I'd be wary of concluding that "if it works on Apple Clang, it will work on all Clangs". I've seen this to be untrue in multiple cases and the root cause can be

I'd be wary of concluding that "if it works on Apple Clang, it will work on all Clangs". I've seen this to be untrue in multiple cases and the root cause can be found in a multitude of locations. LLVM, Clang, libc (glibc, musl, MSVC, Apple libC,), C++ STL (libstdc++, libc++, MSVC), compiler-rt, platform ABI (Apple ABI's are pretty much SysV, except when they aren't...), and of course the actual version/branch of all of these things. It is certainly a start but unfortunately an over-generalization. :)