Memory Safety, Continued with Material from Mike Hicks, Dave Levin and Michelle Mazurek
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Memory Safety Without Garbage Collection for Embedded Applications
Memory Safety Without Garbage Collection for Embedded Applications DINAKAR DHURJATI, SUMANT KOWSHIK, VIKRAM ADVE, and CHRIS LATTNER University of Illinois at Urbana-Champaign Traditional approaches to enforcing memory safety of programs rely heavily on run-time checks of memory accesses and on garbage collection, both of which are unattractive for embedded ap- plications. The goal of our work is to develop advanced compiler techniques for enforcing memory safety with minimal run-time overheads. In this paper, we describe a set of compiler techniques that, together with minor semantic restrictions on C programs and no new syntax, ensure memory safety and provide most of the error-detection capabilities of type-safe languages, without using garbage collection, and with no run-time software checks, (on systems with standard hardware support for memory management). The language permits arbitrary pointer-based data structures, explicit deallocation of dynamically allocated memory, and restricted array operations. One of the key results of this paper is a compiler technique that ensures that dereferencing dangling pointers to freed memory does not violate memory safety, without annotations, run-time checks, or garbage collection, and works for arbitrary type-safe C programs. Furthermore, we present a new inter- procedural analysis for static array bounds checking under certain assumptions. For a diverse set of embedded C programs, we show that we are able to ensure memory safety of pointer and dy- namic memory usage in all these programs with no run-time software checks (on systems with standard hardware memory protection), requiring only minor restructuring to conform to simple type restrictions. Static array bounds checking fails for roughly half the programs we study due to complex array references, and these are the only cases where explicit run-time software checks would be needed under our language and system assumptions. -
Javascript • Data Types • Operators • Control Statement • Popup Boxes • Functions • Arrays
LECTURE-2 Javascript • Data types • Operators • Control Statement • Popup Boxes • Functions • Arrays CS3101: Programming Languages: Javascript Ramana Isukapalli 1 JAVASCRIPT – OVERVIEW • This course is concerned with client side JS • Executes on client (browser) • Scripting – NOT compile/link. • Helps provide dynamic nature of HTML pages. • Included as part of HTML pages as • Regular code (viewable by user) • A file present in some location. • NOTE: Javascript is NOT the same as JAVA CS3101: Programming Languages: Javascript Ramana Isukapalli 2 A SIMPLE JAVASCRIPT PROGRAM <html> <head> <title> A simple Javascript program </title> </head> <body> <! --The code below in “script” is Javascript code. --> <script> document.write (“A Simple Javascript program”); </script> </body> </html> CS3101: Programming Languages: Javascript Ramana Isukapalli 3 JAVASCRIPT CODE • Javascript code in HTML • Javascript code can be placed in • <head> part of HTML file • Code is NOT executed unless called in <body> part of the file. • <body> part of HTML file – executed along with the rest of body part. • Outside HTML file, location is specified. • Executed when called in <body> CS3101: Programming Languages: Javascript Ramana Isukapalli 4 WAYS OF DEFINING JAVASCRIPT CODE. First: Second: <head> <head> <script type=“text/javascript”> … function foo(…) // defined here </head> <body> </script> <script> </head> function foo(…) // defined here { <body> .. } <script type=“text/javascript”> foo( ) // Called here foo(…) // called here </script> </script> </body> </body> -
Memory Leak Or Dangling Pointer
Modern C++ for Computer Vision and Image Processing Igor Bogoslavskyi Outline Using pointers Pointers are polymorphic Pointer “this” Using const with pointers Stack and Heap Memory leaks and dangling pointers Memory leak Dangling pointer RAII 2 Using pointers in real world Using pointers for classes Pointers can point to objects of custom classes: 1 std::vector<int> vector_int; 2 std::vector<int >* vec_ptr = &vector_int; 3 MyClass obj; 4 MyClass* obj_ptr = &obj; Call object functions from pointer with -> 1 MyClass obj; 2 obj.MyFunc(); 3 MyClass* obj_ptr = &obj; 4 obj_ptr->MyFunc(); obj->Func() (*obj).Func() ↔ 4 Pointers are polymorphic Pointers are just like references, but have additional useful properties: Can be reassigned Can point to ‘‘nothing’’ (nullptr) Can be stored in a vector or an array Use pointers for polymorphism 1 Derived derived; 2 Base* ptr = &derived; Example: for implementing strategy store a pointer to the strategy interface and initialize it with nullptr and check if it is set before calling its methods 5 1 #include <iostream > 2 #include <vector > 3 using std::cout; 4 struct AbstractShape { 5 virtual void Print() const = 0; 6 }; 7 struct Square : public AbstractShape { 8 void Print() const override { cout << "Square\n";} 9 }; 10 struct Triangle : public AbstractShape { 11 void Print() const override { cout << "Triangle\n";} 12 }; 13 int main() { 14 std::vector<AbstractShape*> shapes; 15 Square square; 16 Triangle triangle; 17 shapes.push_back(&square); 18 shapes.push_back(&triangle); 19 for (const auto* shape : shapes) { shape->Print(); } 20 return 0; 21 } 6 this pointer Every object of a class or a struct holds a pointer to itself This pointer is called this Allows the objects to: Return a reference to themselves: return *this; Create copies of themselves within a function Explicitly show that a member belongs to the current object: this->x(); 7 Using const with pointers Pointers can point to a const variable: 1 // Cannot change value , can reassign pointer. -
