clang problems

Some days ago I tried to update the Cups source and got a message from configure saying that the C compiler (clang) couldn't create executables. In fact, starting clang caused this error message: ----- clang: /usr/bin/../lib/libstdc++.so.6: version `GLIBCXX_3.4.20' not found (required by clang) ----- I tried to re-compile clang, which of course failed at first, as it tried to compile itself with itself. After uninstalling clang I could re-compile it with gcc. Now the command `clang' produces this: ----- clang: symbol lookup error: clang: undefined symbol: _ZN4llvm9DebugFlagE ----- I wouldn't call this an improvement... Any ideas what could be wrong here? - Bernd