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Heap Allocation
In computer science, manual memory management refers to the usage of manual instructions by the programmer to identify and deallocate unused objects, or garbage. Up until the mid-1990s, the majority of programming languages used in industry supported manual memory management, though garbage collection has existed since 1959, when it was introduced with Lisp. Today, however, languages with garbage collection such as Java are increasingly popular and the languages Objective-C and Swift provide similar functionality through Automatic Reference Counting. The main manually managed languages still in widespread use today are C and C++ – see C dynamic memory allocation. Description Many programming languages use manual techniques to determine when to ''allocate'' a new object from the free store. C uses the malloc function; C++ and Java use the new operator; and many other languages (such as Python) allocate all objects from the free store. Determining when an object ought to be cr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Science
Computer science is the study of computation, information, and automation. Computer science spans Theoretical computer science, theoretical disciplines (such as algorithms, theory of computation, and information theory) to Applied science, applied disciplines (including the design and implementation of Computer architecture, hardware and Software engineering, software). Algorithms and data structures are central to computer science. The theory of computation concerns abstract models of computation and general classes of computational problem, problems that can be solved using them. The fields of cryptography and computer security involve studying the means for secure communication and preventing security vulnerabilities. Computer graphics (computer science), Computer graphics and computational geometry address the generation of images. Programming language theory considers different ways to describe computational processes, and database theory concerns the management of re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Local Variable
In computer science, a local variable is a variable that is given ''local scope''. A local variable reference in the function or block in which it is declared overrides the same variable name in the larger scope. In programming languages with only two levels of visibility, local variables are contrasted with global variables. On the other hand, many ALGOL-derived languages allow any number of nested levels of visibility, with private variables, functions, constants and types hidden within them, either by nested blocks or nested functions. Local variables are fundamental to procedural programming, and more generally modular programming: variables of local scope are used to avoid issues with side-effects that can occur with global variables. Scope Local variables may have a lexical or dynamic scope, though lexical (static) scoping is far more common. In lexical scoping (or lexical scope; also called static scoping or static scope), if a variable name's scope is a certain blo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resource Acquisition Is Initialization
Resource acquisition is initialization (RAII) is a programming idiom used in several object-oriented, statically typed programming languages to describe a particular language behavior. In RAII, holding a resource is a class invariant, and is tied to object lifetime. Resource allocation (or acquisition) is done during object creation (specifically initialization), by the constructor, while resource deallocation (release) is done during object destruction (specifically finalization), by the destructor. In other words, resource acquisition must succeed for initialization to succeed. Thus, the resource is guaranteed to be held between when initialization finishes and finalization starts (holding the resources is a class invariant), and to be held only when the object is alive. Thus, if there are no object leaks, there are no resource leaks. RAII is associated most prominently with C++, where it originated, but also Ada, Vala, and Rust. The technique was developed for exception ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resource Management (computing)
In computer programming, resource management refers to techniques for managing resources (components with limited availability). Computer programs may manage their own resources by using features exposed by programming languages ( is a survey article contrasting different approaches), or may elect to manage them by a host – an operating system or virtual machine – or another program. Host-based management is known as ''resource tracking,'' and consists of cleaning up resource leaks: terminating access to resources that have been acquired but not released after use. This is known as ''reclaiming'' resources, and is analogous to garbage collection for memory. On many systems, the operating system reclaims resources after the process makes the exit system call. Controlling access The omission of releasing a resource when a program has finished using it is known as a resource leak, and is an issue in sequential computing. Multiple processes wish to access a limited resource c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wild Pointer
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. Dangling pointers arise during object destruction, when an object that is pointed to by a given pointer is deleted or deallocated, without modifying the value of that said pointer, so that the pointer still points to the memory location of the deallocated memory. The system may reallocate the previously freed memory, and if the program then dereferences the (now) dangling pointer, '' unpredictable behavior may result'', as the memory may now contain completely different data. If the program writes to memory referenced by a dangling pointer, a silent corruption of unrelated data may result, leading to subtle bugs that can be extremely difficult to find. If the memory has been realloc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Undefined Behavior