Typescript-Handbook.Pdf
This copy of the TypeScript handbook was created on Monday, September 27, 2021 against commit 519269 with TypeScript 4.4. Table of Contents The TypeScript Handbook Your first step to learn TypeScript The Basics Step one in learning TypeScript: The basic types. Everyday Types The language primitives. Understand how TypeScript uses JavaScript knowledge Narrowing to reduce the amount of type syntax in your projects. More on Functions Learn about how Functions work in TypeScript. How TypeScript describes the shapes of JavaScript Object Types objects. An overview of the ways in which you can create more Creating Types from Types types from existing types. Generics Types which take parameters Keyof Type Operator Using the keyof operator in type contexts. Typeof Type Operator Using the typeof operator in type contexts. Indexed Access Types Using Type['a'] syntax to access a subset of a type. Create types which act like if statements in the type Conditional Types system. Mapped Types Generating types by re-using an existing type. Generating mapping types which change properties via Template Literal Types template literal strings. Classes How classes work in TypeScript How JavaScript handles communicating across file Modules boundaries. The TypeScript Handbook About this Handbook Over 20 years after its introduction to the programming community, JavaScript is now one of the most widespread cross-platform languages ever created. Starting as a small scripting language for adding trivial interactivity to webpages, JavaScript has grown to be a language of choice for both frontend and backend applications of every size. While the size, scope, and complexity of programs written in JavaScript has grown exponentially, the ability of the JavaScript language to express the relationships between different units of code has not. -
Section “Common Predefined Macros” in the C Preprocessor
The C Preprocessor For gcc version 12.0.0 (pre-release) (GCC) Richard M. Stallman, Zachary Weinberg Copyright c 1987-2021 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation. A copy of the license is included in the section entitled \GNU Free Documentation License". This manual contains no Invariant Sections. The Front-Cover Texts are (a) (see below), and the Back-Cover Texts are (b) (see below). (a) The FSF's Front-Cover Text is: A GNU Manual (b) The FSF's Back-Cover Text is: You have freedom to copy and modify this GNU Manual, like GNU software. Copies published by the Free Software Foundation raise funds for GNU development. i Table of Contents 1 Overview :::::::::::::::::::::::::::::::::::::::: 1 1.1 Character sets:::::::::::::::::::::::::::::::::::::::::::::::::: 1 1.2 Initial processing ::::::::::::::::::::::::::::::::::::::::::::::: 2 1.3 Tokenization ::::::::::::::::::::::::::::::::::::::::::::::::::: 4 1.4 The preprocessing language :::::::::::::::::::::::::::::::::::: 6 2 Header Files::::::::::::::::::::::::::::::::::::: 7 2.1 Include Syntax ::::::::::::::::::::::::::::::::::::::::::::::::: 7 2.2 Include Operation :::::::::::::::::::::::::::::::::::::::::::::: 8 2.3 Search Path :::::::::::::::::::::::::::::::::::::::::::::::::::: 9 2.4 Once-Only Headers::::::::::::::::::::::::::::::::::::::::::::: 9 2.5 Alternatives to Wrapper #ifndef :::::::::::::::::::::::::::::: -
Getting Started with Nxopen
Getting Started with NX Open Update January 2019 © 2019 Siemens Product Lifecycle Management Software Inc. All rights reserved. Unrestricted Table of Contents Chapter 1: Introduction ....................................... 1 Chapter 8: Simple Solids and Sheets ............... 64 What Is NX Open .............................................................................................. 1 Creating Primitive Solids ........................................................................... 64 Purpose of this Guide ..................................................................................... 1 Sections ............................................................................................................. 65 Where To Go From Here ............................................................................... 1 Extruded Bodies ............................................................................................ 67 Other Documentation .................................................................................... 2 Revolved Bodies ............................................................................................ 68 Example Code .................................................................................................... 3 Chapter 9: Object Properties & Methods .......... 69 Chapter 2: Using the NX Journal Editor ............. 4 NXObject Properties .................................................................................... 69 System Requirement — The .NET Framework .................................. -
