rt，显示ld returned 1 exit status和main.cpp:(.text+0xe): undefined reference to sayhello()'

代码：

//hello.h
#ifndef HELLO_H
#define HELLO_H
void sayhello();
#endif

//hello.cpp
#include<iostream>
#include"hello.h"
void sayhello(){
	std::cout<<"hello";
}

//main.cpp
#include"hello.h"
using namespace std;
int main(){
	sayhello();
	return 0;
}