【面经笔记】内存泄漏检测

参考：
http://www.cnblogs.com/juncheng/archive/2009/11/12/1602165.html

• new/new[]表达式会首先调用operator new/new[]操作运算符函数开辟内存，再调用构造函数构造对象

• 而为了给操作运算符函数传递额外的参数：文件名与行号，需要使用定位new表达式（C++primer P729）
  new(void ) type -> operator new(size_t,void )

  new(char*,int) type -> operator new(size_t,char* ,int )

定位new表达式一般用于placemen new：
http://www.cppblog.com/kongque/archive/2010/02/20/108093.html

• 重载operator new/delete/new[]/delete[] 四个运算操作符函数

• 使用map保存指针及分配它的代码所在位置信息，new中插入，delete中删除

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#include <iostream>#include <vector>#include <numeric>#include<algorithm>#include <stack>#include <string>#include <map>using namespace std;class A{public:    int a = 1;};#define debug_#ifdef debug_map<void*, pair<char*, int>> my_map;void * __cdecl operator new(unsigned int size, const char *file, int line){    void* p = malloc(size);    pair<char*, int> tmp_2(const_cast<char *>(file), line);    pair<void*, pair<char*, int>> tmp(p, tmp_2);    my_map.insert(tmp);    cout << "new" << endl;    return p;};void * __cdecl operator new[](unsigned int size, const char *file, int line){    void* p = malloc(size);    pair<char*, int> tmp_2(const_cast<char *>(file), line);    pair<void*, pair<char*, int>> tmp(p, tmp_2);    my_map.insert(tmp);    cout << "new[]" << endl;    return p;};void __cdecl operator delete(void *p){    if(my_map.erase(p))        cout << "delete" << endl;    free(p);};void __cdecl operator delete[](void *p){    if(my_map.erase(p))        cout << "delete []" << endl;    free(p);};#define new new(__FILE__,__LINE__)#endifint main(){    auto tmp_1 = new A;    auto tmp_2 = new A[5];    //delete tmp_1;    //delete[] tmp_2;    return 0;}