I checked out llvm, clang, and compiler-rt, then ran the following command to generate an Xcode project: % pwd /Users/Shared/objc-namespaces/llvm % mkdir CMakeRoot % cd CMakeRoot % cmake -G Xcode -DLLVM_TARGETS_TO_BUILD="X86" ../ I opened the resulting LLVM.xcodeproj and tried to build the ALL_BUILD target. It failed while trying to build asan: clang: error: invalid argument '-mmacosx-version-min=10.9' not allowed with '-mios-simulator-version-min=7.0' Command /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang failed with exit code 1 Is this a known problem? --Kyle Sluder