Bounded pointer

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In computer science, a bounded pointer is a pointer that is augmented with additional information that enable the storage bounds within which it may point to be deduced. [1] This additional information sometimes takes the form of two pointers holding the upper and lower addresses of the storage occupied by the object to which the bounded pointer points.

Computer science study of the theoretical foundations of information and computation

Computer science is the study of processes that interact with data and that can be represented as data in the form of programs. It enables the use of algorithms to manipulate, store, and communicate digital information. A computer scientist studies the theory of computation and the practice of designing software systems.

Pointer (computer programming) programming language data type

In computer science, a pointer is a programming language object that stores the memory address of another value located in computer memory. A pointer references a location in memory, and obtaining the value stored at that location is known as dereferencing the pointer. As an analogy, a page number in a book's index could be considered a pointer to the corresponding page; dereferencing such a pointer would be done by flipping to the page with the given page number and reading the text found on that page. The actual format and content of a pointer variable is dependent on the underlying computer architecture.

In computing, a memory address is a reference to a specific memory location used at various levels by software and hardware. Memory addresses are fixed-length sequences of digits conventionally displayed and manipulated as unsigned integers. Such numerical semantic bases itself upon features of CPU, as well upon use of the memory like an array endorsed by various programming languages.

Use of bound information makes it possible for a compiler to generate code that performs bounds checking, i.e. that tests if a pointer's value lies within the bounds prior to dereferencing the pointer or modifying the value of the pointer. If the bounds are violated some kind of exception may be raised. This is especially useful for data constructs such as arrays in C.

A compiler is a computer program that transforms computer code written in one programming language into another programming language. Compilers are a type of translator that support digital devices, primarily computers. The name compiler is primarily used for programs that translate source code from a high-level programming language to a lower level language to create an executable program.

In computer programming, bounds checking is any method of detecting whether a variable is within some bounds before it is used. It is usually used to ensure that a number fits into a given type, or that a variable being used as an array index is within the bounds of the array. A failed bounds check usually results in the generation of some sort of exception signal.

In computer science, an array data structure, or simply an array, is a data structure consisting of a collection of elements, each identified by at least one array index or key. An array is stored such that the position of each element can be computed from its index tuple by a mathematical formula. The simplest type of data structure is a linear array, also called one-dimensional array.

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In computer science, bounds-checking elimination is a compiler optimization useful in programming languages or runtimes that enforce bounds checking, the practice of checking every index into an array to verify that the index is within the defined valid range of indexes. Its goal is to detect which of these indexing operations do not need to be validated at runtime, and eliminating those checks.

In computer science, a smart pointer is an abstract data type that simulates a pointer while providing added features, such as automatic memory management or bounds checking. Such features are intended to reduce bugs caused by the misuse of pointers, while retaining efficiency. Smart pointers typically keep track of the memory they point to, and may also be used to manage other resources, such as network connections and file handles. Smart pointers were first popularized in the programming language C++ during the first half of the 1990s as rebuttal to criticisms of C++'s lack of automatic garbage collection.

In computer science, a tagged pointer is a pointer with additional data associated with it, such as an indirection bit or reference count. This additional data is often "folded" into the pointer, meaning stored inline in the data representing the address, taking advantage of certain properties of memory addressing. The name comes from "tagged union", and the additional data is called a "tag" or "tags", though strictly speaking "tag" refers to data specifying a type, not other data; however, the usage "tagged pointer" is standard.

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In information security and programming, a buffer overflow, or buffer overrun, is an anomaly where a program, while writing data to a buffer, overruns the buffer's boundary and overwrites adjacent memory locations.

C (programming language) general-purpose programming language

C is a general-purpose, imperative computer programming language, supporting structured programming, lexical variable scope and recursion, while a static type system prevents many unintended operations. By design, C provides constructs that map efficiently to typical machine instructions, and it has therefore found lasting use in applications that were previously coded in assembly language. Such applications include operating systems, as well as various application software for computers ranging from supercomputers to embedded systems.

The Cyclone programming language is intended to be a safe dialect of the C language. Cyclone is designed to avoid buffer overflows and other vulnerabilities that are possible in C programs, without losing the power and convenience of C as a tool for system programming.

This is a comparison of Java and C++, two prominent object-oriented programming languages.

