在 C 中何時使用按值傳遞與按右值參考傳遞？

以值傳遞與右值引用傳遞的複雜度

簡介：

在C 中，pass 之間的選擇按值或按右值引用傳遞可以顯著影響函數的語意和效率。了解這兩種參數傳遞機制之間的差異對於編寫有效且高效能的程式碼至關重要。

按值傳遞與按右值引用傳遞

參數聲明：

以值傳遞：

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

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

按值傳遞：

#### 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:

>void foo(Widget&& w);

以上是在 C 中何時使用按值傳遞與按右值參考傳遞？的詳細內容。更多資訊請關注PHP中文網其他相關文章！