When Should You Use `= default` for Default Constructors in C 11?

The Advantages of "= default" in C 11

In C 11, the "= default" syntax allows you to explicitly indicate that you want the compiler to generate a default constructor for a class. This can be beneficial in some situations, even though you could achieve the same functionality with an empty constructor definition.

Benefits of "= default"

The "= default" syntax offers several advantages over an empty constructor definition:

• 明确意图: By explicitly specifying that a default constructor should be generated, you make your code easier to read and understand.
• Ensures Aggregate and Trivial Properties: If you want your class to be an aggregate or trivial type, you must use "= default" to ensure that no user-provided initializations or compound statements are present.
• Consistency and Uniformity: The "= default" syntax can be used consistently with copy/move constructors and destructors, making your code more uniform and easier to read.

Clarifying the Differences

While both "= default" constructors and empty constructors will behave similarly in terms of functionality, they have subtle differences:

• constexpr: An explicitly defaulted constructor is constexpr if the implicit constructor would have been.
• Exception Specification: An explicitly defaulted constructor will have the same exception specification as the implicit constructor.
• Aggregate and Trivial Types: An explicitly defaulted constructor preserves aggregate and trivial class properties, while an empty constructor does not.

Conclusion

The "= default" syntax in C 11 provides an explicit way to request the generation of default special member functions, including default constructors. It can help to improve code readability, ensure specific class properties, and promote consistency throughout your codebase.

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