An Evolutionary Study of Linux Memory Management for Fun and Profit Jian Huang, Moinuddin K
An Evolutionary Study of Linux Memory Management for Fun and Profit Jian Huang, Moinuddin K. Qureshi, and Karsten Schwan, Georgia Institute of Technology https://www.usenix.org/conference/atc16/technical-sessions/presentation/huang This paper is included in the Proceedings of the 2016 USENIX Annual Technical Conference (USENIX ATC ’16). June 22–24, 2016 • Denver, CO, USA 978-1-931971-30-0 Open access to the Proceedings of the 2016 USENIX Annual Technical Conference (USENIX ATC ’16) is sponsored by USENIX. An Evolutionary Study of inu emory anagement for Fun and rofit Jian Huang, Moinuddin K. ureshi, Karsten Schwan Georgia Institute of Technology Astract the patches committed over the last five years from 2009 to 2015. The study covers 4587 patches across Linux We present a comprehensive and uantitative study on versions from 2.6.32.1 to 4.0-rc4. We manually label the development of the Linux memory manager. The each patch after carefully checking the patch, its descrip- study examines 4587 committed patches over the last tions, and follow-up discussions posted by developers. five years (2009-2015) since Linux version 2.6.32. In- To further understand patch distribution over memory se- sights derived from this study concern the development mantics, we build a tool called MChecker to identify the process of the virtual memory system, including its patch changes to the key functions in mm. MChecker matches distribution and patterns, and techniues for memory op- the patches with the source code to track the hot func- timizations and semantics. Specifically, we find that tions that have been updated intensively. -
Boost.Typeof Arkadiy Vertleyb Peder Holt Copyright © 2004, 2005 Arkadiy Vertleyb, Peder Holt
Boost.Typeof Arkadiy Vertleyb Peder Holt Copyright © 2004, 2005 Arkadiy Vertleyb, Peder Holt Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at ht- tp://www.boost.org/LICENSE_1_0.txt ) Table of Contents Motivation ............................................................................................................................................................ 2 Tutorial ................................................................................................................................................................ 4 Reference ............................................................................................................................................................. 7 AUTO, AUTO_TPL ....................................................................................................................................... 7 COMPLIANT ............................................................................................................................................... 7 INCREMENT_REGISTRATION_GROUP ......................................................................................................... 7 INTEGRAL .................................................................................................................................................. 8 LIMIT_FUNCTION_ARITY ........................................................................................................................... 8 MESSAGES ................................................................................................................................................ -
ILE C/C++ Language Reference, SC09-7852
IBM IBM i Websphere Development Studio ILE C/C++ Language Reference 7.1 SC09-7852-02 IBM IBM i Websphere Development Studio ILE C/C++ Language Reference 7.1 SC09-7852-02 Note! Before using this information and the product it supports, be sure to read the general information under “Notices” on page 355. This edition applies to IBM i 7.1, (program 5770-WDS), ILE C/C++ compilers, and to all subsequent releases and modifications until otherwise indicated in new editions. This version does not run on all reduced instruction set computer (RISC) models nor does it run on CISC models. © Copyright IBM Corporation 1998, 2010. US Government Users Restricted Rights – Use, duplication or disclosure restricted by GSA ADP Schedule Contract with IBM Corp. Contents About ILE C/C++ Language Reference Digraph characters ........... 27 (SC09-7852-01) ........... ix Trigraph sequences ........... 28 Who should read this book ......... ix Comments............... 28 Highlighting Conventions .......... x How to Read the Syntax Diagrams ....... x Chapter 3. Data objects and Prerequisite and related information ...... xii declarations ............ 31 How to send your comments ........ xii Overview of data objects and declarations .... 31 Overview of data objects ......... 31 What's new for IBM i 7.1 ....... xv Incomplete types .......... 32 Compatible and composite types ..... 32 Chapter 1. Scope and linkage ..... 1 Overview of data declarations and definitions .. 33 Tentative definitions ......... 34 Scope ................. 1 Storage class specifiers........... 35 Block/local scope ............ 2 The auto storage class specifier ....... 35 Function scope ............ 2 Storage duration of automatic variables ... 35 Function prototype scope ......... 3 Linkage of automatic variables ...... 36 File/global scope ........... -
