规则：如果一个带额外参数的operator new没有“带相同参数”的对应版operator delete，那么就当new的内存分配动作取消并恢复原样时就没有任何operator delete被调用，于是产生内存泄露。
例程：
1 class Wigget{ 2 public: 3 int a; 4 static void* operator new(std::size_t size, std::ostream& logstream) throw(std::bad_alloc){ 5 std::cout << "in myself new func !!!" << std::endl; 6 return ::operator new(size);; 7 } 8 static void operator delete(void* pM) throw(){ 9 ::operator delete(pM); 10 std::cout << "in delete func !!!" << std::endl; 11 } 12 static void operator delete(void* pM, std::ostream& logstream) throw(){ 13 ::operator delete(pM); 14 std::cout << "in myself delete func !!!" << std::endl; 15 } 16 }; 17 18 int _tmain(int argc, _TCHAR* argv[]){ 19 Wigget *p1 = new(std::cerr) Wigget(); 20 delete p1; 21 return 0; 22 }
运行结果：
由以上代码可以得出以下结论：
全局作用域下提供的new:
1 void* operator new(std::size_t) throw(std::bad_alloc); //正常形式的new 2 void* operator new(std::size_t, void *) throw(); //placement形式 new 3 void* operator new(std::size_t, const std::nothrow_t&) throw(); //失败返回NULL的new
写了placement new也要写placement delete
原文：https://www.cnblogs.com/xiongxinxzy/p/13092432.html