C++ std :: sort()调用析构函数

Question

我重载了我的类' ()运算符以将其用作排序比较器函数.当使用std :: sort()时,它由于某种原因多次调用类的析构函数(显然取决于向量中的条目数量).我在~RANK()中描述了更多.

#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(带注释析构函数):

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

Answer 1

std :: sort的比较函数按值传递.通过使用RANK对象作为比较器,您将副本传递给std::sort(作为最后一个值),并且它可以在内部多次复制它.

我建议从类RANK中分离掉COMBO的比较运算符