|
Dead Store
In computer programming, a local variable that is assigned a value but is not read by any subsequent instruction is referred to as a dead store. Dead stores waste processor time and memory, and may be detected through the use of static program analysis, and removed by an optimizing compiler. If the purpose of a store is intentionally to overwrite data, for example when a password is being removed from memory, dead store optimizations can cause the write not to happen, leading to a security issue. Some system libraries have specific functions designed to avoid such dangerous optimizations, e.g. explicit_bzero on OpenBSD. Examples Java example of a dead store: // DeadStoreExample.java import java.util.ArrayList; import java.util.Arrays; import java.util.List; public class DeadStoreExample In the above code an ArrayList object was instantiated but never used. Instead, in the next line the variable which references it is set to point to a different object. The ArrayList which was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Programming
Computer programming is the process of performing a particular computation (or more generally, accomplishing a specific computing result), usually by designing and building an executable computer program. Programming involves tasks such as analysis, generating algorithms, Profiling (computer programming), profiling algorithms' accuracy and resource consumption, and the implementation of algorithms (usually in a chosen programming language, commonly referred to as coding). The source code of a program is written in one or more languages that are intelligible to programmers, rather than machine code, which is directly executed by the central processing unit. The purpose of programming is to find a sequence of instructions that will automate the performance of a task (which can be as complex as an operating system) on a computer, often for solving a given problem. Proficient programming thus usually requires expertise in several different subjects, including knowledge of the Domain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Static Program Analysis
In computer science, static program analysis (or static analysis) is the analysis of computer programs performed without executing them, in contrast with dynamic program analysis, which is performed on programs during their execution. The term is usually applied to analysis performed by an automated tool, with human analysis typically being called "program understanding", program comprehension, or code review. In the last of these, software inspection and software walkthroughs are also used. In most cases the analysis is performed on some version of a program's source code, and, in other cases, on some form of its object code. Rationale The sophistication of the analysis performed by tools varies from those that only consider the behaviour of individual statements and declarations, to those that include the complete source code of a program in their analysis. The uses of the information obtained from the analysis vary from highlighting possible coding errors (e.g., the lint t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optimizing Compiler
In computing, an optimizing compiler is a compiler that tries to minimize or maximize some attributes of an executable computer program. Common requirements are to minimize a program's execution time, memory footprint, storage size, and power consumption (the last three being popular for portable computers). Compiler optimization is generally implemented using a sequence of ''optimizing transformations'', algorithms which take a program and transform it to produce a semantically equivalent output program that uses fewer resources or executes faster. It has been shown that some code optimization problems are NP-complete, or even undecidable. In practice, factors such as the programmer's willingness to wait for the compiler to complete its task place upper limits on the optimizations that a compiler might provide. Optimization is generally a very CPU- and memory-intensive process. In the past, computer memory limitations were also a major factor in limiting which optimizations could ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Garbage Collection (computer Science)
In computer science, garbage collection (GC) is a form of automatic memory management. The ''garbage collector'' attempts to reclaim memory which was allocated by the program, but is no longer referenced; such memory is called '' garbage''. Garbage collection was invented by American computer scientist John McCarthy around 1959 to simplify manual memory management in Lisp. Garbage collection relieves the programmer from doing manual memory management, where the programmer specifies what objects to de-allocate and return to the memory system and when to do so. Other, similar techniques include stack allocation, region inference, and memory ownership, and combinations thereof. Garbage collection may take a significant proportion of a program's total processing time, and affect performance as a result. Resources other than memory, such as network sockets, database handles, windows, file descriptors, and device descriptors, are not typically handled by garbage collection, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dead Code
The term dead code has multiple definitions. Some use the term to refer to code (i.e. instructions in memory) which can never be executed at run-time. In some areas of computer programming, dead code is a section in the source code of a program which is executed but whose result is never used in any other computation. The execution of dead code wastes computation time and memory. While the result of a dead computation may never be used, it may raise exceptions or affect some global state, thus removal of such code may change the output of the program and introduce unintended bugs. Compiler optimizations are typically conservative in their approach to dead-code removal if there is any ambiguity as to whether removal of the dead code will affect the program output. The programmer may aid the compiler in this matter by making additional use of static and/or inline functions and enabling the use of link-time optimization. Example int foo (int iX, int iY) In the above example, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unreachable Code
In computer programming, unreachable code is part of the source code of a program which can never be executed because there exists no control flow path to the code from the rest of the program. Unreachable code is sometimes also called ''dead code'', although dead code may also refer to code that is executed but has no effect on the output of a program. Unreachable code is generally considered undesirable for several reasons: * It uses memory unnecessarily * It can cause unnecessary use of the CPU's instruction cache ** This can also decrease data locality * Time and effort may be spent testing, maintaining and documenting code which is never used ** Sometimes an automated test is the only thing using the code. However, unreachable code can have some legitimate uses, like providing a library of functions for calling or jumping to manually via a debugger while the program is halted after a breakpoint. This is particularly useful for examining and pretty-printing the internal st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Compiler Optimizations
In computing, an optimizing compiler is a compiler that tries to minimize or maximize some attributes of an executable computer program. Common requirements are to minimize a program's execution time, memory footprint, storage size, and power consumption (the last three being popular for portable computers). Compiler optimization is generally implemented using a sequence of ''optimizing transformations'', algorithms which take a program and transform it to produce a semantically equivalent output program that uses fewer resources or executes faster. It has been shown that some code optimization problems are NP-complete, or even undecidable. In practice, factors such as the programmer's willingness to wait for the compiler to complete its task place upper limits on the optimizations that a compiler might provide. Optimization is generally a very CPU- and memory-intensive process. In the past, computer memory limitations were also a major factor in limiting which optimizations could ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Software Anomalies
Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consists of machine language instructions supported by an individual processor—typically a central processing unit (CPU) or a graphics processing unit (GPU). Machine language consists of groups of binary values signifying processor instructions that change the state of the computer from its preceding state. For example, an instruction may change the value stored in a particular storage location in the computer—an effect that is not directly observable to the user. An instruction may also invoke one of many input or output operations, for example displaying some text on a computer screen; causing state changes which should be visible to the user. The processor executes the instructions in the order they are provided, unless it is instructed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.svg "Click for more on -> Software Anomalies")