RE: [boost] preprocessed mpl code was Re: [mpl?] loki -> boost

From: Hartmut Kaiser (hartmutkaiser_at_[hidden])
Date: 2004-02-26 09:59:28

Sam Partington wrote:

> On Fri, 20 Feb 2004 16:09:56 -0500, David Abrahams 
> <dave_at_[hidden]> wrote:
> > There are pre-generated headers in boost/mpl/aux_/preprocessed/...
> > Those are the ones that actually get used.
> 
> What generates these files?  We use the preprocessor library 
> for boiler plate code here and there and find it very useful.
> 
> But one of the critisms voiced is that debugging the 
> generated code is 
> difficult->impossible (all debug info points at the same line in the
> code!).  What we really want is a way of preprocessing the 
> code as a separate stage in the build process.
> 
> We could (and occasionally do) output the preprocessed files, 
> but that means all of the headers are pulled in, and all of 
> the comments stripped out.

If you need or would like to debug your preprocessing code you may want to
have a look at the tracing capabilities provided by the Wave preprocessor.
It allows you to get a very dedicated macro expansion trace of a certain
macro, which allows to track down nasty pp problems (and BTW is very
educational, what actually is going on inside the Boost.PP library).

Regards Hartmut