cpp, Using it to process shell scripts

[Guy Harris]

>When using cpp to process the source to a script file, cpp always
>puts a blank line in the output for everytime it encounters a
>#directive or a /*comment*/.  (This is SunOS 4.1)  Is this normal
>behavior?

Yes.

>If so, why?

It's the way the S5R3 C preprocessor, upon which the SunOS 4.x one is
based, happens to sync up line numbers.  I've seen cases where older
pre-processors caused the compiler to get line numbers wrong, and where
the later one doesn't.

>It really makes the resulting shell script messy with all those blank
>lines...

"cpp" stands for C Pre-Processor, not "shell script preprocessor" nor
"Makefile preprocessor".  The fact that it happens to be usable, in some
cases, for other languages is pure serendipity.

>My manual suggests m4 as an alternative but I'm not sure it won't
>do the same thing.  More importantly, this is a X11 shell script
>with an Imakefile with all the predefined rules pointing to cpp
>already.
>
>If m4 is the correct choice, why didn't MIT choose to use it?

Dunno.  They may switch to using the DECUS C preprocessor, which comes
on recent (and perhaps not-so-recent) X11 source tapes, which means
they'll no longer be depending so much on the kindness of strangers. 
You might want to look into doing the same.