Hermes [1] [2] is a language for distributed programming [3] that was developed at IBM's Thomas J. Watson Research Center from 1986 through 1992, with an open-source compiler and run-time system. [4] Hermes' primary features included: [5]
It used typestate analysis to check variables transitions errors, to rule out some semantically non meaningful transitions from one state to another (i.e. starting from a value, some sequences of operations on a variable are nonsensical), of which reading an uninitialized variable is a special case. In this role of compile-time checking of data initialization is similar to definite assignment analysis performed by Java, Cyclone and C#.
Hermes and its predecessor, NIL (Network Implementation Language), were the earliest programming languages supporting this form of initialization checking. [6] Typestate was actually used more extensively, to generate compiler-inserted "delete" operations.
Ada is a structured, statically typed, imperative, and object-oriented high-level programming language, extended from Pascal and other languages. It has built-in language support for design by contract (DbC), extremely strong typing, explicit concurrency, tasks, synchronous message passing, protected objects, and non-determinism. Ada improves code safety and maintainability by using the compiler to find errors in favor of runtime errors. Ada is an international technical standard, jointly defined by the International Organization for Standardization (ISO), and the International Electrotechnical Commission (IEC). As of 2020, the standard, called Ada 2012 informally, is ISO/IEC 8652:2012.
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—also called garbage. Garbage collection was invented by American computer scientist John McCarthy around 1959 to simplify manual memory management in Lisp.
In computer science, reference counting is a programming technique of storing the number of references, pointers, or handles to a resource, such as an object, a block of memory, disk space, and others.
In computing, a virtual machine (VM) is the virtualization/emulation of a computer system. Virtual machines are based on computer architectures and provide functionality of a physical computer. Their implementations may involve specialized hardware, software, or a combination.
In computing, just-in-time (JIT) compilation is a way of executing computer code that involves compilation during execution of a program rather than before execution. Most often, this consists of source code or more commonly bytecode translation to machine code, which is then executed directly. A system implementing a JIT compiler typically continuously analyses the code being executed and identifies parts of the code where the speedup gained from compilation or recompilation would outweigh the overhead of compiling that code.
In compiler optimization, register allocation is the process of assigning a large number of target program variables onto a small number of CPU registers.
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.
Ralph E. Griswold was a computer scientist known for his research into high-level programming languages and symbolic computation. His language credits include the string processing language SNOBOL, SL5, and Icon.
Data-flow analysis is a technique for gathering information about the possible set of values calculated at various points in a computer program. A program's control-flow graph (CFG) is used to determine those parts of a program to which a particular value assigned to a variable might propagate. The information gathered is often used by compilers when optimizing a program. A canonical example of a data-flow analysis is reaching definitions.
In computer science, pointer analysis, or points-to analysis, is a static code analysis technique that establishes which pointers, or heap references, can point to which variables, or storage locations. It is often a component of more complex analyses such as escape analysis. A closely related technique is shape analysis.
Thread Level Speculation (TLS) is a technique to speculatively execute a section of computer code that is anticipated to be executed later in parallel with the normal execution on a separate independent thread. Such a speculative thread may need to make assumptions about the values of input variables. If these prove to be invalid the speculative thread will need to be discarded and squashed. If the assumptions are correct the program can complete in a shorter time provided the thread was able to be scheduled efficiently.
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 potentially memory-unsafe.
In computer science, false sharing is a performance-degrading usage pattern that can arise in systems with distributed, coherent caches at the size of the smallest resource block managed by the caching mechanism. When a system participant attempts to periodically access data that is not being altered by another party, but those data share a cache block with data that are being altered, the caching protocol may force the first participant to reload the whole cache block despite a lack of logical necessity. The caching system is unaware of activity within this block and forces the first participant to bear the caching system overhead required by true shared access of a resource.
In computer programming and software development, debugging is the process of finding and resolving bugs within computer programs, software, or systems.
In computer science, region-based memory management is a type of memory management in which each allocated object is assigned to a region. A region, also called a zone, arena, area, or memory context, is a collection of allocated objects that can be efficiently deallocated all at once. Like stack allocation, regions facilitate allocation and deallocation of memory with low overhead; but they are more flexible, allowing objects to live longer than the stack frame in which they were allocated. In typical implementations, all objects in a region are allocated in a single contiguous range of memory addresses, similarly to how stack frames are typically allocated.
Tracing just-in-time compilation is a technique used by virtual machines to optimize the execution of a program at runtime. This is done by recording a linear sequence of frequently executed operations, compiling them to native machine code and executing them. This is opposed to traditional just-in-time (JIT) compilers that work on a per-method basis.
Typestate analysis, sometimes called protocol analysis, is a form of program analysis employed in programming languages. It is most commonly applied to object-oriented languages. Typestates define valid sequences of operations that can be performed upon an instance of a given type. Typestates, as the name suggests, associate state information with variables of that type. This state information is used to determine at compile-time which operations are valid to be invoked upon an instance of the type. Operations performed on an object that would usually only be executed at run-time are performed upon the type state information which is modified to be compatible with the new state of the object.
Kathryn S. McKinley is an American computer scientist noted for her research on compilers, runtime systems, and computer architecture. She is also known for her leadership in broadening participation in computing. McKinley was co-chair of CRA-W from 2011 to 2014.
Gradual typing is a type system in which some variables and expressions may be given types and the correctness of the typing is checked at compile time and some expressions may be left untyped and eventual type errors are reported at runtime. Gradual typing allows software developers to choose either type paradigm as appropriate, from within a single language. In many cases gradual typing is added to an existing dynamic language, creating a derived language allowing but not requiring static typing to be used. In some cases a language uses gradual typing from the start.
David Bacon is an American computer programmer.