ifdef filter

[Brent P. Callaghan]

> 
> It often happens that software packages are set up to run on so many
> configurations that it is hard to read the code because of all the ifdefs.
> I would like a filter for C programs that does something like the
> following:
> 
> Invoke it like this:
> 
> 	prog <x.c >x.c.new -DSYSV -D68000
> 
> That is, filter out everything that is not going to be expanded by cpp while
> retaining the ifdefs that are going to be expanded, just for comment value.
> Ideally the output, when compiled, would produce exactly the same results as the
> original.  Does anyone have anything like this?

How about something simple like the following shell/awk one-liner:

          awk "/# *ifdef.*$1/ , /#endif/ {print}" $2

Call it "ifdef" and invoke as:

	  ifdef 6800  x.c  >  x.c.new

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