On Sun, Mar 8, 2020 at 2:01 PM Bryce Adelstein Lelbach aka wash via Ext <
ext_at_[hidden]> wrote:

> Do we have any ABI stability concerns regarding modularizing the standard
> library? Certainly for strong module ownership implementations, this is a
> concern, but for weak module ownership implementations it may be a concern
> too, because the mangling of internal implementation details with module
> linkage would change.
>
> Can implementations overcome this with special hacks for the standard
> library that preserve the old mangled names?
>

I don't expect stdlibs to move off of headers in the foreseeable future (in
order to support pre-modules compilers and build systems). Given this I
expect standard library entities to remain the in global module, and thus
the named module they are exported from to be irrelevant. If someone writes
a new C++20+ only stdlib then they will have a different ABI anyway, but
there would then be potential ABI breakage from moving an entity. However,
it is not observable which module an entity is from, so it's quite easy to
work around any ABI changes that would occur due to moving where an entity
is. I seriously doubt we would remove a declaration from a module without
removing the declaration entirely though, which is the only way you would
end up needing to change which module owns it.

- Michael Spencer