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96
FlowSensitive Type Qualifiers
, 2002
"... We present a system for extending standard type systems with flowsensitive type qualifiers. Users annotate their programs with type qualifiers, and inference checks that the annotations are correct. In our system only the type qualifiers are modeled flowsensitively  the underlying standard types ..."
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Cited by 407 (29 self)
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We present a system for extending standard type systems with flowsensitive type qualifiers. Users annotate their programs with type qualifiers, and inference checks that the annotations are correct. In our system only the type qualifiers are modeled flowsensitively  the underlying standard types are unchanged, which allows us to obtain an efficient constraintbased inference algorithm that integrates flowinsensitive alias analysis, effect inference, and ideas from linear type systems to support strong updates. We demonstrate the usefulness of flowsensitive type qualifiers by finding a number of new locking bugs in the Linux kernel.
Detecting Format String Vulnerabilities with Type Qualifiers
, 2001
"... We present a new system for automatically detecting format string security vulnerabilities in C programs using a constraintbased typeinference engine. We describe new techniques for presenting the results of such an analysis to the user in a form that makes bugs easier to find and to fix. The syst ..."
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Cited by 228 (13 self)
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We present a new system for automatically detecting format string security vulnerabilities in C programs using a constraintbased typeinference engine. We describe new techniques for presenting the results of such an analysis to the user in a form that makes bugs easier to find and to fix. The system has been implemented and tested on several realworld software packages. Our tests show that the system is very effective, detecting several bugs previously unknown to the authors and exhibiting a low rate of false positives in almost all cases. Many of our techniques are applicable to additional classes of security vulnerabilities, as well as other type and constraintbased systems.
A Practical Soft Type System for Scheme
 In Proceedings of the 1994 ACM Conference on LISP and Functional Programming
, 1993
"... Soft type systems provide the benefits of static type checking for dynamically typed languages without rejecting untypable programs. A soft type checker infers types for variables and expressions and inserts explicit runtime checks to transform untypable programs to typable form. We describe a prac ..."
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Cited by 117 (4 self)
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Soft type systems provide the benefits of static type checking for dynamically typed languages without rejecting untypable programs. A soft type checker infers types for variables and expressions and inserts explicit runtime checks to transform untypable programs to typable form. We describe a practical soft type system for R4RS Scheme. Our type checker uses a representation for types that is expressive, easy to interpret, and supports efficient type inference. Soft Scheme supports all of R4RS Scheme, including procedures of fixed and variable arity, assignment, continuations, and toplevel definitions. Our implementation is available by anonymous FTP. The first author was supported in part by the United States Department of Defense under a National Defense Science and Engineering Graduate Fellowship. y The second author was supported by NSF grant CCR9122518 and the Texas Advanced Technology Program under grant 003604014. 1 Introduction Dynamically typed languages like Scheme...
The Marriage of Effects and Monads
, 1998
"... this paper is to marry effects to monads, writing T for a computation that yields a value in and may have effects delimited by oe. Now we have that ( is ..."
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Cited by 117 (7 self)
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this paper is to marry effects to monads, writing T for a computation that yields a value in and may have effects delimited by oe. Now we have that ( is
Practical Dynamic Software Updating
, 2008
"... This dissertation makes the case that programs can be updated while they run, with modest programmer effort, while providing certain update safety guarantees, and without imposing a significant performance overhead. Few systems are designed with onthefly updating in mind. Those systems that permit ..."
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Cited by 103 (31 self)
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This dissertation makes the case that programs can be updated while they run, with modest programmer effort, while providing certain update safety guarantees, and without imposing a significant performance overhead. Few systems are designed with onthefly updating in mind. Those systems that permit it support only a very limited class of updates, and generally provide no guarantees that following the update, the system will behave as intended. We tackle the onthefly updating problem using a compilerbased approach called dynamic software updating (DSU), in which a program is patched with new code and data while it runs. The challenge is in making DSU practical: it should support changes to programs as they occur in practice, yet be safe, easy to use, and not impose a large overhead. This dissertation makes both theoretical contributions—formalisms for reasoning about, and ensuring update safety—and practical contributions—Ginseng, a DSU implementation for C. Ginseng supports a broad range of changes to C programs, and performs a suite of safety analyses to ensure certain update safety
What Are Principal Typings and What Are They Good For?
