Bila hendak menggunakan Rujukan Pass by Value vs Pass by Rvalue dalam C ?

Kerumitan Pass by Value dan Pass by Rvalue Rujukan

Pengenalan:

Dalam C , pilihan antara pas mengikut nilai atau lulus rujukan rnilai boleh memberi kesan ketara kepada semantik dan kecekapan fungsi. Memahami perbezaan antara kedua-dua mekanisme lulus parameter ini adalah penting untuk menulis kod yang berkesan dan berprestasi.

Lulus Mengikut Nilai vs Lulus Rujukan Nilai R

Pengisytiharan Parameter:

Lewati Nilai:

<code class="cpp">void foo(Widget w);
````

**Pass by Rvalue Reference:**</code>

void foo(Widget&& w);

#### Ownership Semantics:

* **Pass by Value:** Caller's object is copied into the function, and the copy is destroyed when the function exits. Ownership is transferred to the function.
* **Pass by Rvalue Reference:** Caller's object is moved into the function, and the caller relinquishes ownership. The moved object's resources are directly accessed within the function.

#### Implications for Interface:

* Pass by value implies that the caller expects the object to remain unchanged.
* Pass by rvalue reference suggests that the function may modify or destroy the object.

**Efficiency:**

* Pass by rvalue reference is potentially more efficient because it eliminates the need for an additional copy.
* Pass by value may result in a single move or copy constructor call, depending on the compiler's optimization level.

**Explicitness:**

* Pass by rvalue reference forces the caller to explicitly move the argument into the function, making the transfer of ownership clear.
* Pass by value implicitly copies the argument, which can lead to unexpected behavior if the intention is to move ownership.

### Conclusion:

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