stdsetnewhandler

The std::set_new_handler is a function in the C++ Standard Library that allows programmers to specify a custom handler function to be called when memory allocation via new fails. It is part of the <new> header and plays a crucial role in managing dynamic memory allocation and error handling.

When a C++ program requests memory using new, the system attempts to allocate the required memory. If the allocation fails—due to insufficient memory or other system constraints—the std::set_new_handler allows the programmer to define a function that handles this failure situation. The custom handler can attempt to free resources, log errors, or perform alternative actions before deciding to terminate the program or take other measures.

The std::set_new_handler function takes a pointer to a function with no parameters and a void return type. Calling this function sets the specified handler as the new global handler for subsequent failed memory allocations. If multiple calls are made, the previous handler is replaced.

Standard behavior when a memory allocation fails and no handler is set results in a std::bad_alloc exception being thrown from new. However, with std::set_new_handler, the custom handler can attempt to recover or gracefully shut down the program, potentially preventing exceptions or aborts.

The function can be reset by calling std::set_new_handler(nullptr), restoring the default behavior of throwing std::bad_alloc. Proper use of std::set_new_handler can improve the resilience and robustness of C++ applications in memory-constrained environments.

References:

- ISO/IEC 14882:2020 (C++20 Standard)

- "C++ Programming Language" by Bjarne Stroustrup