Re: The Future of C++ and Boost - C++ Modules

From: Peter Dimov (pdimov_at_[hidden])
Date: 2022-05-13 21:16:26

Robert Ramey wrote:
> On 5/13/22 5:24 AM, Peter Dimov via Boost wrote:
> > John Maddock wrote:
> 
> >> I'm afraid my conclusion is that modules are simply not yet ready for
> >> prime time.
> >
> > If they ever are.
> >
> > Modules can work for leaf libraries, but for libraries used as
> > dependencies by other libraries, you'll encounter a situation where
> > the same translation unit imports boost.lib or "boost/lib.hpp" in one
> > place and then includes "boost/lib/something.hpp" in another, which is
> > probably never going to work correctly.
> 
> This is sounds like how I thought it had to work to be effective.  If I understand
> this correctly, the whole modules concept is in fundamental conflict with the
> anything which uses the boost inclusion/dependency model - which is every
> module includes what it uses and nothing else.
> 
> In my view the whole modules idea is misconceived.  One more nail in coffin of
> C++ xx standard libraries.
> 
> It's time for use to seriously start moving on.

Looks like I was mistaken, though. At least with header units, i.e.
`import "boost/lib.hpp"`, it all seems to "just work" under MSVC. That is, the
compiler automatically merges the identical definitions from the sub-#includes.