1.set_new_handler机制的运行原理：
<span style="font-size:18px;">#include <iostream> using namespace std; void out_of_memory() { cout<<"out of memory!"<<endl; } int main() { set_new_handler(out_of_memory); int *p = new int[536870911]; return 0; }</span> 当new发生错误时，调用set_new_handler(）的出错处理函数。
2.new的实现以及模拟set_new_handler机制： new的内部行为分为三步： 1.内存开辟成功； 2.开辟失败，设置有出错函数，则调用出错处理函数； 3.开辟失败，没有设置出错处理函数，则抛出异常。
<span style="font-size:18px;">#include <iostream> using namespace std; typedef void (*new_handler)(); class x { public: static new_handler set_new_handler(new_handler p); static void *operator new[](size_t size); private: static new_handler currenthandler; int data; }; new_handler x::currenthandler = 0; new_handler x::set_new_handler(new_handler p) { new_handler oldhandler = currenthandler; currenthandler = p; return oldhandler; } void* x::operator new[](size_t size) //new的内部行为 { if(size == 0) { size = 1; } void *result; while(1) { result = malloc(size); //1.开辟成功 if(result != NULL) return result; new_handler globalhandler = set_new_hanler(0); //设置出错处理函数 set_new_handler(globalhandler); if(globalhandler) (*globalhandler)(); //2.调用出错处理函数 else throw std::bad_alloc(); //3.抛出异常 } } void out_of_memory() { cout<<"out of memory!"<<endl; exit(1); } int main() { x::set_new_handler(out_of_memory); try { x *px = new x[536870912]; } catch(bad_alloc &e) { cout<<e.what()<<endl; } return 0; }</span>