C++ std::sort() 调用析构函数

Question

我重载了我的类的() 运算符以将其用作排序比较器函数。使用 std::sort() 时，出于某种原因，它多次调用类的析构函数(显然取决于 vector 中的条目数量)。我在 ~RANK() 中描述了更多内容。

#include <stdio.h>
#include <stdlib.h>
#include <vector>
#include <algorithm>

class RANK
{
    struct COMBO
    {
        int x;
    };

    std::vector<COMBO *> data;
public:
    RANK()
    {
        printf("RANK()\n");
    }

    ~RANK()
    {
        printf("~RANK()\n");

        /*
         * Here is the problem.
         * Since my vector consists of pointers to COMBO objects,
         * I delete them upon RANK object's destruction. However,
         * std::sort() calls RANK's destructor many times and
         * throws some runtime error, unless commented out.
         */
        //for (unsigned int i = 0, n = data.size(); i < n; i++)
        //  delete data[i];
    }

    void Add(int x)
    {
        COMBO *combo = new COMBO();
        combo->x = x;

        data.push_back(combo);
    }

    unsigned int Size()
    {
        return data.size();
    }

    void Sort()
    {
        std::sort(data.begin(), data.end(), *this);
    }

    int operator[](unsigned int pos)
    {
        return data[pos]->x;
    }

    bool operator()(COMBO *combo1, COMBO *combo2)
    {
        return combo1->x > combo2->x;
    }
};

int main()
{
    RANK rank;
    rank.Add(1337);
    rank.Add(9001);
    rank.Sort();

    for (unsigned int i = 0, n = rank.Size(); i < n; i++)
        printf("%d ", rank[i]);
        printf("\n");

    system("pause");

    return 0;
}

输出(带注释的析构函数):

RANK()
~RANK()
~RANK()
~RANK()
~RANK()
~RANK()
9001 1337

Answer 1

std::sort 的比较函数是按值传递的。通过使用 RANK 对象作为比较器，您将向 std::sort 传递一个拷贝(作为最后一个值)，它可能会在内部多次复制它。

我建议将 COMBO 的比较运算符从类 RANK 中分离出来