error：Undefined symbols for architecture x86_64

writer：lIcht                      email：lIcht.gzl@gmail.com                 date:  2019.10.6

    出现原因：使用sublime3学习c++时面向对象时出现的编译错误，编译方式为macos终端命令行使用g++实现编译运行。

    error内容：

​x
Undefined symbols for architecture x86_64:
  "_main", referenced from:
     implicit entry/start for main executable
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
[Finished in 0.4s with exit code 1]

    代码：

main.cpp:

xxxxxxxxxx
#include <iostream>
#include "Student.h"
​
using namespace std;
​
int main(int argc, char const *argv[])
{
  Student stu1;
  Student stu2(5);
  Student stu3("sda", "asdiisd")
  return 0;
}

Student.h:

#ifndef STUDENT_H
#define STUDENT_H
#include <iostream>
using namespace std;
class Student
{
  public:
    Student();
    Student(int);
    Student(string, string);
    ~Student();
​
    void ShowInfo();
    string GatName() {return m_Name; }
    void SetName(string val) {m_Name = val; }
    string Getdesc() {return m_desc; }
    void Setdesc(string val) {m_desc = val; }
    int Getage() {return m_age; }
    void Setage(int val) {
      if(val < 0){
        m_age = 18;
      }else{
        m_age = val;
      }
    }
​
  protected:
​
  private:
    string m_Name;
    string m_desc;
    int m_age;
};
​
#endif// STUDENT_H

Student.cpp:

#include "Student.h"
​
Student::Student()
{
  cout << "默认构造" << endl;
}
​
Student::Student(int age)
{
  Setage(age);
  cout << "调用带参构造 Student::Student(int age)" << endl;
}
​
Student::Student(string name, string desc)//赋值，初始化参数列表的写法
{
  SetName(name);
  Setdesc(desc);
  cout << "调用带参构造 Student::Student(string name, string desc)" << endl;
}
​
Student::~Student()
{
  cout << "该对象被释放" << endl;
}

解决方法1：简单方法：将main.cpp中引用的头文件名称：#include "Student.h"改为：#include "Student.cpp"。

解决方法2：在sublime3中使用cltr+b运行main.cpp时是只会编译main.cpp的执行文件的，没有链接和编译Student.cpp的可执行文件，这时需要手动进行创建Student.cpp的可执行文件，输入如下代码行：g++ main.cpp Student.cpp -o Student。

解决成果：

xxxxxxxxxx
默认构造
调用带参构造 Student::Student(int age)
调用带参构造 Student::Student(string name, string desc)
该对象被释放
该对象被释放
该对象被释放
[Finished in 0.4s]