map的erase()释放内存

STL中的map调用erase(it)，当value值为指针时，释放内存：

 #include <iostream>
 #include <map>
 #include <string>

 using  namespace std;
 struct value{
     int i;
     std::string test;
 };

 int main()
 {
     std::map<int, value*> test_map;
     for(int i=; i<; ++i){
         value* tmp = new value();
         tmp->i = i;
         tmp->test = "test";
         test_map.insert(make_pair(i, tmp));
     }   

     for(std::map<int, value*>::iterator it=test_map.begin(); it!=test_map.end();){
         std::cout << "first " << it->first << " second " << (it->second)->i <<" "<< (it->second)->test << std::endl;
         delete it->second;
         it->second = NULL;
//test_map.erase(it);     //迭代器失效；
   test_map.erase(it++);   //防止迭代器失效，切记、切记
     }   

     return ;
 }

 root@u18:~/cp/test# g++ map3.cpp  -g -Wall
 root@u18:~/cp/test# ls -lt a.out
 -rwxr-xr-x  root root  Jul   : a.out
 root@u18:~/cp/test# valgrind  --tool=memcheck  --leak-check=full ./a.out
 ==== Memcheck, a memory error detector
 ==== Copyright (C) -, and GNU GPL'd, by Julian Seward et al.
 ==== Using Valgrind-3.7. and LibVEX; rerun with -h for copyright info
 ==== Command: ./a.out
 ====
 first  second  test
 first  second  test
 first  second  test
 first  second  test
 first  second  test
 first  second  test
 first  second  test
 first  second  test
 first  second  test
 first  second  test
 ====
 ==== HEAP SUMMARY:
 ====     in use at exit:  bytes in  blocks
 ====   total heap usage:  allocs,  frees,  bytes allocated
 ====
 ==== All heap blocks were freed -- no leaks are possible
 ====
 ==== For counts of detected and suppressed errors, rerun with: -v
 ==== ERROR SUMMARY:  errors from  contexts (suppressed:  from )