|
Shadow Memory
In computing, shadow memory is a technique used to track and store information on computer memory used by a computer program, 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. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computing
Computing is any goal-oriented activity requiring, benefiting from, or creating computer, computing machinery. It includes the study and experimentation of algorithmic processes, and the development of both computer hardware, 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 calculation, calculating. In earlier times, it was used in reference to the action performed by Mechanical computer, mechanical computing machines, and before that, to Computer (occupation), 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. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Memory
Computer memory stores information, such as data and programs, for immediate use in the computer. The term ''memory'' is often synonymous with the terms ''RAM,'' ''main memory,'' or ''primary storage.'' Archaic synonyms for main memory include ''core'' (for magnetic core memory) and ''store''. Main memory operates at a high speed compared to mass storage which is slower but less expensive per bit and higher in capacity. Besides storing opened programs and data being actively processed, computer memory serves as a Page cache, mass storage cache and write buffer to improve both reading and writing performance. Operating systems borrow RAM capacity for caching so long as it is 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 computer memory is implemented as semiconductor memory, where data is stored within memory cell (com ... [...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 Execution (computing), execute. It is one component of software, which also includes software documentation, documentation and other intangible components. A ''computer program'' in its human-readable form is called source code. Source code needs another computer program to Execution (computing), execute because computers can only execute their native machine instructions. Therefore, source code may be Translator (computing), translated to machine instructions using a compiler written for the language. (Assembly language programs are translated using an Assembler (computing), assembler.) The resulting file is called an executable. Alternatively, source code may execute within an interpreter (computing), interpreter written for the language. If the executable is requested for execution, then the operating system Loader (computing), loads it into Random-access memory, memory and ... [...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] |
Memcheck
Valgrind () is a programming tool for memory debugging, memory leak detection, and profiling. Valgrind was originally designed to be a freely licensed 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 s ... [...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 freely licensed 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 t ... [...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, leading to unexpected or inconsistent results. 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 or multithreaded or distributed software programs. Using mutual exclusion can prevent race conditions in distributed software systems. 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 t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AddressSanitizer
A code sanitizer is a programming tool that detects bugs in the form of undefined or suspicious behavior by a compiler inserting instrumentation code at runtime. The class of tools was first introduced by Google's AddressSanitizer (or ASan) of 2012, which uses directly mapped shadow memory to detect memory corruption such as buffer overflows or accesses to a dangling pointer (use-after-free). AddressSanitizer Google's ASan, introduced in 2012, uses a shadow memory scheme to detect memory bugs. It is available in: * Clang (starting from version 3.1) * GCC (starting from version 4.8) * Xcode (starting from version 7.0) * MSVC (widely available starting from version 16.9). On average, the instrumentation increases processing time by about 73% and memory usage by 240%. There is a hardware-accelerated ASan called HWAsan available for AArch64 and (in a limited fashion) x86_64. AddressSanitizer does not detect any uninitialized memory reads (but this is detected by MemorySanitizer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clang
Clang () is a compiler front end for the programming languages C, C++, Objective-C, Objective-C++, and the software frameworks OpenMP, OpenCL, RenderScript, CUDA, SYCL, and HIP. It acts as a drop-in replacement for the GNU Compiler Collection (GCC), supporting most of its compiling 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 2.0 software license. Its contributors include Apple, Microsoft, Google, ARM, Sony, Intel, and AMD. Clang 17, the latest major version of Clang as of October 2023, has full support for all published C++ standards up to C++17, implements most features of C++20, and has initial support for the C++23 standard. Since v16.0.0, Clang compiles C++ using the GNU++17 dialect by default, which includes features fro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binary Translation
In computing, binary translation is a form of binary recompilation where sequences of instruction (computer science), instructions are translated from a source instruction set (ISA) to the target instruction set with respect to the operating system for which the binary was compiled for. In some cases such as instruction set simulator, 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 (computer science), 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, all are typically slow). 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 compi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Instrumentation (computer Programming)
In computer programming, instrumentation is the act of modifying software so that analysis can be performed on it. Generally, instrumentation either modifies source code or binary code. Execution environments like the JVM provide separate interfaces to add instrumentation to program executions, such as the JVMTI, which enables instrumentation during program start. Instrumentation enables profiling: measuring dynamic behavior during a test run. This is useful for properties of a program that cannot be analyzed statically with sufficient precision, such as performance and alias analysis. Instrumentation can include: * Logging events such as failures and operation start and end * Measuring and logging the duration of operations 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
