If you enable the clang warning "-Wweak-vtables" on any particular library in the system, you'll see dozens of classes in each Library that fire this warning. In particular, LibCore, LibJS, LibWeb and LibGUI

Why does this matter? Well, it only matters if the specific class you want to use is:

• Polymorphic (it has at least one virtual function)
• In a library that is dlopend at runtime, after the dynamic loader has resolved symbols for the main exectuable
  AND:
  • The target of a dynamic_cast OR
  • The target of a catch clause

This doesn't apply to .. most of our libraries, in most cases.

However! It does apply on Android. On Android, native libraries must be loaded via System.loadLibrary after the android runtime has initialized your application. This means that if we use dlopen (which System.loadLibrary does under the hood) to load ladybird.so or webcontent.so (which is mandatory), and then those shared libraries depend on our standard shlibs like liblagom-web.so, liblagom-js.so, any dynamic_casts across shlib boundaries will fail.

For more on why, see https://developer.android.com/ndk/guides/common-problems#rttiexceptions_not_working_across_library_boundaries

The net result is that we must compile Lagom as static libraries on Android. This isn't the end of the world, but it also means that if we add dlopen to our apps at any time in the future, we need to make 100% sure that any classes that have dynamic_cast() applied to them in the dynamically opened shlib have key functions or are not polymorphic.

I'm not sure how worth it is to actually fix this, unless we start running into problems with libs that must be dlopened.