Multi-Dispatch in the Java Virtual Machine: Design and Implementation
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Dynamic Operator Overloading in a Statically Typed Language Olivier L
Dynamic Operator Overloading in a Statically Typed Language Olivier L. Clerc and Felix O. Friedrich Computer Systems Institute, ETH Z¨urich, Switzerland [email protected], [email protected] October 31, 2011 Abstract Dynamic operator overloading provides a means to declare operators that are dispatched according to the runtime types of the operands. It allows to formulate abstract algorithms operating on user-defined data types using an algebraic notation, as it is typically found in mathematical languages. We present the design and implementation of a dynamic operator over- loading mechanism in a statically-typed object-oriented programming lan- guage. Our approach allows operator declarations to be loaded dynam- ically into a running system, at any time. We provide semantical rules that not only ensure compile-time type safety, but also facilitate the im- plementation. The spatial requirements of our approach scale well with a large number of types, because we use an adaptive runtime system that only stores dispatch information for type combinations that were encoun- tered previously at runtime. On average, dispatching can be performed in constant time. 1 Introduction Almost all programming languages have a built-in set of operators, such as +, -, * or /, that perform primitive arithmetic operations on basic data types. Operator overloading is a feature that allows the programmer to redefine the semantics of such operators in the context of custom data types. For that purpose, a set of operator implementations distinguished by their signatures has to be declared. Accordingly, each operator call on one or more custom-typed arguments will be dispatched to one of the implementations whose signature matches the operator's name and actual operand types. -
Strict Protection for Virtual Function Calls in COTS C++ Binaries
vfGuard: Strict Protection for Virtual Function Calls in COTS C++ Binaries Aravind Prakash Xunchao Hu Heng Yin Department of EECS Department of EECS Department of EECS Syracuse University Syracuse University Syracuse University [email protected] [email protected] [email protected] Abstract—Control-Flow Integrity (CFI) is an important se- these binary-only solutions are unfortunately coarse-grained curity property that needs to be enforced to prevent control- and permissive. flow hijacking attacks. Recent attacks have demonstrated that existing CFI protections for COTS binaries are too permissive, While coarse-grained CFI solutions have significantly re- and vulnerable to sophisticated code reusing attacks. Accounting duced the attack surface, recent efforts by Goktas¸¨ et al. [9] for control flow restrictions imposed at higher levels of semantics and Carlini [10] have demonstrated that coarse-grained CFI is key to increasing CFI precision. In this paper, we aim to provide solutions are too permissive, and can be bypassed by reusing more stringent protection for virtual function calls in COTS large gadgets whose starting addresses are allowed by these C++ binaries by recovering C++ level semantics. To achieve this solutions. The primary reason for such permissiveness is the goal, we recover C++ semantics, including VTables and virtual lack of higher level program semantics that introduce certain callsites. With the extracted C++ semantics, we construct a sound mandates on the control flow. For example, given a class CFI policy and further improve the policy precision by devising two filters, namely “Nested Call Filter” and “Calling Convention inheritance, target of a virtual function dispatch in C++ must Filter”. -
Behavioral Subtyping, Specification Inheritance, and Modular Reasoning Gary T
Computer Science Technical Reports Computer Science 9-3-2006 Behavioral Subtyping, Specification Inheritance, and Modular Reasoning Gary T. Leavens Iowa State University David A. Naumann Iowa State University Follow this and additional works at: http://lib.dr.iastate.edu/cs_techreports Part of the Software Engineering Commons Recommended Citation Leavens, Gary T. and Naumann, David A., "Behavioral Subtyping, Specification Inheritance, and Modular Reasoning" (2006). Computer Science Technical Reports. 269. http://lib.dr.iastate.edu/cs_techreports/269 This Article is brought to you for free and open access by the Computer Science at Iowa State University Digital Repository. It has been accepted for inclusion in Computer Science Technical Reports by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Behavioral Subtyping, Specification Inheritance, and Modular Reasoning Abstract Behavioral subtyping is an established idea that enables modular reasoning about behavioral properties of object-oriented programs. It requires that syntactic subtypes are behavioral refinements. It validates reasoning about a dynamically-dispatched method call, say E.m(), using the specification associated with the static type of the receiver expression E. For languages with references and mutable objects the idea of behavioral subtyping has not been rigorously formalized as such, the standard informal notion has inadequacies, and exact definitions are not obvious. This paper formalizes behavioral subtyping and supertype abstraction for a Java-like sequential language with classes, interfaces, exceptions, mutable heap objects, references, and recursive types. Behavioral subtyping is proved sound and semantically complete for reasoning with supertype abstraction. Specification inheritance, as used in the specification language JML, is formalized and proved to entail behavioral subtyping. -
