https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80469
--- Comment #4 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
(In reply to Ubikovich from comment #3)
> >> You need to provide the definition of dothis() somewhere.
>
> There is the definition:
>
> // subimpl.cpp
> #include "subimpl.h"
> void A::dothis() {}
Yeah, put "__attribute__ ((visibility("default")))" above it and you're done.
