That is very easily solved by not using modules for those things that cause issues, or by using a module facade over traditional C++. For your example, you cou

That is very easily solved by not using modules for those things that cause issues, or by using a module facade over traditional C++. For your example, you could make a 'foo' module that pulls in an implementation from a traditional C++ source file, "armv5/foo_impl.h" or "x64/foo_impl.h", using preprocessor #if/#ifdef to choose the right one. Or you could even use a module backend, pulling in the implementation from either "foo_armv5.bmi" or "foo_x64.bmi".