C++内存泄露的检测（三）

一 简单的对内存的分配和释放跟踪，并将结果输出到console，它也是一般C++内存泄露的检测原理，来自C++编程思想：
（比较简单，大家都可以看的明白的哦）实现如下：

MemCheck.h

//: C02:MemCheck.h
#ifndef MEMCHECK_H
#define MEMCHECK_H
#include <cstddef>  // for size_t

// Hijack the new operator (both scalar and array versions)
void* operator new(std::size_t, const char*, long);
void* operator new[](std::size_t, const char*, long);
#define new new (__FILE__, __LINE__)

extern bool traceFlag;
#define TRACE_ON() traceFlag = true
#define TRACE_OFF() traceFlag = false

extern bool activeFlag;
#define MEM_ON() activeFlag = true
#define MEM_OFF() activeFlag = false

#endif

 MemCheck.cpp

//: C02:MemCheck.cpp {O}
#include <cstdio>
#include <cstdlib>
#include <cassert>
using namespace std;
#undef new

// Global flags set by macros in MemCheck.h
bool traceFlag = true;
bool activeFlag = false;

namespace {

// Memory map entry type
struct Info {
  void* ptr;
  const char* file;
  long line;
};

// Memory map data
const size_t MAXPTRS = 10000u;
Info memMap[MAXPTRS];
size_t nptrs = 0;

// Searches the map for an address
int findPtr(void* p) 
{
  for (int i = 0; i < nptrs; ++i)
    if (memMap[i].ptr == p)
      return i;
  return -1;
}

void delPtr(void* p)
{
  int pos = findPtr(p);
  assert(p >= 0);
  // Remove pointer from map
  for (size_t i = pos; i < nptrs-1; ++i)
    memMap[i] = memMap[i+1];
  --nptrs;
}

// Dummy type for static destructor
struct Sentinel 
{
  ~Sentinel()
  {
    if (nptrs > 0) 
    {
      printf("Leaked memory at:\n");
      for (size_t i = 0; i < nptrs; ++i)
        printf("\t%p (file: %s, line %ld)\n",
          memMap[i].ptr, memMap[i].file, memMap[i].line);
    }
    else
      printf("No user memory leaks!\n");
  }
};

// Static dummy object
Sentinel s;

} // End anonymous namespace

// Overload scalar new
void* operator new(size_t siz, const char* file,
  long line) {
  void* p = malloc(siz);
  if (activeFlag)
  {
    if (nptrs == MAXPTRS)
    {
      printf("memory map too small (increase MAXPTRS)\n");
      exit(1);
    }
    memMap[nptrs].ptr = p;
    memMap[nptrs].file = file;
    memMap[nptrs].line = line;
    ++nptrs;
  }
  if (traceFlag) 
  {
    printf("Allocated %u bytes at address %p ", siz, p);
    printf("(file: %s, line: %ld)\n", file, line);
  }
  return p;
}

// Overload array new
void* operator new[](size_t siz, const char* file,
  long line) {
  return operator new(siz, file, line);
}

// Override scalar delete
void operator delete(void* p) 
{
  if (findPtr(p) >= 0) 
  {
    free(p);
    assert(nptrs > 0);
    delPtr(p);
    if (traceFlag)
      printf("Deleted memory at address %p\n", p);
  }
  else if (!p && activeFlag)
    printf("Attempt to delete unknown pointer: %p\n", p);
}

// Override array delete
void operator delete[](void* p) {
  operator delete(p);
} /**////:~

 二 说明：
1）通过重载new和delete来实现
2）使用时需要在工程中加入MemCheck.h和MemCheck.cpp，在需要检测的文件的前面include “MemCheck.h”，但是必须在所有的include的最后。
3）MEM_ON（），MEM_OFF（）用来打开或关闭检测
4）TRACE_ON（），和TRACE_OFF（）用来打开或关闭检测结果的输出
5）可以检测代码中使用了流，标准容器，以及某个类的构造函数分配了空间

三 使用实例：
console 的project中加入下面的file：

// MemoryLeak3.cpp : Defines the entry point for the console application.
//

#include <iostream>
#include <vector>
#include <cstring>

#include "MemCheck.h"   // Must appear last!
using namespace std;

void Test()
{
    int *i = new int(0);
}

class MyClass
{
private:
    int *p;
public:
    MyClass()
    {
        if(p != NULL)
        {
            p = new int(0);
        }
    }
    ~MyClass()
    {
        if(p != NULL)
        {
            delete p;
            p = NULL;
        }
    }
};

void Test2()
{
    int *i = NULL; // better for read
        i = new int(0);    
        int *&y = i; // pointer's reference
        delete i;

        MyClass *pMyClass = new MyClass();

        std::vector<MyClass*> myClasses;
        myClasses.push_back(new MyClass());
        myClasses.push_back(new MyClass());

        std::vector<void*> myVector;
        myVector.push_back(new MyClass());
        myVector.push_back(new MyClass());
        delete (MyClass *)(myVector.at(0));
        delete myVector.at(1); // memory leak
}

class Foo 
{
  char* s;
public:
  Foo(const char*s ) 
  {
    this->s = new char[strlen(s) + 1];
    strcpy(this->s, s);
  }
  ~Foo() 
  {
    delete [] s;
  }
};
void Test3()
{
    cout << "hello\n";
    int* p = new int;
    delete p;
    int* q = new int[3];
    delete [] q;
    int* r;
    /**//*delete r;*/
    vector<int> v;
    v.push_back(1);
    Foo s("goodbye");
}
int main() 
{
    TRACE_OFF();
    MEM_ON();
    Test();
    Test2();
    Test3();
    MEM_OFF();
} /**////:~

 四 测试结果如下