What can “new_handler” be used for in C++ besides garbage collection?

Question

C++ programs can define and set a new_handler() that should be called from memory allocation functions like operator new() if it\'s impossible to a

Answer 1

On most of the servers I've worked on, the new_handler freed a pre-allocated block (so future new's wouldn't fail) before logging a message (the logger used dynamic memory) and aborting. This ensured that the out of memory error was correctly logged (instead of the process just "disappearing", with an error message to cerr, which was connected to /dev/null).

In applications such as editors, etc., it may be possible to spill parts of some buffers to disk, then continue; if the new_handler returns, operator new is supposed to retry the allocation, and if the new_handler has freed up enough memory, the allocation may succeed (and if it doesn't, the new_handler will be called again, to maybe free up even more).