How do I get back c++0x/c++11 support for Mac OS X 10.6 deployment using Xcode 4.6.2 thru 7.1.1

Question

I heavily use the c++0x/c++11 features in my project, particularly code blocks and shared pointers. When I upgraded my OS to 10.8 Mountain Lion (Edit: From 10.7), I was forc

Answer 1

Apple has decided to only officially support libc++ on 10.7 or higher. So the version of clang/llvm that ships with Xcode checks to see if the deployment target is set for 10.6 when using libc++, and prevents you from compiling. However, this flag is not included in the open source version of clang/llvm.

Take a look at this thread: http://permalink.gmane.org/gmane.comp.compilers.clang.devel/17557

So, to compile a project that is using c++11 for 10.6 deployment, you need to give Xcode the open source version. Here is one way of doing it:

1. Download the open source version of clang from here (use LLVM 3.1 for Xcode 4.5.x; use LLVM 3.2 for Xcode 4.6.x; use LLVM 3.3 for Xcode 5.0.x; use LLVM 3.5.0 for XCode 6.0.1; use LLVM 3.7.0 for XCode 7.1.1): http://llvm.org/releases/download.html
   
2. Make a backup of Xcode's default clang compiler and put it in a safe place (In case you screw up!) This is located at: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang
3. Replace the default clang compiler with the one you downloaded from [1]
4. chown the clang binary for root:wheel with sudo chown root:wheel clang from the bin directory listed in [2].
5. Startup Xcode and compile!

UPDATE #1: This technique does not currently work for Xcode 5.1 or newer, which relies on LLVM 3.4. When I get some more time, I will try and find a solution to post here. But if someone comes up with a solution before me, they should post it as an answer.

UPDATE #2: Unfortunately I can't remember if I ever found a solution for Xcode 5.1, however I can confirm that the technique does still work for Xcode 6.0.1. I haven't tested on versions newer than that, but it could still work.

UPDATE #3: This technique appears to still work with XCode 7.1.1 using LLVM 3.7.0. However, the open source LLVM clang does not support Bitcoding. So you will need to switch between the open source compiler and Apple's compiler in order to develop for both 10.6 and tvOS/watchOS (which require Bitcoding).

P.S.: The Mac OS X binaries for LLVM 3.4 and 3.5.0 are listed as "Clang for Darwin 10.9" at www.llvm.org/releases/download.html rather than as "Clang Binaries for Mac OS X" in previous versions.