请问一下这个报错怎么解决呀？

[Error] passing 'const Stock' as 'this' argument of 'void Stock::show()' discards qualifiers [-fpermissive]

#include <iostream>
#include <string>
using namespace std;

class Stock{
    private:
        string name;
        int in_hand;
        double price;
        double total;
        void sum() {total =  in_hand * price;};
        
    public:
    Stock(const string &name_, int in_hand_ = 0, double price_ = 0);
    void buy_share(int add_number);
    void sold_out(int lower_number);
    void float_move(double change);
    void show();
    const Stock &decision(const Stock &s)const {
    return total > s.total?  *this : s;
     } 
}; 

int main(){

        const Stock company[4]={
        Stock("中国石油",10,20),
                          Stock("中国基金",20,67.8),
                          Stock("上海银行",30,45.6),
                          Stock("中外合作",20,67.8),
                          };
          const Stock *pointer = &company[0];    
                          
        for(auto i = 1; i < 4 ;i++){
            pointer = &pointer->decision(company[i]);
        } 
        /*int a = 0, b = 0;
        double c = 0;*/

    
        /*winner.buy_share(a);
        winner.sold_out(b);
        winner.float_move(c);*/
        pointer->show();
    
    return 0;
}

for循环感觉自己应该是让一个指针指向一个对象的地址，可是不知怎么的就是错。

静态对象只能调用静态成员函数

    void show()；
  //改成
    void show()const;