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Shadow Memory
In computing, shadow memory is a technique used to track and store information on computer memory used by a program during its execution. Shadow memory consists of shadow bytes that map to individual bits or one or more bytes in main memory. These shadow bytes are typically invisible to the original program and are used to record information about the original piece of data. Technique The technique is utilized by memory-error checkers that can store information on which parts of memory have been allocated to the program being checked. This shadow memory is then used for detecting and reporting incorrect accesses of memory, even though the program may not be crashing due to a segmentation fault or similar. An error checker may also store additional information on memory such as which bits have been defined and which ones do not. Memcheck, part of the Valgrind suite, uses this to detect undefined behavior resulting from acting on or printing undefined memory values. Use of shadow m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computing
Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes, and development of both hardware and software. Computing has scientific, engineering, mathematical, technological and social aspects. Major computing disciplines include computer engineering, computer science, cybersecurity, data science, information systems, information technology and software engineering. The term "computing" is also synonymous with counting and calculating. In earlier times, it was used in reference to the action performed by mechanical computing machines, and before that, to human computers. History The history of computing is longer than the history of computing hardware and includes the history of methods intended for pen and paper (or for chalk and slate) with or without the aid of tables. Computing is intimately tied to the representation of numbers, though mathematical conc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Memory
In computing, memory is a device or system that is used to store information for immediate use in a computer or related computer hardware and digital electronic devices. The term ''memory'' is often synonymous with the term ''primary storage'' or '' main memory''. An archaic synonym for memory is store. Computer memory operates at a high speed compared to storage that is slower but less expensive and higher in capacity. Besides storing opened programs, computer memory serves as disk cache and write buffer to improve both reading and writing performance. Operating systems borrow RAM capacity for caching so long as not needed by running software. If needed, contents of the computer memory can be transferred to storage; a common way of doing this is through a memory management technique called ''virtual memory''. Modern memory is implemented as semiconductor memory, where data is stored within memory cells built from MOS transistors and other components on an integrated c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Program
A computer program is a sequence or set of instructions in a programming language for a computer to execute. Computer programs are one component of software, which also includes documentation and other intangible components. A computer program in its human-readable form is called source code. Source code needs another computer program to execute because computers can only execute their native machine instructions. Therefore, source code may be translated to machine instructions using the language's compiler. ( Assembly language programs are translated using an assembler.) The resulting file is called an executable. Alternatively, source code may execute within the language's interpreter. If the executable is requested for execution, then the operating system loads it into memory and starts a process. The central processing unit will soon switch to this process so it can fetch, decode, and then execute each machine instruction. If the source code is requested for execution, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Segmentation Fault
In computing, a segmentation fault (often shortened to segfault) or access violation is a fault, or 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 will, in response, usually perform some corrective action, generally passing the fault on to the offending process by sending the process a 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), and sometimes a core dump. Segmentation faults are a common class of error in programs written in languages like C that provide low-level memory access and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Memcheck
Valgrind () is a programming tool for memory debugging, memory leak detection, and profiling. Valgrind was originally designed to be a free memory debugging tool for Linux on x86, but has since evolved to become a generic framework for creating dynamic analysis tools such as checkers and profilers. Overview Valgrind is in essence a virtual machine using just-in-time compilation techniques, including dynamic recompilation. Nothing from the original program ever gets run directly on the host processor. Instead, Valgrind first translates the program into a temporary, simpler form called intermediate representation (IR), which is a processor-neutral, static single assignment form-based form. After the conversion, a tool (see below) is free to do whatever transformations it would like on the IR, before Valgrind translates the IR back into machine code and lets the host processor run it. Valgrind recompiles binary code to run on host and target (or simulated) CPUs of the same architec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Valgrind
