nonPOD

nonPOD refers to types in C++ that are not Plain Old Data (POD). POD types are simple, with a stable memory layout and trivial copy, move, and destruction semantics. nonPOD types do not satisfy these criteria and may have non-trivial constructors or destructors, virtual functions, non-standard layouts, or other features that affect their binary representation and copying behavior.

In practice, nonPOD includes classes or structs that have user-provided or non-trivial constructors or destructors, virtual methods, non-trivial copy or move operations, or non-standard-layout members. Such types may rely on runtime initialization, have vtables, or enforce invariants that must be maintained by constructors. Because of these characteristics, their in-memory layout is not guaranteed to be portable across compilers or platforms.

Consequences for code use include the inability to safely apply raw memory operations such as memcpy to nonPOD objects, and the need to follow proper construction, destruction, and copying semantics. Serialization, cloning, or deep copying typically requires explicit logic or dedicated libraries rather than relying on binary copying. When performance or binary compatibility is a concern, developers often differentiate between POD (or trivially copyable and standard-layout types in modern terminology) and nonPOD types to choose appropriate techniques.

Modern terminology in C++ tends to use a refinement of POD, including concepts like standard-layout and trivially copyable types. NonPOD remains a catchall for types that do not meet those criteria, including many user-defined classes with non-trivial semantics. Understanding whether a type is POD or nonPOD helps guide memory handling, serialization, and interoperability decisions.