C++ Standards (newline ending of source files)

Question

I am referring to: Why should text files end with a newline? One of the answers quotes the C89 standard. Which in brief dictates that a file must end with a new line, which is not immediately preceded by a backslash.

Does that apply to the most recent C++ standard?

#include <iostream>
using namespace std;

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

Is the above valid? (Assuming there is a newline after //\, which I've been unable to display)

Answer 1

The given code is legal in the case of C++, but not for C.

Indeed, the C (N1570) standard says:

Each instance of a backslash character (\) immediately followed by a new-line character is deleted, splicing physical source lines to form logical source lines. Only the last backslash on any physical source line shall be eligible for being part of such a splice. A source file that is not empty shall end in a new-line character, which shall not be immediately preceded by a backslash character before any such splicing takes place.

The C++ standard (N3797) formulates it a bit differently (emphasis mine):

Each instance of a backslash character (\) immediately followed by a new-line character is deleted, splicing physical source lines to form logical source lines. Only the last backslash on any physical source line shall be eligible for being part of such a splice. If, as a result, a character sequence that matches the syntax of a universal-character-name is produced, the behavior is undefined. A source file that is not empty and that does not end in a new-line character, or that ends in a new-line character immediately preceded by a backslash character before any such splicing takes place, shall be processed as if an additional new-line character were appended to the file.