Using libc++ on older system

Lion and Mountain Lion

Lion and Mountain Lion systems have libc++ installed with the OS but still use libstdc++ as the default C++ runtime. You can use it by passing -stdlib=libc++ as a command line argument to clang++, and you can instruct MacPorts to use it instead of libstdc++ as the default C++ runtime.

1. Start with a new install of MacPorts or uninstall all ports that use C++
2. Edit /opt/local/etc/macports/macports.conf to contain:

cxx_stdlib         libc++
buildfromsource    always
delete_la_files    yes

delete_la_files is not necessary, it is reccomended since you need to set buildfromsource.

Leopard and Snow Leopard

Leopard and Snow Leopard do not have libc++ installed by the OS, but MacPorts can build and install system roots that contain these runtimes for your use. After installing these roots (which is done automatically when the libcxxabi and libcxx ports activate), you can choose to continue using libstdc++ as the default C++ runtime in MacPorts or configure MacPorts to use the new libc++ runtime.

Bootstrapping: Install libc++ and libc++abi

1. Start with a new install of MacPorts or uninstall all ports that use C++
2. Install the libcxx port. When it activates, the libcxxabi and libcxx ports will install libc++.dylib and libc++abi.dylib (which will remain after you uninstall MacPorts). This will pull in a number of dependencies.

   sudo port -v -s install libcxx
   

3. Deactivate all your active ports (or at least the C++ ports) in order to prepare to rebuild them, and just activate the new toolchain:

   	sudo port -v -f deactivate active
   	sudo port -v install clang-3.4 ld64 cctools
   

4. Edit /opt/local/etc/macports/macports.conf to contain:

   cxx_stdlib         libc++
   buildfromsource    always
   delete_la_files    yes
   default_compilers  macports-clang-3.4 macports-clang-3.3 gcc-4.2 apple-gcc-4.2 gcc-4.0
   

5. Uninstall all the remaining inactive ports:

   sudo port -v -f uninstall inactive
   

6. Build a newer clang compiler using libc++ and uninstall the old one using libstdc++:

   sudo port -v install clang-3.5
   sudo port -v uninstall llvm-3.4 clang-3.4
   

7. Either:
   1. Edit /opt/local/etc/macports/macports.conf again to add macports-clang-3.5 before macports-clang-3.4.
   2. Rebuild clang-3.4 using clang-3.5:

      sudo port -v install clang-3.4 configure.compiler=macports-clang-3.5