typedef void (*new_handler)();
Type of new handler function
This is a typedef of a
void function with no parameters, used as the argument and return type in function set_new_handler.
A new-handler function is a function that is called by the standard definition of functions operator new and operator new when they fail to allocate memory.
For more info, see the reference for set_new_handler, which is the function used to set a function of this type as the active new-handler.