Valgrind () is a programming tool for memory debugging, memory leak detection, and profiling. Valgrind was originally designed to be a free memory debugging tool for Linux on x86, but has since evolved to become a generic framework for creating dynamic analysis tools such as checkers and profilers. Overview Valgrind is in essence a virtual machine using just-in-time compilation techniques, including dynamic recompilation. Nothing from the original program ever gets run directly on the host processor. Instead, Valgrind first translates the program into a temporary, simpler form called intermediate representation (IR), which is a processor-neutral, static single assignment form-based form. After the conversion, a tool (see below) is free to do whatever transformations it would like on the IR, before Valgrind translates the IR back into machine code and lets the host processor run it. Valgrind recompiles binary code to run on host and target (or simulated) CPUs of the same archit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Race
A race condition or race hazard is the condition of an electronics, software, or other system where the system's substantive behavior is dependent on the sequence or timing of other uncontrollable events. It becomes a bug when one or more of the possible behaviors is undesirable. The term ''race condition'' was already in use by 1954, for example in David A. Huffman's doctoral thesis "The synthesis of sequential switching circuits". Race conditions can occur especially in logic circuits, multithreaded, or distributed software programs. In electronics A typical example of a race condition may occur when a logic gate combines signals that have traveled along different paths from the same source. The inputs to the gate can change at slightly different times in response to a change in the source signal. The output may, for a brief period, change to an unwanted state before settling back to the designed state. Certain systems can tolerate such glitches but if this output function ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AddressSanitizer
AddressSanitizer (or ASan) is an open source programming tool that detects memory corruption bugs such as buffer overflows or accesses to a dangling pointer (use-after-free). AddressSanitizer is based on compiler instrumentation and directly mapped shadow memory. AddressSanitizer is currently implemented in Clang (starting from version 3.1), GCC (starting from version 4.8), Xcode (starting from version 7.0) and MSVC (widely available starting from version 16.9). On average, the instrumentation increases processing time by about 73% and memory usage by 240%. Users Chromium and Firefox developers are active users of AddressSanitizer; the tool has found hundreds of bugs in these web browsers. A number of bugs were found in FFmpeg and FreeType. The Linux kernel has enabled the AddressSanitizer for the x86-64 architecture as of Linux version 4.0. KernelAddressSanitizer The KernelAddressSanitizer (KASAN) detects dynamic memory errors in the Linux kernel. Kernel instrumentation re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clang
Clang is a compiler front end for the C, C++, Objective-C, and Objective-C++ programming languages, as well as the OpenMP, OpenCL, RenderScript, CUDA, and HIP frameworks. It acts as a drop-in replacement for the GNU Compiler Collection (GCC), supporting most of its compilation flags and unofficial language extensions. It includes a static analyzer, and several code analysis tools. Clang operates in tandem with the LLVM compiler back end and has been a subproject of LLVM 2.6 and later. As with LLVM, it is free and open-source software under the Apache License 2.0 software license. Its contributors include Apple, Microsoft, Google, ARM, Sony, Intel, and AMD. Clang 14, the latest major version of Clang as of March 2022, has full support for all published C++ standards up to C++17, implements most features of C++20, and has initial support for the upcoming C++23 standard. Since v6.0.0, Clang compiles C++ using the GNU++14 dialect by default, which includes features from the C+ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binary Translation
In computing, binary translation is a form of binary recompilation where sequences of instructions are translated from a ''source'' instruction set to the ''target'' instruction set. In some cases such as instruction set simulation, the target instruction set may be the same as the source instruction set, providing testing and debugging features such as instruction trace, conditional breakpoints and hot spot detection. The two main types are static and dynamic binary translation. Translation can be done in hardware (for example, by circuits in a CPU) or in software (e.g. run-time engines, static recompiler, emulators). Motivation Binary translation is motivated by a lack of a binary for a target platform, the lack of source code to compile for the target platform, or otherwise difficulty in compiling the source for the target platform. Statically-recompiled binaries run potentially faster than their respective emulated binaries, as the emulation overhead is removed. This ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Instrumentation (computer Programming)
In the context of computer programming, instrumentation refers to the measure of a product's performance, in order to diagnose errors and to write trace information. Instrumentation can be of two types: source instrumentation and binary instrumentation. Output In programming, instrumentation means: * Profiling: measuring dynamic program behaviors during a training run with a representative input. This is useful for properties of a program that cannot be analyzed statically with sufficient precision, such as alias analysis. * Inserting timers into functions. * Logging major events such as crashes. Limitations Instrumentation is limited by execution coverage. If the program never reaches a particular point of execution, then instrumentation at that point collects no data. For instance, if a word processor application is instrumented, but the user never activates the print feature, then the instrumentation can say nothing about the routines which are used exclusively by th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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