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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. [ 1 ] Unreachable code is sometimes also called dead code , [ 2 ] [ 3 ] although dead code may also refer to code that is executed but has no effect on ...
Exceptions are defined by different layers of a computer system, and the typical layers are CPU-defined interrupts, operating system (OS)-defined signals, programming language-defined exceptions. Each layer requires different ways of exception handling although they may be interrelated, e.g. a CPU interrupt could be turned into an OS signal.
The implementation of exception handling in programming languages typically involves a fair amount of support from both a code generator and the runtime system accompanying a compiler. (It was the addition of exception handling to C++ that ended the useful lifetime of the original C++ compiler, Cfront . [ 18 ] )
PHP generally follows C syntax, with exceptions and enhancements for its main use in web development, which makes heavy use of string manipulation. PHP variables must be prefixed by " $ ". This allows PHP to perform string interpolation in double quoted strings, where backslash is supported as an escape character .
Like buffer-overflow bugs, dangling/wild pointer bugs frequently become security holes. For example, if the pointer is used to make a virtual function call, a different address (possibly pointing at exploit code) may be called due to the vtable pointer being overwritten. Alternatively, if the pointer is used for writing to memory, some other ...
Using these exceptions to handle specific errors that arise to continue the program is called coding by exception. This anti-pattern can quickly degrade software in performance and maintainability. Executing code even after the exception is raised resembles the goto method in many software languages, which is also considered poor practice.
Most assembly languages will have a macro instruction or an interrupt address available for the particular system to intercept events such as illegal op codes, program check, data errors, overflow, divide by zero, and other such. IBM and Univac mainframes had the STXIT macro.