What is the reason for the following warning in some C++ compilers?
No newline at end of file
Why should I have an empty line at the end of a source/header file?
12 Answers
Think of some of the problems that can occur if there is no newline. According to the ANSI standard the #include of a file at the beginning inserts the file exactly as it is to the front of the file and does not insert the new line after the #include <foo.h> after the contents of the file. So if you include a file with no newline at the end to the parser it will be viewed as if the last line of foo.h is on the same line as the first line of foo.cpp. What if the last line of foo.h was a comment without a new line? Now the first line of foo.cpp is commented out. These are just a couple of examples of the types of problems that can creep up.
Just wanted to point any interested parties to James' answer below. While the above answer is still correct for C, the new C++ standard (C++11) has been changed so that this warning should no longer be issued if using C++ and a compiler conforming to C++11.
From C++11 standard via James' post:
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 (C++11 §2.2/1).
C++03 Standard [2.1.1.2] declares:
... If a source file that is not empty does not end in a new-line character, or ends in a new-line character immediately preceded by a backslash character before any such splicing takes place, the behavior is undefined.
The answer for the "obedient" is "because the C++03 Standard says the behavior of a program not ending in newline is undefined" (paraphrased).
The answer for the curious is here: http://gcc.gnu.org/ml/gcc/2001-07/msg01120.html.
It isn't referring to a blank line, it's whether the last line (which can have content in it) is terminated with a newline.
Most text editors will put a newline at the end of the last line of a file, so if the last line doesn't have one, there is a risk that the file has been truncated. However, there are valid reasons why you might not want the newline so it is only a warning, not an error.
#include will replace its line with the literal contents of the file. If the file does not end with a newline, the line containing the #include that pulled it in will merge with the next line.
In my case, I use KOTLIN Language and the compiler is on IntelliJ. Also, I am using a docker container with LINT to fix possible issues with typos, imports, code usage, etc. This error is coming from these lint fixes, most probably - I mean surely.
In short, the error says, 'Add a new line at the end of the file' That is it.
Before there was NO extra empty line:
Related