In computer programming, a program exhibits undefined behavior (UB) when it contains, or is executing code for which its programming language specification does not mandate any specific requirements. This is different from unspecified behavior, for which the language specification does not prescribe a result, and implementation-defined behavior that defers to the documentation of another component of the platform (such as the ABI or the translator documentation). In the C programming community, undefined behavior may be humorously referred to as "nasal demons", after a comp.std.c post that explained undefined behavior as allowing the compiler to do anything it chooses, even "to make demons fly out of your nose". Overview Some programming languages allow a program to operate differently or even have a different control flow from the source code, as long as it exhibits the same user-visible side effects, ''if undefined behavior never happens during program execution''. Undef ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Memory Protection
Memory protection is a way to control memory access rights on a computer, and is a part of most modern instruction set architectures and operating systems. The main purpose of memory protection is to prevent a process from accessing memory that has not been allocated to it. This prevents a bug or malware within a process from affecting other processes, or the operating system itself. Protection may encompass all accesses to a specified area of memory, write accesses, or attempts to execute the contents of the area. An attempt to access unauthorized memory results in a hardware fault, e.g., a segmentation fault, storage violation exception, generally causing abnormal termination of the offending process. Memory protection for computer security includes additional techniques such as address space layout randomization and executable-space protection. Methods Segmentation Segmentation refers to dividing a computer's memory into segments. A reference to a memory locatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Segmentation Fault
In computing, a segmentation fault (often shortened to segfault) or access violation is a Interrupt, failure condition raised by hardware with memory protection, notifying an operating system (OS) the software has attempted to access a restricted area of memory (a memory access violation). On standard x86 computers, this is a form of general protection fault. The operating system kernel (operating system), kernel will, in response, usually perform some corrective action, generally passing the fault on to the offending Process (computing), process by sending the process a signal (IPC), signal. Processes can in some cases install a custom signal handler, allowing them to recover on their own,''Expert C programming: deep C secrets'' By Peter Van der Linden, page 188 but otherwise the OS default signal handler is used, generally causing abnormal termination of the process (a program Crash (computing), crash), and sometimes a core dump. Segmentation faults are a common class of error i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heap Corruption
Memory corruption occurs in a computer program when the contents of a memory location are modified due to programmatic behavior that exceeds the intention of the original programmer or program/language constructs; this is termed as violation of memory safety. The most likely causes of memory corruption are programming errors (software bugs). When the corrupted memory contents are used later in that program, it leads either to program crash or to strange and bizarre program behavior. Nearly 10% of application crashes on Windows systems are due to heap corruption.{{Cite web, last=Radich, first=Q., last2=Sherer, first2=T., last3=Sharkey, first3=K., last4=Batchelor, first4=D., last5=Kennedy, first5=J. T., last6=Mabee, first6=D., last7=Coulter, first7=D., last8=Michael, first8=S., date=28 April 2021, title=Application Verifier (Windows 7 and Windows Server 2008 R2 Application Quality Cookbook) - Win32 apps, publisher=Microsoft Developer Network, url=https://docs.microsoft.com/en-us/wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamic Memory Management
Memory management (also dynamic memory management, dynamic storage allocation, or dynamic memory allocation) is a form of resource management applied to computer memory. The essential requirement of memory management is to provide ways to dynamically allocate portions of memory to programs at their request, and free it for reuse when no longer needed. This is critical to any advanced computer system where more than a single process might be underway at any time. Several methods have been devised that increase the effectiveness of memory management. Virtual memory systems separate the memory addresses used by a process from actual physical addresses, allowing separation of processes and increasing the size of the virtual address space beyond the available amount of RAM using paging or swapping to secondary storage. The quality of the virtual memory manager can have an extensive effect on overall system performance. The system allows a computer to appear as if it may have more me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operating System
An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for efficient use of the system and may also include accounting software for cost allocation of Scheduling (computing), processor time, mass storage, peripherals, and other resources. For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by it. Operating systems are found on many devices that contain a computerfrom cellular phones and video game consoles to web servers and supercomputers. , Android (operating system), Android is the most popular operating system with a 46% market share, followed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Security Bug
A security bug or security defect is a software bug that can be exploited to gain unauthorized access or privileges on a computer system. Security bugs introduce security vulnerabilities by compromising one or more of: * Authentication of users and other entities * Authorization of access rights and privileges * Data confidentiality * Data integrity Security bugs do not need be identified nor exploited to be qualified as such and are assumed to be much more common than known vulnerabilities in almost any system. Causes Security bugs, like all other software bugs, stem from root causes that can generally be traced to either absent or inadequate: * Software developer training * Use case analysis * Software engineering methodology * Quality assurance testing * and other best practices Taxonomy Security bugs generally fall into a fairly small number of broad categories that include: * Memory safety (e.g. buffer overflow and dangling pointer bugs) * Race condition * Secure ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
