派生类析构会调用基类析构吗

定义一个document类，有数据成员name，表示文档名称。从document派生出book类，增加数据成员pagecount，表示书籍页数。在构造函数和析构函数中输出信息，观察基类与派生类的构造函数和析构函数的调用顺序。

代码如下：

#include <iostream>
#include <string>

using namespace std;

class document {
public:
    document(const string& name) : name_(name) {
        cout << "document constructor called: " << name_ << endl;
    }

    virtual ~document() {
        cout << "document destructor called: " << name_ << endl;
    }

protected:
    string name_;
};

class book : public document {
public:
    book(const string& name, int pagecount) : document(name), pagecount_(pagecount) {
        cout << "book constructor called: " << name_ << ", " << pagecount_ << " pages" << endl;
    }

    ~book() {
        cout << "book destructor called: " << name_ << ", " << pagecount_ << " pages" << endl;
    }

private:
    int pagecount_;
};

int main() {
    book b("The Lord of the Rings", 1178);
    return ;
}

输出结果如下：

document constructor called: The Lord of the Rings
book constructor called: The Lord of the Rings, 1178 pages
book destructor called: The Lord of the Rings, 1178 pages
document destructor called: The Lord of the Rings

可以看到，先调用基类的构造函数，再调用派生类的构造函数；先调用派生类的析构函数，再调用基类的析构函数。