如何找到任何对象使用的内存

问题描述

class Help
{
public:
        Help();
        ~Help();

        typedef std::set<string> Terms;
        typedef std::map<string, std::pair<int,Terms> > TermMap;
        typedef std::multimap<int, string, greater<int> > TermsMap;

private:

        TermMap  terms;
        TermsMap    termsMap;
};

我们如何找到term 和termsMap 对象使用的内存(以字节为单位).我们有图书馆吗?

How can we find the memory used (in bytes) by the objects term and termsMap. Do we have any library ?

推荐答案

如果您正在寻找对象的完整内存使用情况，这在 C++ 中通常无法解决 - 而我们可以获得实例的大小通过 sizeof() 自身，对象总是可以根据需要动态分配内存.

If you are looking for the full memory usage of an object, this can't be solved in general in C++ - while we can get the size of an instance itself via sizeof(), the object can always allocate memory dynamically as needed.

如果你能找出一个容器中单个元素有多大，你就可以得到一个下限:

If you can find out how big the individual element in a container are, you can get a lower bound:

size = sizeof(map<type>) + sum_of_element_sizes;

请记住，容器仍然可以分配额外的内存作为实现细节，对于像 vector 和 string 这样的容器，您必须检查 分配大小.

Keep in mind though that the containers can still allocate additional memory as an implementation detail and that for containers like vector and string you have to check for the allocated size.

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