FYI. To get clang-3.4 to build on 10.9, I had to modify the port file to set the isysroot to the 10.9 SDK. the build fails because it can’t find system framework headers. add the following flag to the configure script invocation: --with-default-sysroot=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk