How Can I Efficiently Expand a C Vector Using Move Semantics?

Efficiently Expanding a Vector with Move Semantics

When handling a vector of non-trivial objects, you may desire to enforce the use of the move constructor when the vector grows.

In C , a vector typically employs copy constructors to instantiate new elements when it expands. However, to leverage the move constructor and its performance benefits, it's essential to explicitly inform std::vector that the move constructor is safe and exception-proof.

To achieve this, declare the move constructor as noexcept, ensuring to std::vector that it will not throw exceptions. For instance:

A(A &&rhs) noexcept {
  // Perform move operations...
}

By ensuring noexcept behavior, std::vector is confident to utilize the move constructor without violating exception guarantees.

Alternatively, you can explicitly request default move semantics by declaring:

A(A &&rhs) = default;

This approach will automatically generate a noexcept move constructor when possible.

However, if the move constructor is not noexcept, std::vector cannot invoke it since it cannot guarantee exception safety as per the C standard.

Note that earlier versions of Visual Studio 2015 and older may not fully support this approach despite supporting move semantics.

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