Deallocate

Deallocate is a verb meaning to release or free resources that were previously allocated. In computing, deallocation is a core part of memory management, referring to returning memory or other resources to the system so they can be reused.

Memory deallocation can be explicit or implicit. In languages with manual memory management, such as C, developers must explicitly deallocate memory using functions like free, or delete objects as appropriate. Failure to do so can cause memory leaks, while deallocating a resource more than once can lead to undefined behavior.

In C++, lifetime management is often tied to scope, with destructors performing deallocation automatically when objects go out of scope. In languages with automatic garbage collection, such as Java or C#, deallocation occurs when objects become unreachable, though timing is non-deterministic.

Deallocation also applies to resources beyond memory, including file descriptors, network sockets, buffers, and handles to devices or graphics resources. Releasing these resources promptly helps prevent exhaustion and improves system stability.

Common pitfalls include double frees, use-after-free errors in manual management, and unnecessary retention in managed languages that prolong lifetimes and waste memory. Effective deallocation strategies include scope-based resource management and deterministic destruction.

Related terms include memory allocation, free, and garbage collection.