C++自定义类存入unordered_set触发段错误问题求助

我正在学习游戏六边形地图开发教程，原教程用struct实现六边形字段，我改成HexagonField类后编译正常，但调用std::unordered_set的insert方法插入实例时触发段错误，怀疑哈希函数有误，找不到排查方向，求解决。

main.c #

#include <unordered_set>
#include "hexagonField.hpp"

int main(int argc, char **argv)
{
    std::unordered_set <HexagonField> map;
    map.insert(HexagonField(0, 0, 0));
            
    return 0;
}

hexagonField.hpp #

#ifndef HEXAGON_H
#define HEXAGON_H
#include <assert.h>
#include <vector>

class HexagonField
{
public:
    const int q, r, s;
    HexagonField(int q, int r, int s);
    ~HexagonField();
    HexagonField hexagonAdd(HexagonField a, HexagonField b);
    HexagonField hexagonSubtract(HexagonField a, HexagonField b);
    HexagonField hexagonMultiply(HexagonField a, int k);
    int hexagonLength(HexagonField hex);
    int hexagonDistance(HexagonField a, HexagonField b);
    HexagonField hexagonDirection(int direction /* 0 to 5 */);
    HexagonField hexagonNeighbor(HexagonField hex, int direction);

    const std::vector<HexagonField> hexagonDirections = {
    HexagonField(1, 0, -1), HexagonField(1, -1, 0), HexagonField(0, -1, 1),
    HexagonField(-1, 0, 1), HexagonField(-1, 1, 0), HexagonField(0, 1, -1)
    };

    bool operator == (const HexagonField comparedHex) const
    {
        return this->q == comparedHex.q && this->r == comparedHex.r && this->s == comparedHex.s;
    }
    bool operator != (const HexagonField comparedHex) const
    {
        return !(*this == comparedHex);
    };
};

namespace std
{
  template<>
    struct hash<HexagonField>
    {
      size_t operator()(const HexagonField & obj) const
      {
        return hash<int>()(obj.q);
      }
    };
}
#endif

hexagonField.cpp #

#include "hexagonField.hpp"

HexagonField::HexagonField(int q, int r, int s): q(q), r(r), s(s)
{
    assert (q + r + s == 0);
}

HexagonField HexagonField::hexagonAdd(HexagonField a, HexagonField b)
{
    return HexagonField(a.q + b.q, a.r + b.r, a.s + b.s);
}

HexagonField HexagonField::hexagonSubtract(HexagonField a, HexagonField b)
{
    return HexagonField(a.q - b.q, a.r - b.r, a.s - b.s);
}

HexagonField HexagonField::hexagonMultiply(HexagonField a, int k)
{
    return HexagonField(a.q * k, a.r * k, a.s * k);
}

int HexagonField::hexagonLength(HexagonField hex) {
    return int((abs(hex.q) + abs(hex.r) + abs(hex.s)) / 2);
}

int HexagonField::hexagonDistance(HexagonField a, HexagonField b) {
    return hexagonLength( hexagonSubtract(a, b));
}

HexagonField HexagonField::hexagonDirection(int direction /* 0 to 5 */) {
    assert (0 <= direction && direction < 6);
    return hexagonDirections[direction];
}

HexagonField HexagonField::hexagonNeighbor(HexagonField hex, int direction) {
    return hexagonAdd(hex, hexagonDirection(direction));
}

核心问题：无限递归构造导致栈溢出 #

段错误的根源不是哈希函数，而是类中的hexagonDirections被定义为非静态成员变量。每个HexagonField实例构造时，都会初始化这个vector，而vector中的6个HexagonField元素又会各自构造自己的hexagonDirections，形成无限递归构造，最终导致栈溢出触发段错误。

另外，当前的成员函数设计也不合理：比如hexagonAdd、hexagonDirection这类工具函数不需要依赖当前实例的状态，应该改为静态成员函数，避免误用。

修复步骤： #

1. 将hexagonDirections改为静态成员变量
   在头文件中声明为static，并在cpp文件中定义初始化，确保所有实例共享一份：

   • 修改hexagonField.hpp中的声明：

     class HexagonField
     {
     public:
         // ... 其他成员 ...
         static const std::vector<HexagonField> hexagonDirections;
         // ... 其他成员 ...
     };
     

   • 在hexagonField.cpp中添加定义：

     const std::vector<HexagonField> HexagonField::hexagonDirections = {
         HexagonField(1, 0, -1), HexagonField(1, -1, 0), HexagonField(0, -1, 1),
         HexagonField(-1, 0, 1), HexagonField(-1, 1, 0), HexagonField(0, 1, -1)
     };
     

2. 将工具类成员函数改为静态函数
   像hexagonAdd、hexagonDirection这类不需要访问当前实例的函数，声明为static：

   • 修改hexagonField.hpp中的函数声明：

     static HexagonField hexagonAdd(HexagonField a, HexagonField b);
     static HexagonField hexagonSubtract(HexagonField a, HexagonField b);
     static HexagonField hexagonMultiply(HexagonField a, int k);
     static int hexagonLength(HexagonField hex);
     static int hexagonDistance(HexagonField a, HexagonField b);
     static HexagonField hexagonDirection(int direction /* 0 to 5 */);
     static HexagonField hexagonNeighbor(HexagonField hex, int direction);
     

   • cpp文件中的函数体无需修改，保持原有逻辑即可。

3. 补充析构函数实现
   头文件中声明了~HexagonField();但未实现，需在hexagonField.cpp中补充：

   HexagonField::~HexagonField() = default;
   

4. 优化哈希函数（可选但推荐）
   当前哈希函数仅使用q字段会导致大量冲突，可结合三个字段生成更均匀的哈希值：

   namespace std
   {
     template<>
       struct hash<HexagonField>
       {
         size_t operator()(const HexagonField & obj) const
         {
           size_t h1 = hash<int>()(obj.q);
           size_t h2 = hash<int>()(obj.r);
           size_t h3 = hash<int>()(obj.s);
           return h1 ^ (h2 << 1) ^ (h3 << 2);
         }
       };
   }
   

验证 #

完成以上修改后重新编译运行，map.insert(HexagonField(0,0,0))将正常执行，不会触发段错误。

内容的提问来源于stack exchange，提问作者Desfell