Advances in Programming Languages Lecture 18: Concurrency and More in Rust
Advances in Programming Languages Lecture 18: Concurrency and More in Rust Ian Stark School of Informatics The University of Edinburgh Friday 24 November 2016 Semester 1 Week 10 https://blog.inf.ed.ac.uk/apl16 Topic: Programming for Memory Safety The final block of lectures cover features used in the Rust programming language. Introduction: Zero-Cost Abstractions (and their cost) Control of Memory: Ownership Concurrency and more This section of the course is entirely new — Rust itself is not that old — and I apologise for any consequent lack of polish. Ian Stark Advances in Programming Languages / Lecture 18: Concurrency and More in Rust 2016-11-24 The Rust Programming Language The Rust language is intended as a tool for safe systems programming. Three key objectives contribute to this. Zero-cost abstractions Basic References Memory safety https://www.rust-lang.org https://blog.rust-lang.org Safe concurrency The “systems programming” motivation resonates with that for imperative C/C++. The “safe” part draws extensively on techniques developed for functional Haskell and OCaml. Sometimes these align more closely than you might expect, often by overlap between two aims: Precise control for the programmer; Precise information for the compiler. Ian Stark Advances in Programming Languages / Lecture 18: Concurrency and More in Rust 2016-11-24 Previous Homework Watch This Peter O’Hearn: Reasoning with Big Code https://is.gd/reasoning_big_code Talk at the Alan Turing Institute about how Facebook is using automatic verification at scale to check code and give feedback to programmers. Ian Stark Advances in Programming Languages / Lecture 18: Concurrency and More in Rust 2016-11-24 Guest Speaker ! Probabilistic Programming: What is it and how do we make it better? Maria Gorinova University of Edinburgh 3.10pm Tuesday 29 November 2016 Ian Stark Advances in Programming Languages / Lecture 18: Concurrency and More in Rust 2016-11-24 Optional: Review and Exam Preparation ! The final lecture will be an exam review, principally for single-semester visiting students. -
Developing Rust on Bare-Metal
RustyGecko - Developing Rust on Bare-Metal An experimental embedded software platform Håvard Wormdal Høiby Sondre Lefsaker Master of Science in Computer Science Submission date: June 2015 Supervisor: Magnus Lie Hetland, IDI Co-supervisor: Antonio Garcia Guirado, IDI Marius Grannæs, Silicon Labs Norwegian University of Science and Technology Department of Computer and Information Science Preface This report is submitted to the Norwegian University of Science and Technology in fulfillment of the requirements for master thesis. This work has been performed at the Department of Computer and Information Science, NTNU, with Prof. Magnus Lie Hetland as the supervisor, Antonio Garcia Guirado (ARM), and Marius Grannæs (Silicon Labs) as co-supervisors. The initial problem description was our own proposal and further developed in co-operation with our supervisors. Acknowledgements Thanks to Magnus Lie Hetland, Antonio Garcia Guirado, and Marius Grannæs for directions and guidance on technical issues and this report. Thanks to Silicon Labs for providing us with development platforms for us to develop and test our implementation on. Thanks to Antonio Garcia Guirado for the implementation of the CircleGame application for us to port to Rust and use in our benchmarks. Thanks to Itera w/Tommy Ryen for office space. A special thanks to Leslie Ho and Siri Aagedal for all the support and for proofreading the thesis. Sondre Lefsaker and H˚avard Wormdal Høiby 2015-06-14 i Project Description The Rust programming language is a new system language developed by Mozilla. With the language being statically compiled and built on the LLVM compiler infras- tructure, and because of features like low-level control and zero-cost abstractions, the language is a candidate for use in bare-metal systems. -
Xtend User Guide
Xtend User Guide September 10, 2013 Contents I. Getting Started 5 1. Introduction 6 2. Hello World 7 3. The Movies Example 9 3.1. The Data . .9 3.2. Parsing The Data . 10 3.3. Answering Some Questions . 11 3.3.1. Question 1 : What Is The Number Of Action Movies? . 11 3.3.2. Question 2 : What Is The Year The Best Movie From The 80's Was Released? . 12 3.3.3. Question 3 : What Is The The Sum Of All Votes Of The Top Two Movies?................................. 13 II. Reference Documentation 14 4. Java Interoperability 15 4.1. Type Inference . 15 4.2. Conversion Rules . 15 4.3. Interoperability with Java . 16 5. Classes and Members 17 5.1. Package Declaration . 17 5.2. Imports . 17 5.3. Class Declaration . 18 5.4. Constructors . 19 5.5. Fields . 19 5.6. Methods . 20 5.6.1. Abstract Methods . 20 5.6.2. Overriding Methods . 21 5.6.3. Declared Exceptions . 21 5.6.4. Inferred Return Types . 21 5.6.5. Generic Methods . 22 2 5.6.6. Dispatch Methods . 22 5.7. Annotations . 26 5.8. Extension Methods . 26 5.8.1. Extensions from the Library . 27 5.8.2. Local Extension Methods . 28 5.8.3. Extension Imports . 28 5.8.4. Extension Provider . 29 5.9. Interface Declaration . 29 5.10. Annotation Type Declaration . 30 5.11. Enum Type Declaration . 30 6. Expressions 31 6.1. Literals . 31 6.1.1. String Literals . 31 6.1.2. Character Literals . 32 6.1.3. Number Literals . -
