From: Boris Kolpackov (boris_at_[hidden])
Date: 2022-04-05 13:51:20
John Maddock via Boost <boost_at_[hidden]> writes:
> 1) Is there any existing best practice we should follow yet?
AFAIC, there is no practical, real-world experience using C++20 modules
in a substantial codebase. In fact, out of the big three compilers, only
MSVC has usable C++20 modules implementation (or claims to have; last
time I tried it, which was admittedly a while ago, it wasn't).
> 2) Can we share code content effectively between headers and modules? And
> by modules I mean "proper" ones: we should be able to write "import
> boost.whatever;" rather than importing a header.
As an experiment, I've tried to do this using the preprocessor in a
smallish library and it degenerated into an unmaintainable mess faster
than I expected.
IMO, the two viable options are:
1. Drop headers and focus on modules only.
2. Find an automated way (likely by the build system) to translate
(sensibly written) module interfaces to headers. I have some
ideas on this in the context of build2.
Note that I don't consider the "just re-export the header unit"
approach "modularization" since you don't really use any of
modules mechanisms.
> 8) Is there demand for this?
I think there will be if/when C++20 modules are well supported by
the compilers. However, modularizing Boost will be a big (and largely
thankless) undertaking. Perhaps the more realistic first step would
be to make sure public Boost headers are importable.