When is User-Defined Copy Constructor Necessary in C ?

User-Defined Copy Constructor in C

In C , the compiler typically generates a default copy constructor for classes, which performs member-wise copying. However, in certain scenarios, a user-defined copy constructor is necessary.

When is a user-defined copy constructor needed?

A user-defined copy constructor is required when the default copy constructor's member-wise copying behavior is insufficient. Consider the following example:

<code class="cpp">class Class {
public:
    Class(const char* str);
    ~Class();
private:
    char* stored;
};

Class::Class(const char* str) {
    stored = new char[srtlen(str) + 1];
    strcpy(stored, str);
}

Class::~Class() {
    delete[] stored;
}</code>

In this example, the default copy constructor would simply copy the pointer to the stored member, rather than duplicating the underlying buffer. This can lead to undefined behavior if one copy is destroyed before the other.

User-Defined Copy Constructor

To address this, you can define a user-defined copy constructor that performs deep copying:

<code class="cpp">Class::Class(const Class& another) {
    stored = new char[strlen(another.stored) + 1];
    strcpy(stored, another.stored);
}</code>

This copy constructor allocates new memory and copies the contents of the stored member, ensuring that both copies have their own independent buffers.

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