The Rust Programming Language
The Rust Programming Language The Rust Team 2016-10-01 2 Contents 1 Introduction 11 Contributing ...................................... 11 2 Getting Started 13 Installing Rust ..................................... 13 Hello, world! ...................................... 16 Hello, Cargo! ...................................... 19 Closing Thoughts .................................... 23 3 Tutorial: Guessing Game 25 Set up .......................................... 25 Processing a Guess ................................... 26 Generating a secret number .............................. 30 Comparing guesses ................................... 33 Looping ......................................... 37 Complete! ........................................ 41 4 Syntax and Semantics 43 Variable Bindings ....................................... 43 Patterns ......................................... 43 Type annotations .................................... 44 Mutability ........................................ 44 Initializing bindings .................................. 45 Scope and shadowing .................................. 46 Functions ........................................... 48 Primitive Types ........................................ 53 Booleans ......................................... 53 4 CONTENTS char ........................................... 53 Numeric types ..................................... 54 Arrays .......................................... 55 Slices ........................................... 56 str ........................................... -
Comparative Studies of 10 Programming Languages Within 10 Diverse Criteria Revision 1.0
Comparative Studies of 10 Programming Languages within 10 Diverse Criteria Revision 1.0 Rana Naim∗ Mohammad Fahim Nizam† Concordia University Montreal, Concordia University Montreal, Quebec, Canada Quebec, Canada [email protected] [email protected] Sheetal Hanamasagar‡ Jalal Noureddine§ Concordia University Montreal, Concordia University Montreal, Quebec, Canada Quebec, Canada [email protected] [email protected] Marinela Miladinova¶ Concordia University Montreal, Quebec, Canada [email protected] Abstract This is a survey on the programming languages: C++, JavaScript, AspectJ, C#, Haskell, Java, PHP, Scala, Scheme, and BPEL. Our survey work involves a comparative study of these ten programming languages with respect to the following criteria: secure programming practices, web application development, web service composition, OOP-based abstractions, reflection, aspect orientation, functional programming, declarative programming, batch scripting, and UI prototyping. We study these languages in the context of the above mentioned criteria and the level of support they provide for each one of them. Keywords: programming languages, programming paradigms, language features, language design and implementation 1 Introduction Choosing the best language that would satisfy all requirements for the given problem domain can be a difficult task. Some languages are better suited for specific applications than others. In order to select the proper one for the specific problem domain, one has to know what features it provides to support the requirements. Different languages support different paradigms, provide different abstractions, and have different levels of expressive power. Some are better suited to express algorithms and others are targeting the non-technical users. The question is then what is the best tool for a particular problem. -
COMP322 - Introduction to C++
COMP322 - Introduction to C++ Lecture 09 - Inheritance continued Robert D. Vincent School of Computer Science 10 March 2010 Recall from last time I Inheritance describes the creation of derived classes from base classes. I Derived classes inherit all data and functions from their base classes, while certain functions such as constructors are handled specially. I Polymorphism is a product of the combination of virtual functions and C++ assignment compatibility rules. I We can create abstract types which contain “pure” functions that may have no implementation. We can’t actually create objects from these types, but we can create references or pointers to abstract types. Static dispatch If a member function is not virtual, the choice of function to call is made at compile time: class A{ int f(); }; class B: public A{ int f(); }; int main() { B b; A *pa = &b; pa->f(); // Calls A::f() because pa is of type 'A *' } This is called either “static dispatch” or “static binding”, and it is the default behavior in C++. Dynamic dispatch If a member function is virtual, the choice of function to call is made at run time: class A{ virtual int f(); }; class B: public A{ int f(); }; int main() { B b; A *pa = &b; pa->f(); // Calls B::f() because pa points to a 'B *' } Called either “dynamic dispatch” or “run-time binding”, this is both more useful and less efficient than static dispatch. Dynamic dispatch internals I Dynamic dispatch is implemented by adding a layer of indirection to a function call. I Any object with dynamic dispatch contains an automatically-generated pointer to a vtable. -
