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++, when you use the `new` keyword to allocate memory, it reserves space on the heap. Here, `p = new int[10];` dynamically allocates an array of 10 integers. This memory remains allocated until you explicitly deallocate it.

Identifying the Deallocation Requirement

Dynamically allocated memory should be freed using the `delete` keyword. If you don't deallocate memory, it leads to memory leaks, where unneeded memory remains occupied.

Choosing the Correct Deallocation Syntax

Since `p` points to a dynamically allocated array (of type `int`), the correct syntax to deallocate is `delete[] p;`. This ensures that the entire array, not just a single element, is deallocated.

Writing the Deallocation Statement

The statement `delete[] p;` should be used right after you're done using the allocated memory. This statement deallocates the memory space occupied by the array that `p` points to.

Key concepts

Dynamic Memory Allocation

Dynamic memory allocation is a key feature in C++ that allows for the allocation of memory during runtime. This process gives programmers the flexibility to handle data sizes that may not be known during the compilation of the program. By using the `new` keyword, you can request memory from the heap, a special memory region reserved for dynamically allocated objects.

When you declare `int *p;` and later use `p = new int[10];`, you are telling the program to allocate an array of 10 integers on the heap. This memory remains unavailable to other variables until explicitly deallocated.

This technique not only optimizes memory usage but also accommodates varying data needs, enhancing program robustness. However, it comes with the responsibility of manual management, which if neglected, can lead to memory issues.

Memory Leak Prevention

Memory leaks occur when dynamically allocated memory is not reclaimed after use. This happens when pointers lose reference to the allocated memory without deallocating it, leading to wasted resources and potentially slowing down your program.

To prevent memory leaks, follow these strategies:

• Ensure every `new` operation has a corresponding `delete` operation.
• Implement checks to verify that memory is correctly deallocated.
• Use smart pointers, introduced in C++11, which automatically manage memory deallocation and reduce the risk of leaks.

By maintaining good memory management practices, you will conserve resources and avoid potential pitfalls of unmanaged memory.

Delete Operator

The `delete` operator is essential in C++ for managing dynamic memory. It releases memory allocated using `new`, making it available for future allocations. Proper use of `delete` prevents memory leaks and other common memory-related errors.

For single objects allocated with `new`, use `delete p;`. For an array, like in the exercise, it is crucial to use `delete[] p;`. This distinction ensures correct memory operation because `delete[]` understands the specific deallocation requirements of arrays.

Usage of the `delete` operator is straightforward:

• For single variable allocation: `delete varName;`
• For arrays: `delete[] arrayName;`

Understanding when and how to use the `delete` operator effectively will significantly enhance your control over memory management.

Array Deallocation

In C++, arrays are a common structure for handling collections of data. When arrays are dynamically allocated using `new`, it's important to deallocate them carefully to prevent memory leaks and free up resources.

The syntax `delete[] p;` is used to deallocate memory that was previously allocated for an array. The brackets `[]` indicate to the compiler that all elements in the array should be deallocated, not just a single element. This prevents partial deallocation, which could lead to undefined behavior.

Key steps for array deallocation include:

• Use `delete[]` specifically for arrays to ensure complete deallocation.
• Place the `delete[]` statement immediately after you're done using the array to avoid lingering occupied memory.
• Regularly checking for pointer nullity before deletion helps avoid runtime errors.

Proper array deallocation is vital for writing efficient and safe C++ programs.