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An undefined variable in the source code of a computer program is a variable that is accessed in the code but has not been declared by that code. [1] In some programming languages, an implicit declaration is provided the first time such a variable is encountered at compile time. In other languages such a usage is considered to be sufficiently ...
It is the responsibility of the programmer to write code that never invokes undefined behavior, although compiler implementations are allowed to issue diagnostics when this happens. Compilers nowadays have flags that enable such diagnostics, for example, -fsanitize=undefined enables the "undefined behavior sanitizer" in gcc 4.9 [2] and in clang ...
Program execution; General concepts; Code; Translation. Compiler. Compile time; Optimizing compiler; Intermediate representation (IR); Execution. Runtime system. Runtime
For example, a precondition—an assertion placed at the beginning of a section of code—determines the set of states under which the programmer expects the code to execute. A postcondition—placed at the end—describes the expected state at the end of execution. For example: x > 0 { x++ } x > 1.
C does not provide direct support to exception handling: it is the programmer's responsibility to prevent errors in the first place and test return values from the functions.
The earliest published JIT compiler is generally attributed to work on LISP by John McCarthy in 1960. [4] In his seminal paper Recursive functions of symbolic expressions and their computation by machine, Part I, he mentions functions that are translated during runtime, thereby sparing the need to save the compiler output to punch cards [5] (although this would be more accurately known as a ...
In C++ run time checking is not part of the language, but part of the STL and is enabled with a compiler switch (_GLIBCXX_DEBUG=1 or _LIBCPP_DEBUG=1). C# also supports unsafe regions: sections of code that (among other things) temporarily suspend bounds checking to raise efficiency. These are useful for speeding up small time-critical ...
The broad field of runtime verification methods can be classified by three dimensions: [9] The system can be monitored during the execution itself (online) or after the execution e.g. in form of log analysis (offline). The verifying code is integrated into the system (as done in Aspect-oriented Programming) or is provided as an external entity.