Null References¶
Hoare, T. (2009). Null References: The Billion Dollar Mistake.
Retired. This entry was not a citation. Our extractor stored an inline prose definition from the article as though it were a bibliographic record: the title names a concept rather than a published work, and the citation text names no work at all. The page is kept because links to it still resolve, but it is withdrawn from the reference list. This entry is kept so the citations that pointed at it still resolve, and so the correction is visible rather than silent.
Cited by¶
3 citations across 3 artifacts.
Each citation links to the sentence it supports in the citing article.
Primes¶
- Empty Set
- In programming it is the empty list, array, or map; the typed
None/Nothingof Option/Maybe types; theVoidandUnittypes; and the sharp contrast between an untypednull(danger) and a typedNothing(safety).This sourceIdentifies the conflation of typed empty with untyped null as a foundational error, motivating Option/Maybe types (typed `None`/`Nothing`) that keep operations total.
- In programming it is the empty list, array, or map; the typed
- Unverified Precondition
- Software. Null dereference and use-after-free: a reference is used without checking it points to a live object, so the program crashes or proceeds with corrupted state — the canonical computing case.
This sourceHoare's account of inventing the null reference and its consequence — the null dereference, the canonical computing case of using a reference without checking it points to a live object.
- Software. Null dereference and use-after-free: a reference is used without checking it points to a live object, so the program crashes or proceeds with corrupted state — the canonical computing case.
Mechanisms¶
- Empty Collection Return
- A codebase that guarantees empty-not-null never suffers the null-reference dereference that Tony Hoare famously called his "billion-dollar mistake."
This sourceRecords Tony Hoare’s characterization of introducing null references as his “billion-dollar mistake.”
- A codebase that guarantees empty-not-null never suffers the null-reference dereference that Tony Hoare famously called his "billion-dollar mistake."
Verification¶
Does it exist? Not checked yet. This entry carries no identifier to resolve. It was extracted from the citation as written in the article, normalized, and deduplicated against the rest of the registry.
Does it back the claim? Not recorded. Neither this nor any other of the 3 citations of this work carries a recorded support check.
Was it audited? Yes. A second, independent pass read the citation against the article text and recorded a verdict.
Support is checked per citation rather than per work — the same source can be cited soundly in one article and wrongly in another. Per-citation recording began recently, so a citation with no recorded check is a gap in the record rather than evidence it went unchecked.
See how references were verified.
Links previously used in the corpus¶
Before the registry existed this work was also linked 2 other ways.
- https://www.infoq.com/presentations/Null-References-The-Billion-Dollar-Mistake-Tony-Hoare/ ×2
- https://qconlondon.com/london-2009/qconlondon.com/london-2009/presentation/Null%2BReferences_%2BThe%2BBillion%2BDollar%2BMistake.html ×1
Registry ID ref:acb491486b61 · see in the full table