静态成员函数c ++中的分段错误

Question

class Adder {
public:
    static int Solve(int a, int b) {return a + b;}
};

class Substructor {
public:
    static int Solve(int a, int b) {return a - b;}
};

class Comparer {
public:
    static bool Solve(int a, int b) {return a < b;}
};

class If {
public:
    static int Solve(bool term, int a, int b) {return term ? a : b;}
};

class Fibo {
public:
    static int Solve(int num) {
      int res =
      If::Solve(
        Comparer::Solve(num, 2),
        1,       
        Adder::Solve(
          Fibo::Solve(Substructor::Solve(num, 1)),
          Fibo::Solve(Substructor::Solve(num, 2))
        )
        
      );
      return res;
    }
};

int calc(int x) {
  return Fibo::Solve(x);
}

#include <iostream>
int main() {
  std::cout << calc(5) << '\n';
  return 0;
}

此代码导致分段错误。我分别测试了所有类，编写了没有其他静态成员函数的递归 fibo 静态成员函数并且它可以工作。结合时它会粉碎。如何修复它以及为什么它会损坏？

Answer 1

问题出在这里：

class Fibo {
public:
    static int Solve(int num) {
      int res =
      If::Solve(
        Comparer::Solve(num, 2),
        1,       
        Adder::Solve(
          Fibo::Solve(Substructor::Solve(num, 1)),
          Fibo::Solve(Substructor::Solve(num, 2))
        )
      );
      return res;
    }
};

在 If::Solve() 句子中，如果 Comparer::Solve(num, 2) 检查 num<2，return 1 并且不计算剩余的表达式 Fibo::Solve(Substructor::Solve(num, 1)) 和第二个，它不会像你预期的那样工作。要评估 If::Solve()，必须先评估每个参数才能传递给 If::Solve()。当它一次又一次地递归计算时，发生堆栈溢出，因此程序终止。如果你真的想做到运行，修改如下：

class Fibo {
public:
    static int Solve(int num) {
        if (Comparer::Solve(num, 3)) {
            return 1;
        }
        else return Adder::Solve(
            Fibo::Solve(Substructor::Solve(num, 1)),
            Fibo::Solve(Substructor::Solve(num, 2))
        );
    }
};

这保证如果 num 是 1 或 2，return 1 并且不会计算剩余的表达式。

静态成员函数c ++中的分段错误

Segmentation fault in static member function c++

c++

static-methods

segmentation-fault