Chapter 9: Problem 8

What happens when a program uses the new operator to allocate a block of memory, but the amount of requested memory isn't available? How do programs written with older compilers handle this?

Short Answer

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Answer: In C++ programs using a modern compiler, the 'new' operator throws an exception of type std::bad_alloc if the requested memory allocation fails. To handle this exception, a try-catch block can be used to catch the exception and take the appropriate action. In older compilers that do not support exception handling, the 'new' operator returns a nullptr (NULL in C++) when memory allocation fails, allowing the programmer to handle the situation appropriately.

Step by step solution

Understanding the 'new' operator for memory allocation

The 'new' operator is used in C++ for allocating memory dynamically during the runtime of a program. When the new operator is used, it requests a certain amount of memory from the system's memory manager. If the requested memory is available, the memory manager allocates the memory and returns the address of the first block of memory. If the memory isn't available, an exception is thrown.

Handling memory allocation failure with the 'new' operator

When a program uses the new operator to allocate memory and the requested memory isn't available, an exception of type std::bad_alloc is thrown. To handle this exception, the programmer can use a try-catch block to catch the exception and take appropriate action. Here is an example of how to handle std::bad_alloc exception: ```cpp #include #include int main() { try { int* myArray = new int[100000000000]; // Requesting a large amount of memory allocation } catch (std::bad_alloc& ex) { std::cerr << "Memory allocation failed: " << ex.what() << std::endl; } return 0; } ``` In the example above, if the memory allocation fails, it will catch the std::bad_alloc exception and print an error message.

Memory allocation handling with older compilers

In older compilers, specifically those that do not support exception handling, the 'new' operator returns a nullptr (NULL in C++) when memory allocation fails instead of throwing a std::bad_alloc exception. Here is how to handle memory allocation failure in older compilers: ```cpp #include int main() { int* myArray = new(std::nothrow) int[100000000000]; // Requesting a large amount of memory allocation if (myArray == nullptr) { std::cerr << "Memory allocation failed!" << std::endl; } return 0; } ``` In the example above, if the memory allocation fails, the value of myArray will be `nullptr`, allowing the programmer to handle the situation appropriately.

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What happens when a program uses the new operator to allocate a block of memory, but the amount of requested memory isn't available? How do programs written with older compilers handle this?

Short Answer

Step by step solution

Understanding the 'new' operator for memory allocation

Handling memory allocation failure with the 'new' operator

Memory allocation handling with older compilers

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