Granullar: gradual nullable types for Java

Brotherston, Dan; Dietl, Werner; Lhoták, Ondřej

doi:10.1145/3033019.3033032

Cited by 7 publications

(4 citation statements)

References 12 publications

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“…6.4.3 Gradual Nullable Type Systems. Brotherston et al [2017] present Granullar, a gradual pluggable type system for Java. The type system ensures that NullPointerExceptions cannot occur within checked code; only on the boundary between checked and unchecked code.…”

Section: Nullable Type Systemsmentioning

confidence: 99%

Relational nullable types with Boolean unification

Madsen

Pol

2021

Proc. ACM Program. Lang.

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We present a simple, practical, and expressive relational nullable type system. A relational nullable type system captures whether an expression may evaluate to null based on its type, but also based on the type of other related expressions. The type system extends the Hindley-Milner type system with Boolean constraints, supports parametric polymorphism, and preserves principal types modulo Boolean equivalence. We show how to support full Hindley-Milner style type inference with an extension of Algorithm W. We conduct a preliminary study of open source projects showing that there is a need for relational nullable type systems across a wide range of programming languages. The most important findings from the study are: (i) programmers use programming patterns where the nullability of one expression depends on the nullability of other related expressions, (ii) such invariants are commonly enforced with run-time exceptions, and (iii) reasoning about these programming patterns requires not only knowledge of when an expression may evaluate to null, but also when it may evaluate to a non-null value. We incorporate these observations in the design of the proposed relational nullable type system.

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Section: Nullable Type Systemsmentioning

confidence: 99%

Relational nullable types with Boolean unification

Madsen

Pol

2021

Proc. ACM Program. Lang.

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“…We ran the Index Checker on three open-source Java projects (table 4.3) used previously to evaluate bug-finding and verification tools [76,144,56]. Our goal was either to verify that each was free of array indexing bugs, or to find and fix all their array indexing bugs.…”

Section: Case Studies Of the Index Checkermentioning

confidence: 99%

Lightweight verification via specialized typecheckers

Kellogg

2021

Proceedings of the 29th ACM Joint Meeting on European Software Engineering Conference and Symposium on the Foundations of Softw

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“…Granullar [20] inserts runtime checks at the unannotated code boundary to guarantee soundness of checked code annotations. We did not investigate this approach due to potential runtime overhead and the riskiness of shipping modified code.…”

Section: Handling Unannotated Codementioning

confidence: 99%

NullAway: practical type-based null safety for Java

Banerjee

Clapp

Sridharan

2019

Proceedings of the 2019 27th ACM Joint Meeting on European Software Engineering Conference and Symposium on the Foundations of

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NullPointerExceptions (NPEs) are a key source of crashes in modern Java programs. Previous work has shown how such errors can be prevented at compile time via code annotations and pluggable type checking. However, such systems have been difficult to deploy on large-scale software projects, due to significant build-time overhead and / or a high annotation burden. This paper presents NullAway, a new type-based null safety checker for Java that overcomes these issues. NullAway has been carefully engineered for low overhead, so it can run as part of every build. Further, NullAway reduces annotation burden through targeted unsound assumptions, aiming for no false negatives in practice on checked code. Our evaluation shows that NullAway has significantly lower build-time overhead (1.15×) than comparable tools (2.8-5.1×). Further, on a corpus of production crash data for widely-used Android apps built with NullAway, remaining NPEs were due to unchecked third-party libraries (64%), deliberate error suppressions (17%), or reflection and other forms of post-checking code modification (17%), never due to NullAway's unsound assumptions for checked code. CCS CONCEPTS• Software and its engineering → Extensible languages; Compilers; Formal software verification.

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Granullar: gradual nullable types for Java

Cited by 7 publications

References 12 publications

Relational nullable types with Boolean unification

Relational nullable types with Boolean unification

Lightweight verification via specialized typecheckers

NullAway: practical type-based null safety for Java

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