Do Built-In Types Exhibit Move Semantics?

Built-In Types and Move Semantics: Demystifying Undefined Behavior

In programming, move semantics refer to the efficient transfer of resources from one object to another, often by avoiding unnecessary copies and maintaining the validity of both objects. However, a common question arises: "Do built-in types possess move semantics?"

Contrary to conventional logic, built-in types, such as integers and characters, do not inherently hold any resources that can be transferred. Their value is the resource itself. Thus, the concept of transferring ownership for built-in types is effectively null.

The behavior demonstrated in the code example where "Func" modifies the value of "num" is a result of passing the r-value reference (a reference to a temporary object) to the function. This allows the modification of the value through the reference, but it does not constitute true move semantics.

The mechanism responsible for move semantics is found in move constructors and move assignment operators. These operators copy the resources from the source object to the target object, effectively transferring the ownership. Built-in types, lacking such operators, rely solely on copies when passed by value, not moves.

The confusion stems from the functionality of "std::move," which converts l-value references (objects with known addresses) into x-value references (objects residing in temporary memory). It enables the binding of r-value references but does not trigger any move operations.

In summary, built-in types do not possess true move semantics as they lack the mechanisms necessary for resource transfer. The behavior observed in the code example is a consequence of passing an r-value reference and modifying the original object through it, not a result of move semantics.

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