Virtual Functions
Virtual Functions OK, today’s topic in Object Oriented C++ is function dispatch. First, let’s review overloading. What is function overloading? Two methods or functions with the same signature. Why do you overload a function? For polymorphism. Now, mechanically, how do you overload something? Not only the method name, but the number and type of arguments and the return type must all match. Why? The name and arguments so that you know it’s an overload; the return type so that the compiler always knows the data types at run time… OK, so let’s create an example of overloading. Let’s say I have an Animal class with a “warm up” method. It might look like: Class Animal { Public: bool Warm-up() const {return false;} void Behave() { if (cold()) warm-up(); } }; Notice that is returns false, because there is no way for a generic Animal to warm up. But if we get more specific… Class Mammal : public Animal { Public: Bool Warm-up() const {shiver(); return true;} }; Notice that this is an example of function overloading, because the name, arguments and return type all match. Now, what happens if I write the following code? Mammal m; m.Behave(); In particular, which version of Behave() gets called? Notice that m is a mammal, but Behave() is a method of Animal, so inside Animal() the declared type of the object is Animal, not Mammal. If I did this example in Java, the answer is that the mammal would shiver and return true. But as written, in C++ the animal does nothing and Warm_up returns false. -
Multimethods
11-A1568 01/23/2001 12:39 PM Page 263 11 Multimethods This chapter defines, discusses, and implements multimethods in the context of Cϩϩ . The Cϩϩ virtual function mechanism allows dispatching a call depending on the dynamic type of one object. The multimethods feature allows dispatching a function call depending on the types of multiple objects. A universally good implementation requires language support, which is the route that languages such as CLOS, ML, Haskell, and Dylan have taken. Cϩϩ lacks such support, so its emulation is left to library writers. This chapter discusses some typical solutions and some generic implementations of each. The solutions feature various trade-offs in terms of speed, flexibility, and dependency management. To describe the technique of dispatching a function call depending on mul- tiple objects, this book uses the terms multimethod (borrowed from CLOS) and multiple dis- patch. A particularization of multiple dispatch for two objects is known as double dispatch. Implementing multimethods is a problem as fascinating as dreaded, one that has stolen lots of hours of good, healthy sleep from designers and programmers.1 The topics of this chapter include • Defining multimethods • Identifying situations in which the need for multiobject polymorphism appears • Discussing and implementing three double dispatchers that foster different trade-offs • Enhancing double-dispatch engines After reading this chapter, you will have a firm grasp of the typical situations for which multimethods are the way to go. In addition, you will be able to use and extend several ro- bust generic components implementing multimethods, provided by Loki. This chapter limits discussion to multimethods for two objects (double dispatch). -
Multiple Dispatch and Roles in OO Languages: Ficklemr
Multiple Dispatch and Roles in OO Languages: FickleMR Submitted By: Asim Anand Sinha [email protected] Supervised By: Sophia Drossopoulou [email protected] Department of Computing IMPERIAL COLLEGE LONDON MSc Project Report 2005 September 13, 2005 Abstract Object-Oriented Programming methodology has been widely accepted because it allows easy modelling of real world concepts. The aim of research in object-oriented languages has been to extend its features to bring it as close as possible to the real world. In this project, we aim to add the concepts of multiple dispatch and first-class relationships to a statically typed, class based langauges to make them more expressive. We use Fickle||as our base language and extend its features in FickleMR . Fickle||is a statically typed language with support for object reclassification, it allows objects to change their class dynamically. We study the impact of introducing multiple dispatch and roles in FickleMR . Novel idea of relationship reclassification and more flexible multiple dispatch algorithm are most interesting. We take a formal approach and give a static type system and operational semantics for language constructs. Acknowledgements I would like to take this opportunity to express my heartful gratitude to DR. SOPHIA DROSSOPOULOU for her guidance and motivation throughout this project. I would also like to thank ALEX BUCKLEY for his time, patience and brilliant guidance in the abscence of my supervisor. 1 Contents 1 Introduction 5 2 Background 8 2.1 Theory of Objects . 8 2.2 Single and Double Dispatch . 10 2.3 Multiple Dispatch . 12 2.3.1 Challenges in Implementation .