


Why Is Aggregate Initialization No Longer Allowed for Structs with Explicitly Defaulted or Deleted Constructors in C 20?
Nov 03, 2024 am 08:29 AMAggregate Initialization in C 20
In C 20, aggregate initialization for structs that have explicitly defaulted or deleted constructors has undergone a significant change. This alteration affects code that was previously valid but now generates errors.
Pre-C 20 Compatibility
Before C 20, aggregate initialization was allowed for structs that possessed user-provided, inherited, or explicitly defaulted or deleted constructors. This permitted the bypass of constructors during initialization.
C 20 Standards
However, the C 20 standard has revised this behavior. Aggregate initialization is now permitted only for structs that lack user-declared or inherited constructors. Explicitly defaulted or deleted constructors are no longer allowed. This change was implemented to address ambiguity and confusion in initialization semantics.
Rationale for the Change
The rationale behind this change in C standards is rooted in the desire to enhance the safety, uniformity, and clarity ofinitialization. The previous behavior could lead to unexpected and erroneous code, as illustrated by:
struct X { int i{4}; X() = default; }; int main() { X x1(3); // ill-formed - no matching c’tor X x2{3}; // compiles! }
In this example, the default constructor of X cannot be used for initialization due to the declaration of the member variable i with an initial value of 4. However, aggregate initialization is erroneously permitted, leading to ambiguous and potentially incorrect behavior.
Implications for Code
This change necessitates code modifications for cases where aggregate initialization was previously used with explicitly defaulted or deleted constructors. It prompts developers to reconsider the practice of explicitly defaulting constructors for aggregate data types.
In conclusion, the C 20 standard change regarding aggregate initialization aims to improve the reliability and consistency of initialization idioms, justifying the potential backwards-incompatibility it introduces.
The above is the detailed content of Why Is Aggregate Initialization No Longer Allowed for Structs with Explicitly Defaulted or Deleted Constructors in C 20?. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undress AI Tool
Undress images for free

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

Yes, function overloading is a polymorphic form in C, specifically compile-time polymorphism. 1. Function overload allows multiple functions with the same name but different parameter lists. 2. The compiler decides which function to call at compile time based on the provided parameters. 3. Unlike runtime polymorphism, function overloading has no extra overhead at runtime, and is simple to implement but less flexible.

C has two main polymorphic types: compile-time polymorphism and run-time polymorphism. 1. Compilation-time polymorphism is implemented through function overloading and templates, providing high efficiency but may lead to code bloating. 2. Runtime polymorphism is implemented through virtual functions and inheritance, providing flexibility but performance overhead.

Yes, polymorphisms in C are very useful. 1) It provides flexibility to allow easy addition of new types; 2) promotes code reuse and reduces duplication; 3) simplifies maintenance, making the code easier to expand and adapt to changes. Despite performance and memory management challenges, its advantages are particularly significant in complex systems.

C destructorscanleadtoseveralcommonerrors.Toavoidthem:1)Preventdoubledeletionbysettingpointerstonullptrorusingsmartpointers.2)Handleexceptionsindestructorsbycatchingandloggingthem.3)Usevirtualdestructorsinbaseclassesforproperpolymorphicdestruction.4

Polymorphisms in C are divided into runtime polymorphisms and compile-time polymorphisms. 1. Runtime polymorphism is implemented through virtual functions, allowing the correct method to be called dynamically at runtime. 2. Compilation-time polymorphism is implemented through function overloading and templates, providing higher performance and flexibility.

People who study Python transfer to C The most direct confusion is: Why can't you write like Python? Because C, although the syntax is more complex, provides underlying control capabilities and performance advantages. 1. In terms of syntax structure, C uses curly braces {} instead of indentation to organize code blocks, and variable types must be explicitly declared; 2. In terms of type system and memory management, C does not have an automatic garbage collection mechanism, and needs to manually manage memory and pay attention to releasing resources. RAII technology can assist resource management; 3. In functions and class definitions, C needs to explicitly access modifiers, constructors and destructors, and supports advanced functions such as operator overloading; 4. In terms of standard libraries, STL provides powerful containers and algorithms, but needs to adapt to generic programming ideas; 5

C polymorphismincludescompile-time,runtime,andtemplatepolymorphism.1)Compile-timepolymorphismusesfunctionandoperatoroverloadingforefficiency.2)Runtimepolymorphismemploysvirtualfunctionsforflexibility.3)Templatepolymorphismenablesgenericprogrammingfo

C polymorphismisuniqueduetoitscombinationofcompile-timeandruntimepolymorphism,allowingforbothefficiencyandflexibility.Toharnessitspowerstylishly:1)Usesmartpointerslikestd::unique_ptrformemorymanagement,2)Ensurebaseclasseshavevirtualdestructors,3)Emp
