未定义的引用，未找到架构x86_64的符号

Question

我制作了这个简单的课程，我不知道为什么我会一直收到错误; 这是我的代码：

libgit2 returned: Invalid path for filesystem 'E:/Projects/vsteams/node_modules/gulp-imagemin/node_modules/imagemin/node_modules/imagemin-gifsicle/node_modules/gifsicle/node_modules/bin-build/node_modules/decompress/node_modules/decompress-tar/node_modules/strip-dirs/node_modules/is-natural-number/is-natural-number-cjs.js': Data area passed to a system call is too small.

这是主要的：

    using namespace std;

    class Player{
    public:
        Player(string name);
        virtual ~Player();
        virtual void fight() = 0;
    private:
        string _name;
    };       


    #include "Player.h"
    #include <iostream>
    using namespace std;

    class Elf : public Player{
    public:
         Elf(string elf_name);
        ~Elf();
        void fight(){
            cout << "I kill you!" << endl;
        }
    private:
        string _elf_name;
    };

    class Dwarf : public Player{
    public:
        Dwarf(string dwarf_name);
        ~Dwarf();
        void fight(){
            cout<< "Where's The Arkengem!?" << endl;
        }
    private:
        string _dwarf_name;
    };

这是错误信息：

架构x86_64的未定义符号：

“Elf :: Elf（std :: __ 1 :: basic_string，std :: __ 1 :: allocator＆gt;）”，引自：       _main in Principale.o

“Dwarf :: Dwarf（std :: __ 1 :: basic_string，std :: __ 1 :: allocator＆gt;）”，引自：       在Principale.o中的_main ld：找不到架构x86_64的符号

提前谢谢。