In computer science, a reference is a value that enables a program to indirectly access a particular datum, such as a variable's value or a record, in the computer's memory or in some other storage device. The reference is said to refer to the datum, and accessing the datum is called dereferencing the reference.

The syntax of the C programming language, the rules governing writing of software in the language, is designed to allow for programs that are extremely terse, have a close relationship with the resulting object code, and yet provide relatively high-level data abstraction. C was the first widely successful high-level language for portable operating-system development.

In computer programming, undefined behavior (UB) is the result of executing computer code whose behavior is not prescribed by the language specification to which the code adheres, for the current state of the program. This happens when the translator of the source code makes certain assumptions, but these assumptions are not satisfied during execution.

Buffer overflow protection is any of various techniques used during software development to enhance the security of executable programs by detecting buffer overflows on stack-allocated variables, and preventing them from causing program misbehavior or from becoming serious security vulnerabilities. A stack buffer overflow occurs when a program writes to a memory address on the program's call stack outside of the intended data structure, which is usually a fixed-length buffer. Stack buffer overflow bugs are caused when a program writes more data to a buffer located on the stack than what is actually allocated for that buffer. This almost always results in corruption of adjacent data on the stack, which could lead to program crashes, incorrect operation, or security issues.

In computer science, cycle detection or cycle finding is the algorithmic problem of finding a cycle in a sequence of iterated function values.

In computing, aliasing describes a situation in which a data location in memory can be accessed through different symbolic names in the program. Thus, modifying the data through one name implicitly modifies the values associated with all aliased names, which may not be expected by the programmer. As a result, aliasing makes it particularly difficult to understand, analyze and optimize programs. Aliasing analysers intend to make and compute useful information for understanding aliasing in programs.

In the C++ programming language, a reference is a simple reference datatype that is less powerful but safer than the pointer type inherited from C. The name C++ reference may cause confusion, as in computer science a reference is a general concept datatype, with pointers and C++ references being specific reference datatype implementations. The definition of a reference in C++ is such that it does not need to exist. It can be implemented as a new name for an existing object.

Dangling pointer pointer that does not point to a valid object

Dangling pointers and wild pointers in computer programming are pointers that do not point to a valid object of the appropriate type. These are special cases of memory safety violations. More generally, dangling references and wild references are references that do not resolve to a valid destination, and include such phenomena as link rot on the internet.

Boundedness or bounded may refer to:

This is an overview of Fortran 95 language features. Included are the additional features of TR-15581:Enhanced Data Type Facilities, that have been universally implemented. Old features that have been superseded by new ones are not described — few of those historic features are used in modern programs although most have been retained in the language to maintain backward compatibility. Although the current standard is Fortran 2008, even many of those features first introduced into Fortran 2003 are still being implemented. The additional features of Fortran 2003 and Fortran 2008 are described by Metcalf, Reid and Cohen.

Memory safety is the state of being protected from various software bugs and security vulnerabilities when dealing with memory access, such as buffer overflows and dangling pointers. For example, Java is said to be memory-safe because its runtime error detection checks array bounds and pointer dereferences. In contrast, C and C++ allow arbitrary pointer arithmetic with pointers implemented as direct memory addresses with no provision for bounds checking, and thus are termed memory-unsafe.

Language support for array types may include certain built-in array data types, some syntactic constructions that the programmer may use to define such types and declare array variables, and special notation for indexing array elements. For example, in the Pascal programming language, the declaration type MyTable = array [1..4,1..2] of integer, defines a new array data type called MyTable. The declaration var A: MyTable then defines a variable A of that type, which is an aggregate of eight elements, each being an integer variable identified by two indices. In the Pascal program, those elements are denoted A[1,1], A[1,2], A[2,1],… A[4,2]. Special array types are often defined by the language's standard libraries.

The computer programming languages C and Object Pascal have similar times of origin, influences, and purposes. Both were used to design their own compilers early in their lifetimes.

Intel MPX is a set of extensions to the x86 instruction set architecture. With compiler, runtime library and operating system support, Intel MPX brings increased security to software by checking pointer references whose normal compile-time intentions are maliciously exploited at runtime due to buffer overflows.

References

  1. ↑ Reese, Richard (2013). Understanding and Using C Pointers: Core Techniques for Memory Management. O'Reilly Media, Inc. p. 167. ISBN   9781449344566.


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