内存分配失败的处理

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看到effective c++中内存分配的处理，编写代码便于以后的理解：

1. 基本版：

#include <new.h>#include <iostream>using namespace std;int PrintError(size_t size){cout<<"memory failed in allocation/t"<<size<<endl;return 0;//return 1; if executes here, then this function will be called //until the memory allocation success.}void main(){_set_new_handler(PrintError);int *pInt = new int[999999999999999];}

msdn上这么解释：

Call the C++ _set_new_handler function to specify an exception-handling function that is to gain control if the new operator fails to allocate memory. If new fails, the run-time system automatically calls the exception-handling function that was passed as an argument to _set_new_handler. _PNH, defined in NEW.H, is a pointer to a function that returns type int and takes an argument of type size_t. Use size_t to specify the amount of space to be allocated.

_set_new_handler is essentially a garbage-collection scheme. The run-time system retries allocation each time your function returns a nonzero value and fails if your function returns 0.

2. effective c++上提供的一条有效的建议是提供一个类作为基类，这样子类

等出现内存分配失败时，均可以用到，也可以写为模板类，代码如下：

NewClass.h代码：// NewClass.h: interface for the CNewClass class.////////////////////////////////////////////////////////////////////////#if !defined(AFX_NEWCLASS_H__90CDE415_B093_4E3C_B1B9_DD3DA750E7A9__INCLUDED_)#define AFX_NEWCLASS_H__90CDE415_B093_4E3C_B1B9_DD3DA750E7A9__INCLUDED_#if _MSC_VER > 1000#pragma once#endif // _MSC_VER > 1000#include <new.h>class CNewClass {public:CNewClass();virtual ~CNewClass();public:static _PNH set_new_handler(_PNH p);static void * operator new(size_t size);private:static _PNH currenthandler;int m_int[9999999999];};#endif // !defined(AFX_NEWCLASS_H__90CDE415_B093_4E3C_B1B9_DD3DA750E7A9__INCLUDED_)NewClass.cpp文件代码：// NewClass.cpp: implementation of the CNewClass class.////////////////////////////////////////////////////////////////////////#include "NewClass.h"#include <new>//////////////////////////////////////////////////////////////////////// Construction/Destruction//////////////////////////////////////////////////////////////////////CNewClass::CNewClass(){}CNewClass::~CNewClass(){}_PNH CNewClass::set_new_handler(_PNH p){_PNH oldhandler = currenthandler;currenthandler = p;return oldhandler;}void * CNewClass::operator new(size_t size){_PNH globalhandler = _set_new_handler(currenthandler);void *memory;try { // 尝试分配内存memory = ::operator new(size);}catch (std::bad_alloc&) { // 恢复旧的new_handler_set_new_handler(globalhandler); throw;// 抛出异常}_set_new_handler(globalhandler);// 恢复旧的new_handlerreturn memory;}_PNH CNewClass::currenthandler;在main中使用代码：#include "NewClass.h"#include <stdlib.h>#include <iostream>using namespace std;int NonMemory(size_t size){cout<<size<<"has been allocated!"<<endl;return 0;}void main(){CNewClass *pnew;CNewClass::set_new_handler(NonMemory);pnew = new CNewClass;pnew = new CNewClass;}

为了让内存尽快耗完，我在class内部定义一个大block的内存块，这样就能在

main中定义到第二个变量时变出现了内存分配失败的情形，其实在NonMemory这样的函数中，

应该尽量做到垃圾内存回收，并且返回1，这样的话，会让分配失败后，继续调用分配内存，这样才是