C++ “free()” and the “delete” Operator

When it comes to managing memory in C++, there are two commonly used methods: the “free()” function and the “delete” operator. Both serve the purpose of deallocating dynamically allocated memory, but they have some key differences that are important to understand.

The “free()” Function

The “free()” function is a part of the C programming language and is also available in C++. It is used to deallocate memory that was allocated using the “malloc()” or “calloc()” functions. Here’s an example:

#include <cstdlib>
#include <iostream>

int main() {
    int* ptr = (int*)malloc(sizeof(int));
    *ptr = 5;
    
    std::cout << *ptr << std::endl; // Output: 5
    
    free(ptr);
    
    return 0;
}

In the above example, we allocate memory for an integer using the “malloc()” function and assign a value of 5 to it. After we are done using the memory, we deallocate it using the “free()” function.

It’s important to note that the “free()” function does not call the destructor of any objects stored in the memory being deallocated. It simply releases the memory back to the system. Therefore, it should not be used to deallocate memory for objects that have constructors and destructors.

The “delete” Operator

The “delete” operator is a part of C++ and is used to deallocate memory that was allocated using the “new” operator. Here’s an example:

#include <iostream>

int main() {
    int* ptr = new int;
    *ptr = 5;
    
    std::cout << *ptr << std::endl; // Output: 5
    
    delete ptr;
    
    return 0;
}

In this example, we allocate memory for an integer using the “new” operator and assign a value of 5 to it. After we are done using the memory, we deallocate it using the “delete” operator.

Unlike the “free()” function, the “delete” operator calls the destructor of any objects stored in the memory being deallocated. This makes it suitable for deallocating memory for objects that have constructors and destructors.

Choosing Between “free()” and “delete”

When working with C++, it is generally recommended to use the “new” operator and the “delete” operator for memory management. This is because the “new” operator is more aligned with the object-oriented nature of C++ and ensures that the destructor of objects is called when memory is deallocated.

The “free()” function is typically used when working with legacy C code or when interoperability with C code is required. However, it should be used with caution, especially when dealing with objects that have constructors and destructors.

Here’s a summary of the key differences between the “free()” function and the “delete” operator:

1. The “free()” function is used to deallocate memory allocated with “malloc()” or “calloc()”, while the “delete” operator is used to deallocate memory allocated with the “new” operator.
2. The “free()” function does not call the destructor of any objects stored in the memory being deallocated, while the “delete” operator does.
3. The “delete” operator is more aligned with the object-oriented nature of C++ and is recommended for memory management in C++ code.

In conclusion, understanding the differences between the “free()” function and the “delete” operator is crucial for effective memory management in C++. By choosing the appropriate method based on the situation, you can ensure the proper deallocation of memory and prevent memory leaks in your code.