On Tue, 9 Jun 1998 rhialto@polder.ubc.kun.nl wrote:

> In <Pine.NEB.3.95.980609110228.206W-100000@apb.iafrica.com> Alan Barrett 
> <apb@iafrica.com> writes:
> 
> >Mike Long <mikel@shore.net> said:
> >> Multiple inclusion protection does not keep cpp from reading the whole
> >> header each time it is #included.
> >
> >This is just a SMOP.  Nothing prevents the compiler from noticing when a
> >file consists entirely of comments, blank lines, and [...]
> 
> And in fact, cccp (gnu's cpp) already does this.

The main problem with this reasoning is that cpp only knows this for a
single invocation. I don't know about you, but compiling one source file
and that may have one or two files included multiple times is simply _not_
a concern.  The real issue is having headers pull in other headers (which
may pull in other headers)... think `how much output from cpp is cc1 going
to have to chew on?'  Now, multiply this processing time by N source
files.

--scott