Does C 's Default Constructor Initialize Built-in Type Members?

Default Constructor Behavior with Built-in Types

Question:

Do default constructors, automatically generated by the compiler, initialize built-in types in C ?

Answer:

No, the default constructor (created by the compiler for classes without user-defined constructors) does not initialize members of built-in types.

However, it's important to note that there are other mechanisms for initializing class instances that do not involve the default constructor:

• Value-initialization: The syntax C() (when no user-declared constructor is available) performs value-initialization, which zero-initializes built-in types.
• Aggregate initialization: The syntax C {} or C{}; initializes all members of a class without invoking any constructors.

Example:

Consider the following class:

class C {
public:
  int x;
};

The compiler-provided default constructor for C will not initialize C::x.

C c; // Compiler-provided default constructor is used
// c.x contains garbage

In contrast, using value-initialization or aggregate initialization will zero-initialize C::x:

C c = C(); // Uses value-initialization instead of default constructor
            // c.x == 0

C d{}; // Aggregate initialization
       // d.x == 0

The above is the detailed content of Does C 's Default Constructor Initialize Built-in Type Members?. For more information, please follow other related articles on the PHP Chinese website!