Decltype and Auto (Revision 4) Programming Language C++ Document No: N1705=04-0145
Decltype and auto (revision 4) Programming Language C++ Document no: N1705=04-0145 Jaakko Järvi Bjarne Stroustrup Gabriel Dos Reis Texas A&M University AT&T Research Texas A&M University College Station, TX and Texas A&M University College Station, TX [email protected] [email protected] [email protected] September 12, 2004 1 Background This document is a revision of the documents N1607=04-0047 [JS04], N1527=03-0110 [JS03], and N1478=03- 0061 [JSGS03], and builds also on [Str02]. We assume the reader is familiar with the motivation for and history behind decltype and auto, and do not include background discussion in this document; see N1607=04-0047 [JS04] for that. We merely summarize, with two examples, the key capabilities that the proposed features would bring to the language: 1. Declaring return types of functions that depend on the parameter types in a non-trivial way: template <class A, class B> auto operator+(const Matrix<A>& a, const Matrix<B>& b) −> Matrix<decltype(a(0, 0) + b(0, 0))>; 2. Deducing the type of a variable from the type of its initializer: template <class A, class B> void foo(const A& a, const B& b) { auto tmp = a ∗ b; ... 1.1 Changes from N1607 Changes to the previous revisions primarily reflect the EWG discussions and results of the straw votes that took place in the Kona and Sydney meetings. In addition, we suggest a change to the rules of decltype for certain built-in operators, and for expressions that refer to member variables. Following is the list of changes from proposal N1607. -
The Building Blocks: Data Types, Literals, and Variables
Quigley.book Page 31 Thursday, May 22, 2003 3:19 PM chapter 3 The Building Blocks: Data Types, Literals, and Variables 3.1 Data Types A program can do many things, including calculations, sorting names, preparing phone lists, displaying images, validating forms, ad infinitum. But in order to do anything, the program works with the data that is given to it. Data types specify what kind of data, such as numbers and characters, can be stored and manipulated within a program. Java- Script supports a number of fundamental data types. These types can be broken down into two categories, primitive data types and composite data types. 3.1.1 Primitive Data Types Primitive data types are the simplest building blocks of a program. They are types that can be assigned a single literal value such as the number 5.7, or a string of characters such as "hello". JavaScript supports three core or basic data types: • numeric • string • Boolean In addition to the three core data types, there are two other special types that consist of a single value: • null • undefined Numeric Literals. JavaScript supports both integers and floating-point numbers. Integers are whole numbers and do not contain a decimal point; e.g., 123 and –6. Inte- gers can be expressed in decimal (base 10), octal (base 8), and hexadecimal (base 16), and are either positive or negative values. See Example 3.1. 31 Quigley.book Page 32 Thursday, May 22, 2003 3:19 PM 32 Chapter 3 • The Building Blocks: Data Types, Literals, and Variables Floating-point numbers are fractional numbers such as 123.56 or –2.5. -
C++0X Type Inference
Master seminar C++0x Type Inference Stefan Schulze Frielinghaus November 18, 2009 Abstract This article presents the new type inference features of the up- coming C++ standard. The main focus is on the keywords auto and decltype which introduce basic type inference. Their power but also their limitations are discussed in relation to full type inference of most functional programming languages. 1 Introduction Standard C++ requires explicitly a type for each variable (s. [6, § 7.1.5 clause 2]). There is no exception and especially when types get verbose it is error prone to write them. The upcoming C++ standard, from now on referenced as C++0x, includes a new functionality called type inference to circumvent this problem. Consider the following example: int a = 2; int b = 40; auto c = a + b; In this case the compiler may figure out the type of variable ‘c’ because the type of the rvalue of expression ‘a + b’ is known at compile time. In the end this means that the compiler may look up all variables and function calls of interest to figure out which type an object should have. This is done via type inference and the auto keyword. Often types get verbose when templates are used. These cases demonstrate how useful the auto keyword is. For example, in C++98 and 03 developers often use typedef to circumvent the problem of verbose types: 1 typedef std::vector<std::string> svec; ... svec v = foo(); In C++0x a typedef may be left out in favor of auto: auto v = foo(); In some cases it may reduce the overhead if someone is not familiar with a code and would therefore need to lookup all typedefs (s.