Well, this is a false question. The ABI didn't break; GCC5 deliberately supports both the old pre-C++11 and new C++11 ABIs in the same library. There are vari

Well, this is a false question. The ABI didn't break; GCC5 deliberately supports both the old pre-C++11 and new C++11 ABIs in the same library. There are various arguments for and against this approach, but the bottom line is that binary compatibility was explicitly not broken. The issue here is solely that clang++ doesn't yet implement some of the requirements of the new ABI and so isn't fully compatible with it. This is a very different point.