What Happens to Class Members When Initialization is Omitted?

Class Member Initialization and Implicit Defaults

When dealing with class member initialization, it's essential to understand the implicit processes that occur when explicit initialization is neglected. This knowledge is crucial for ensuring bug-free programs.

For objects, the default constructor will be invoked. Consider std::string, where the default constructor initializes it as an empty string. However, if the class lacks a default constructor, explicit initialization is mandatory.

Primitive types, including pointers, remain uninitialized and retain previous memory contents, which may be arbitrary data.

References, on the other hand, must always be initialized; therefore, attempting to leave them uninitialized will result in compilation errors.

Examining your provided class structure:

class Example {
    int *ptr;
    string name;
    string *pname;
    string &rname;
    const string &crname;
    int age;
};

If no explicit initialization is performed, the member variables will assume the following states:

ptr: Contains junk (arbitrary memory value)
name: Initialized as an empty string ("")
pname: Contains junk (arbitrary memory value)
rname: Compilation error (required initialization)
crname: Compilation error (required initialization)
age: Contains junk (arbitrary memory value)

Understanding these implicit initialization mechanisms is essential for writing robust and error-free programs.

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