The file is a helloworld.cpp:

#include <iostream>
using namespace std;

int main() {
 if(true)
 cout << "!!!Hello World!!!" << endl; // prints !!!Hello World!!!
 return 0;
}

But when I build it,get a warning:

g++ -Wall -O2 -c -o hw.o hw.cpp
hw.cpp:8:2: warning: no newline at end of file
g++ -o myprog hw.o

If I add a newline at the end,the warning will go.

Why is that newline at end of file recommended in a cpp source file?