Question

Write a program that generates and handles a memory-exhaustion exception. Your program should loop on a request to create dynamic memory through operator new.

Short answer

Write a loop to allocate large memory blocks using `new` and handle `std::bad_alloc` exceptions.

Step-by-step solution

Set Up the Environment

Begin by including the necessary header files. In C++, you will need `#include ` to throw and catch exceptions related to memory allocation. Additionally, use `#include ` for input and output operations.

Define the Main Function

In your main function, you need to write a loop that continuously requests large amounts of memory using the `new` operator. For this task, a while loop will work best. Ensure your loop has a termination condition or another method to handle the exception.

Allocate Memory Inside a Try Block

Inside the loop, use a try block to handle the potential exception. In each iteration, attempt to allocate a large array of integers using the `new` operator. The size can be very large, such as `new int[1000000000]`. This is likely to fail due to the excessive size.

Handle the Exception

After the try block, use a catch block to handle the `std::bad_alloc` exception. This specific exception is thrown when the `new` operator fails to allocate the requested memory. In the catch block, print an error message indicating that memory allocation has failed.

Clean Up and Return from the Function

Once an exception is caught, exit the loop, clean up any dynamically allocated memory, if any, and safely terminate the program. Finally, return 0 from the main function to indicate successful completion even though an exception occurred.

Key concepts

Dynamic Memory Allocation

Dynamic memory allocation in C++ is a method that allows you to allocate memory during the runtime of a program. This can be useful when you do not know the amount of memory you need before the program runs. Unlike static memory allocation, which is fixed at compile time, dynamic memory can flexibly grow and shrink as needed.
To allocate dynamic memory in C++, you'll typically use the `new` operator. It returns a pointer to the beginning of a block of memory of the requested size. For example, `new int[10]` attempts to allocate memory for an array of 10 integers.

• Advantages: Provides flexibility to programs that require variable amounts of memory.
• Disadvantages: Improper use can lead to memory leaks if allocated memory is not properly deallocated.

Keep in mind the importance of using `delete` to free up the memory once it's no longer needed. This careful practice is crucial in avoiding memory leaks.

std::bad_alloc Exception

The `std::bad_alloc` exception is part of the exception handling mechanism in C++. It's specifically thrown by the `new` operator when it fails to allocate the requested memory. This typically happens when the system does not have enough available memory to fulfill the request.
The `std::bad_alloc` exception belongs to the standard library and inherits from the `std::exception` class. To handle a `std::bad_alloc` exception, you should surround your memory allocation attempt with a try block, followed by a catch block that specifies `std::bad_alloc` as its exception type.

• Why it occurs: When memory request exceeds available physical memory.
• Handling: Use catch blocks to manage failures gracefully rather than crashing the application.

Implementing this exception handling is critical, especially in software where reliability and stability are required even under heavy memory usage.

Try and Catch Blocks

Try and catch blocks are the backbone of exception handling in C++. They allow you to test segments of code and handle exceptions efficiently. This technique helps to prevent programs from crashing abruptly upon encountering an error.
A try block surrounds the code that might throw an exception. Immediately following the try block is one or more catch blocks, which specify exception types they are capable of handling.

• Try Block: Contains code that might lead to an exception.
• Catch Block: Executes when a specific exception occurs in the try block.

Consider an example of allocating memory using `new`. You would place this inside the try block. If the allocation fails, it throws a `std::bad_alloc` exception, which is then caught by the catch block, allowing for cleanup or recovery measures.

Memory Management in C++

Memory management in C++ involves several techniques and considerations to ensure that the program runs efficiently and without running out of memory. A key aspect is the allocation and deallocation of memory using tools such as `new` and `delete`.
Developers need to be mindful of where and how memory is managed in their applications to maintain performance and prevent leaks. A memory leak happens if dynamically allocated memory is not freed. Over time, this can drastically reduce available memory.

• Best Practices: Always ensure every `new` has a corresponding `delete`.
• Tools: Utilize smart pointers like `std::unique_ptr` or `std::shared_ptr` to automate memory management.

By effectively managing memory, developers can create robust applications that utilize system resources responsibly.