, 1995
"... We demonstrate the pragmatic value of the principal typing property, a property more general than ML's principal type property, by studying a type system with principal typings. The type system is based on rank 2 intersection types and is closely related to ML. Its principal typing property ..."
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Cited by 102 (0 self)
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We demonstrate the pragmatic value of the principal typing property, a property more general than ML's principal type property, by studying a type system with principal typings. The type system is based on rank 2 intersection types and is closely related to ML. Its principal typing property provides elegant support for separate compilation, including "smartest recompilation" and incremental type inference, and for accurate type error messages. Moreover, it motivates a novel rule for typing recursive definitions that can type many examples of polymorphic recursion.
Introduction to set constraintbased program analysis
 Science of Computer Programming
, 1999
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Once Upon a Type
 In Functional Programming Languages and Computer Architecture
, 1995
"... A number of useful optimisations are enabled if we can determine when a value is accessed at most once. We extend the HindleyMilner type system with uses, yielding a typeinference based program analysis which determines when values are accessed at most once. Our analysis can handle higherorder fun ..."
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Cited by 89 (2 self)
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A number of useful optimisations are enabled if we can determine when a value is accessed at most once. We extend the HindleyMilner type system with uses, yielding a typeinference based program analysis which determines when values are accessed at most once. Our analysis can handle higherorder functions and data structures, and admits principal types for terms. Unlike previous analyses, we prove our analysis sound with respect to callbyneed reduction. Callbyname reduction does not provide an accurate model of how often a value is used during lazy evaluation, since it duplicates work which would actually be shared in a real implementation. Our type system can easily be modified to analyse usage in a callbyvalue language. 1 Introduction This paper describes a method for determining when a value is used at most once. Our method is based on a simple modification of the HindleyMilner type system. Each type is labelled to indicate whether the corresponding value is used at most onc...
Subtyping Constrained Types
, 1996
"... A constrained type is a type that comes with a set of subtyping constraints on variables occurring in the type. Constrained type inference systems are a natural generalization of Hindley/Milner type inference to languages with subtyping. This paper develops several subtyping relations on polymorphic ..."
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Cited by 63 (2 self)
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A constrained type is a type that comes with a set of subtyping constraints on variables occurring in the type. Constrained type inference systems are a natural generalization of Hindley/Milner type inference to languages with subtyping. This paper develops several subtyping relations on polymorphic constrained types of a general form that allows recursive constraints and multiple bounds on type variables. We establish a full type abstraction property that equates a novel operational notion of subtyping with a semantic notion based on regular trees. The decidability of this notion of subtyping is open; we present a decidable approximation. Subtyping constrained types has applications to signature matching and to constrained type simplification. The relation will thus be a critical component of any programming language incorporating a constrained typing system. 1 Introduction A constrained type is a type that is additionally constrained by a set of subtyping constraints on the free ty...
A modular, polyvariant, and typebased closure analysis
 In ICFP ’97 [ICFP97
"... We observe that the principal typing property of a type system is the enabling technology for modularity and separate compilation [10]. We use this technology to formulate a modular and polyvariant closure analysis, based on the rank 2 intersection types annotated with controlflow information. Modu ..."
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Cited by 57 (1 self)
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We observe that the principal typing property of a type system is the enabling technology for modularity and separate compilation [10]. We use this technology to formulate a modular and polyvariant closure analysis, based on the rank 2 intersection types annotated with controlflow information. Modularity manifests itself in a syntaxdirected, annotatedtype inference algorithm that can analyse program fragments containing free variables: a principal typing property is used to formalise it. Polyvariance manifests itself in the separation of different behaviours of the same function at its different uses: this is formalised via the rank 2 intersection types. As the rank 2 intersection type discipline types at least all (core) ML programs, our analysis can be used in the separate compilation of such programs. 1