Is Aggregate Initialization Still Possible for Structs with Explicitly Defaulted or Deleted Constructors in C 20?

Impact of Explicit Constructor Defaulting and Deletion on Aggregate Initialization in C 20

Since the introduction of C 20, there has been a notable change in the behavior of aggregate initialization when constructors are explicitly defaulted or deleted. In this discussion, we will investigate the reasons behind this alteration and its implications for developers.

The Change in C 20

Prior to C 20, aggregate initialization was permitted for structs with user-provided constructors, as long as those constructors were not explicitly defaulted or deleted. However, in C 20, this exception has been removed, meaning that structs with explicitly defaulted or deleted constructors can no longer be initialized using aggregates.

Reasoning Behind the Change

The change in C 20 was introduced to enhance the safety and consistency of initialization semantics. Specifically, the issue revolves around the potential confusion caused by the coexistence of aggregate initialization and constructors within the same struct. Consider the following example:

<code class="cpp">struct Foo
{
    int bar;
    Foo() = default;
};

int main()
{
    Foo f { 0 }; // Error in C++20
}</code>

In this example, the struct Foo has an explicitly defaulted constructor. Prior to C 20, this code would have been valid, with aggregate initialization bypassing the default constructor. However, in C 20, this behavior is disallowed to prevent the user from unintentionally bypassing crucial initialization logic.

Consequences for Developers

The change in C 20 has removed a previously available option for initializing structs with constructors. As a result, developers who relied on explicitly defaulted or deleted constructors for aggregate initialization will need to re-evaluate their approach.

Conclusion

The removal of aggregate initialization for structs with explicitly defaulted or deleted constructors in C 20 aims to improve initialization safety and consistency. While this may introduce some inconvenience for developers who previously used this technique, the overall benefits of enhanced clarity and reliability outweigh the drawbacks. Developers are encouraged to adapt their code to align with this change and consider alternative initialization methods if necessary.

The above is the detailed content of Is Aggregate Initialization Still Possible for Structs with Explicitly Defaulted or Deleted Constructors in C 20?. For more information, please follow other related articles on the PHP Chinese website!