Question

Consider the following C++ code: int *p; p = new int[10]; for (int j = 0; j < 10; j++) p[i] = 2 * j - 2; Write the C++ statement that deallocates the memory space occupied by the array to which p points.

Short answer

Use `delete[] p;` to deallocate the array memory.

Step-by-step solution

Understanding Dynamic Memory Allocation in C++

In the given C++ code snippet, a pointer `p` is declared and is used to allocate memory for an array of 10 integers using the `new` operator. The memory for this array, pointed to by `p`, needs to be explicitly deallocated to prevent memory leaks.

Identifying Deallocation Requirement

In C++, when you use `new` to allocate memory for an array, you must use the corresponding `delete[]` operator to deallocate this memory when you are done using it. This ensures that the operating system can reclaim the memory and it prevents memory leaks.

Writing the C++ Statement for Deallocation

To deallocate the memory space occupied by the array that `p` points to, you need to use the `delete[]` operator followed by the pointer variable. The correct statement is: ```c++ delete[] p; ```

Key concepts

Memory Management

In C++, memory management is a crucial concept that involves controlling and coordinating a computer's memory. This includes allocating memory space for variables and data structures, as well as deallocating it when it is no longer needed.

When you write a program, memory can be allocated in a few different ways. You can allocate memory statically, dynamically, or automatically. Static memory allocation happens at compile time, while dynamic memory allocation occurs at runtime.

Dynamic memory allocation is very flexible, allowing programs to request and use memory as needed. This is done using the `new` operator in C++. With `new`, you can allocate memory for a single variable or an entire array, just as in the exercise example.

After you're done using dynamically allocated memory, you must free it using the `delete` operator. For arrays, it's important to use `delete[]` to properly release the memory and avoid unpredictable behavior.

Pointers in C++

Pointers are variables that store memory addresses. They are powerful tools in C++ because they allow you to directly access and manipulate memory addresses.

When you declare a pointer, you can assign it the address of another variable. For example, in the exercise, `int *p` declares a pointer that can hold the address of an `int` variable or array.

Using pointers, you can pass variables to functions efficiently, create dynamic data structures like linked lists, and have more control over memory usage. They are fundamental when working with dynamic memory allocation, as they store the memory address of the allocated space.

You'll often use pointers with the `new` and `delete` operators to manage memory efficiently. Mastering pointers can greatly enhance your understanding of C++ and your ability to write efficient and powerful code.

Preventing Memory Leaks

A memory leak occurs when a program does not release memory that is no longer needed, leading to wasted resources and potential program errors. In dynamic memory allocation, an operating system allocates memory from the heap.

If you forget to deallocate memory using `delete` or `delete[]`, your program continues to hold onto this memory even if it's no longer needed. This can slowly consume system memory, leading to slower performance or program crashes.

To prevent memory leaks, follow these best practices:

• Always pair `new` with `delete`, and `new[]` with `delete[]`.
• Use smart pointers from the C++ Standard Library, such as `std::unique_ptr` and `std::shared_ptr`, which automatically manage memory for you.
• Regularly review your code and check for any allocations that do not have corresponding deallocations.

By following these strategies, you can write robust C++ programs that manage resources efficiently and prevent memory leaks.