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We present lambda_sym, a typed λ-calculus forlenient symbolic execution, where some language constructs do not recognize symbolic values. Its type system, however, ensures safe behavior of all symbolic values in a program. Our calculus extends a base occurrence typing system with symbolic types and mutable state, making it a suitable model for both functional and imperative symbolically executed languages. Naively allowing mutation in this mixed setting introduces soundness issues, however, so we further addconcreteness polymorphism, which restores soundness without rejecting too many valid programs. To show that our calculus is a useful model for a real language, we implemented Typed Rosette, a typed extension of the solver-aided Rosette language. We evaluate Typed Rosette by porting a large code base, demonstrating that our type system accommodates a wide variety of symbolically executed programs.
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Strongly bounded termination with applications to security and hardware synthesis
Termination checking is a classic static analysis, and, within this focus, there are type-based approaches that formalize termination analysis as type systems (i.e., so that all well-typed programs terminate). But there are situations where a stronger termination property (which we call strongly-bounded termination) must be determined and, accordingly, we explore this property via a variant of the simply-typed λ-calculus called the bounded-time λ-calculus (BTC). This paper presents the BTC and its semantics and metatheory through a Coq formalization. Important examples (e.g., hardware synthesis from functional languages and detection of covert timing channels) motivating strongly-bounded termination and BTC are described as well.
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- PAR ID:
- 10194348
- Date Published:
- Journal Name:
- Proceedings of the 5th ACM SIGPLAN International Workshop on Type-Driven Development
- Page Range / eLocation ID:
- 1 to 10
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1145/3406089.3409029
