dtor

A destructor, often abbreviated as dtor, is a special member function in object-oriented programming that is invoked when an object's lifetime ends to release resources and perform cleanup. Destructors are closely tied to the resource management strategy of a language and are typically responsible for freeing memory, closing files, releasing handles, and other housekeeping tasks.

Timing and guarantees of destruction vary by language. In languages like C++, destruction is deterministic: a destructor is called automatically when an object goes out of scope or when delete is used on a dynamically allocated object. In garbage-collected languages, destruction timing is not guaranteed; finalizers or the garbage collector may reclaim resources at an unspecified later time, or not at all if resources are managed differently.

Common language-specific notes. In C++, a destructor is declared as ~ClassName() { ... }. In C#, finalizers use a syntax like ~ClassName() { ... } but are invoked by the runtime; they are non-deterministic. In D, destructors are defined as ~this() { ... }. In Rust, the equivalent concept is the Drop trait: impl Drop for Type { fn drop(&mut self) { ... } }, which runs when a value is about to be deallocated.

Best practices and considerations. Destructors should perform minimal, non-throwing cleanup and should avoid performing actions that may fail or depend on other program state during teardown. They are commonly used within RAII (Resource Acquisition Is Initialization) patterns, tying resource lifetime to object lifetime. Be mindful of the destruction order: in many languages, member resources are released after the destructor body completes, and base-class or member destructors run in a defined order.

See also: resource management, RAII, finalizer, drop.