C preprocessor: documentation and use outside of the C compiler

[Ken Turkowski]

Is there any documentation anywhere about the C preprocessor, or does
one need to read through the source code to find out how to use it
outside of the C compiler?  I'm on a 4.2bsd UNIX system, if that makes
any difference.

One of the things that I'd like to do is to run the preprocessor on a
file, recognizing #ifdefs and including those files that would get
included based on the status of #define'ed variables, but I do not want
to make the macro substitutions in the resultant output.

In other words, I'd just like to conditionally unroll the #include's,
without touching the #defines.  Can the C preprocessor do this?
-- 
Ken Turkowski @ CADLINC, Palo Alto, CA
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