Object Lifetime and Null Handles

Overview

Most null-handle crashes are ownership bugs: one branch skips construction while downstream code assumes construction always happened.

In one regression, a sequence builder created packets in 99% of seeds, then skipped construction in a timeout-recovery branch. The fatal showed up much later in a scoreboard callback, so the stack trace blamed the wrong component for hours.\n\nThe reliable fix was to define a single owner responsible for object creation and to assert non-null at handoff boundaries. Debug gets easier when every component either guarantees construction or explicitly treats null as part of the contract.

In this topic

1. Concept Explained
2. Code Examples
3. SystemVerilog vs C++/Java
4. Pitfalls
5. Exercises
6. Interview Questions

Read the concept first, study the code examples, compare against C++/Java, then test yourself with the exercises and interview questions.

OOP bug root-cause decision tree

ROOT CAUSE TREE FOR OOP FAILURES

symptom: test behavior mismatch
                 |
           reproducible?
            /       \
          no         yes
          |           |
   check race/time   inspect object state
                      /        |        \
                 null handle  aliasing  wrong override
                    |            |           |
               construct path  clone policy  virtual+factory map
                    \           |           /
                     +------ implement fix ------+

Localize the failing object lifecycle before broad refactoring.

Related topics

• Tricky Pitfalls & Debug section

• SystemVerilog OOP Mastery hub