FYI, clang ignores CPATH and LIBRARY_PATH. http://llvm.org/bugs/show_bug.cgi?id=8971 So that's fun, and could cause issues with some ports that have come to rely on MacPorts setting CPATH and LIBRARY_PATH, such as: https://trac.macports.org/ticket/30271 https://trac.macports.org/ticket/28220