c++ - 使用 std::map 时内存增长

Question

我观察到这段代码的内存增长。但它应该不会显示内存增长，因为所有创建的对象都被删除了。

我已经为 MyObj 实现了析构函数，并使用 gdb 观察到当迭代映射时析构函数实际上被调用了。有人可以解释我哪里做错了吗。

map<int,MyObj*> myMap;

for(int i = 1; i<= 500000; i ++) 
    {
        MyObj* pMyObj = new MyObj; 
        myMap.insert(pair<int,MyObj*>(i,pMyObj));

    }

map<int,MyObj*>::iterator ite = myMap.begin();
while (ite != myMap.end())
{

    delete ite->second;
    ite++;
}

myMap.clear();

Answer 1

您可能想阅读 http://www.gnu.org/software/libc/manual/html_node/Freeing-after-Malloc.html#Freeing-after-Malloc .特别是最后一段:

Occasionally, free can actually return memory to the operating system and make the process smaller. Usually, all it can do is allow a later call to malloc to reuse the space. In the meantime, the space remains in your program as part of a free-list used internally by malloc.

如果您希望将大块内存返回给操作系统，请考虑使用 mmap。