Question

1. If any, what are the (obviously ignored by GCC) comments below called?
2. How do I get rid of them?

Here:

eisbaw@leno:~/GCC$ cpp < /dev/null
# 1 "<stdin>"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "<stdin>"
eisbaw@leno:~/GCC$ 

Answer 1

They are called linemarkers and you can use -P to have cpp or gcc omit them.

They are described in the Preprocessor Output section of the cpp manual.

And I agree with user30997 that you probably don’t want to get rid of them. They are ignored by gcc in the sense that they do not affect the compilation process, but they do provide useful diagnostic information when your code does not compile correctly.