We present a method for example-guided synthesis of functional programs over recursive data structures. Given a set of input-output examples, our method synthesizes a program in a functional language with higher-order combinators like map and fold. The synthesized program is guaranteed to be the simplest program in the language to fit the examples.Our approach combines three technical ideas: inductive generalization, deduction, and enumerative search. First, we generalize the input-output examples into hypotheses about the structure of the target program. For each hypothesis, we use deduction to infer new input/output examples for the missing subexpressions. This leads to a new subproblem where the goal is to synthesize expressions within each hypothesis. Since not every hypothesis can be realized into a program that fits the examples, we use a combination of best-first enumeration and deduction to search for a hypothesis that meets our needs.We have implemented our method in a tool called λ 2 , and we evaluate this tool on a large set of synthesis problems involving lists, trees, and nested data structures. The experiments demonstrate the scalability and broad scope of λ 2 . A highlight is the synthesis of a program believed to be the world's earliest functional pearl.

We present Apposcopy, a new semantics-based approach for identifying a prevalent class of Android malware that steals private user information. Apposcopy incorporates (i) a highlevel language for specifying signatures that describe semantic characteristics of malware families and (ii) a static analysis for deciding if a given application matches a malware signature. The signature matching algorithm of Apposcopy uses a combination of static taint analysis and a new form of program representation called Inter-Component Call Graph to efficiently detect Android applications that have certain control-and data-flow properties. We have evaluated Apposcopy on a corpus of real-world Android applications and show that it can effectively and reliably pinpoint malicious applications that belong to certain malware families.

This paper presents a new technique for automatically synthesizing SQL queries from natural language (NL). At the core of our technique is a new NL-based program synthesis methodology that combines semantic parsing techniques from the NLP community with type-directed program synthesis and automated program repair. Starting with a program sketch obtained using standard parsing techniques, our approach involves an iterative refinement loop that alternates between quantitative type inhabitation and automated sketch repair. We use the proposed idea to build an end-to-end system called Sqlizer that can synthesize SQL queries from natural language. Our method is fully automated, works for any database without requiring additional customization, and does not require users to know the underlying database schema. We evaluate our approach on over 450 natural language queries concerning three different databases, namely MAS, IMDB, and YELP. Our experiments show that the desired query is ranked within the top 5 candidates in close to 90% of the cases and that Sqlizer outperforms Nalir, a state-of-the-art tool that won a best paper award at VLDB'14. CCS Concepts: • Human-centered computing → Natural language interfaces; • Software and its engineering → Domain specific languages; • Information systems → Relational database query languages; Database utilities and tools; Extraction, transformation and loading;

This paper presents an example-driven synthesis technique for automating a large class of data preparation tasks that arise in data science. Given a set of input tables and an output table, our approach synthesizes a table transformation program that performs the desired task. Our approach is not restricted to a fixed set of DSL constructs and can synthesize programs from an arbitrary set of components, including higher-order combinators. At a high-level, our approach performs type-directed enumerative search over partial programs but incorporates two key innovations that allow it to scale: First, our technique can utilize any first-order specification of the components and uses SMT-based deduction to reject partial programs. Second, our algorithm uses partial evaluation to increase the power of deduction and drive enumerative search. We have evaluated our synthesis algorithm on dozens of data preparation tasks obtained from on-line forums, and we show that our approach can automatically solve a large class of problems encountered by R users.

Abstract. We describe a symbolic heap abstraction that unifies reasoning about arrays, pointers, and scalars, and we define a fluid update operation on this symbolic heap that relaxes the dichotomy between strong and weak updates. Our technique is fully automatic, does not suffer from the kind of state-space explosion problem partition-based approaches are prone to, and can naturally express properties that hold for non-contiguous array elements. We demonstrate the effectiveness of this technique by evaluating it on challenging array benchmarks and by automatically verifying buffer accesses and dereferences in five Unix Coreutils applications with no annotations or false alarms.

Unlike safety properties which require the absence of a "bad" program trace, k-safety properties stipulate the absence of a "bad" interaction between k traces. Examples of k-safety properties include transitivity, associativity, anti-symmetry, and monotonicity. This paper presents a sound and relatively complete calculus, called Cartesian Hoare Logic (CHL), for verifying k-safety properties. Our program logic is designed with automation and scalability in mind, allowing us to formulate a verification algorithm that automates reasoning in CHL. We have implemented our verification algorithm in a fully automated tool called DESCARTES, which can be used to analyze any k-safety property of Java programs. We have used DESCARTES to analyze user-defined relational operators and demonstrate that DESCARTES is effective at verifying (or finding violations of) multiple k-safety properties.

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Component-based approaches to program synthesis assemble programs from a database of existing components, such as methods provided by an API. In this paper, we present a novel type-directed algorithm for component-based synthesis. The key novelty of our approach is the use of a compact Petri-net representation to model relationships between methods in an API. Given a target method signature S, our approach performs reachability analysis on the underlying Petri-net model to identify sequences of method calls that could be used to synthesize an implementation of S. The programs synthesized by our algorithm are guaranteed to type check and pass all test cases provided by the user. We have implemented this approach in a tool called SYPET, and used it to successfully synthesize real-world programming tasks extracted from on-line forums and existing code repositories. We also compare SYPET with two state-of-the-art synthesis tools, namely INSYNTH and CODEHINT, and demonstrate that SYPET can synthesize more programs in less time. Finally, we compare our approach with an alternative solution based on hypergraphs and demonstrate its advantages.