Re: [boost] [config][preprocessor] proposal for GCC-XML support

From: Paul Mensonides (pmenso57_at_[hidden])
Date: 2006-01-07 20:55:56

> -----Original Message-----
> From: boost-bounces_at_[hidden] 
> [mailto:boost-bounces_at_[hidden]] On Behalf Of Brad King

> > How does this effect the preprocessor library--aside from avoiding 
> > workarounds that GCC will report as ill-formed?
> 
> I don't think it does, but Dave Abrahams asked me to get your 
> attention by mentioning the preprocessor library:
> 
> http://www.gccxml.org/pipermail/gccxml/2006-January/000698.html
> 
> I think my post on the gccxml list used slightly confusing 
> wording and Dave thought this required only preprocessor 
> parsing work-arounds.
> However, I wasn't sure if he was implying that you were the 
> right person to make all the changes.  Sorry for the confusion.

Well, the pp-lib presents the same interface on all supported preprocessors.  If
something cannot be ported (via workarounds) to a particular preprocessor, the
mechanism simply isn't exposed as an interface, though the pp-lib implementation
itself may use it internally.  There are a few internal interfaces that are
really useful that aren't presented as external interfaces.  Some of those are
used by users anyway.  That's fine; I've recommended it many times along with
the portability warning.  However, there is nothing in the pp-lib that gcc's
preprocessor can't handle--it is a very good preprocessor--with the exception of
workarounds present for broken preprocessors.  Some of those workarounds involve
code that is either illegal or utilitizes undefined behavior.  Explicitly
catching __GCCXML__ should prevent the library from using any of these
workarounds in the pp-lib itself.  However, I obviously can't guarantee anything
about what clients of the pp-lib might be doing for portability.

> > Changing that is simple enough for the preprocessor 
> library.  Already 
> > done--the configuration recognizes __GCCXML__ and defines 
> > BOOST_PP_CONFIG_FLAGS accordingly.
> 
> Great, thanks.

No problem.

Regards,
Paul Mensonides