe they just couldn’t be bothered making up another warning code.