Advice on C++20 modules (Boost)

[ben.boeckel (Ben Boeckel (Kitware))]

As long as any possible ABI symbol is present in the library the boost_asio library provides (including module initializers), things should be fine. If everything is inline, then the library just needs to provide module initializers for every possible module.

@anarthal

In a module world, the user would need to have a way to specify which of these macros need to be defined when building their Asio module.

I’m not sure how this will look in CMake, but I suspect that something needs to be done as the only place is -D on the command line. Maybe something like:

#if __has_include(<boost/asio/user/config.hpp>)
#include <boost/asio/user/config.hpp>
#endif
// Polyfills anything not specified with defaults.
#include <boost/asio/default/config.hpp>

?