这个报错什么意思，找不到问题出在哪里了

正在学习类和接口分离与现实

题目是输入成绩，输出并求均值，要求用类和接口分离与现实

//.h头文件
#include 
class GradeList
{
public:
    explicit GradeList(std::string);
    void setGradeList(std::string);
    std::string getGradeList() const;
    void DisplayMessage() const;
    static void range() ;
private:
    std::string courseName;

};

//头文件配套.cpp
#include "GradeList.h"
#include 
#include

using namespace std;
GradeList::GradeList(string name)
{
    setGradeList(name);
}

void GradeList::setGradeList(string name)
{
    if (name.size() <= 25)
    {
            courseName = name;
    }
    else
    {
        courseName = name.substr(0, 25);
        cerr << "Name\"" << name << "\"exceeds maximum length" << endl;
    }
}

string GradeList::getGradeList()const
{
    return courseName;
}

void GradeList::DisplayMessage()const
{
    cout<<"Welcome to the grade list for\n"<<getGradeList()<<"!\n"<void GradeList::range()
{
    int total;
    total = 0;
    int i=1;
    while(i<=10)
    {
        cout<<"Enter grade:";
        int grade;
        grade=0;
        cin>>grade;
        total+=grade;
        i++;
    }
    int average;
    average = total/10;
    cout<<"\ntotal of all grades is"<"Class average is"<
//main函数
#include "GradeList.h"
int main()
{
    GradeList myGradeList("C++");
    myGradeList.DisplayMessage() ;
    myGradeList.range();
    return 0;
}

编译器报错，看不明白
[1/1] Linking CXX executable AverageGrade.exe
FAILED: AverageGrade.exe
collect2.exe: error: ld returned 1 exit status
ninja: build stopped: subcommand failed.

运行过一次，残留的后台进程没关？打开任务管理器看看。