I'm seeing an ld warning building JavaScriptCore. > Ld /Volumes/Data/Build/Debug/JavaScriptCore.framework/Versions/A/JavaScriptCore normal x86_64 > cd /Volumes/Data/Code/safari/OpenSource/Source/JavaScriptCore > /Applications/Xcode.app/Contents/Developer/Toolchains/OSX10.9.xctoolchain/usr/bin/clang++ -arch x86_64 -dynamiclib -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.Internal.sdk -L/Volumes/Data/Build/Debug -F/Volumes/Data/Build/Debug -filelist /Volumes/Data/Build/JavaScriptCore.build/Debug/JavaScriptCore.build/Objects-normal/x86_64/JavaScriptCore.LinkFileList -Xlinker --no-demangle -install_name /System/Library/Frameworks/JavaScriptCore.framework/Versions/A/JavaScriptCore -mmacosx-version-min=10.9 -lobjc -Wl,-Y,3 -Wl,-unexported_symbol -Wl,__ZTISt9bad_alloc -Wl,-unexported_symbol -Wl,__ZTISt9exception -Wl,-unexported_symbol -Wl,__ZTSSt9bad_alloc -Wl,-unexported_symbol -Wl,__ZTSSt9exception -Wl,-unexported_symbol -Wl,__ZdlPvS_ -Wl,-unexported_symbol -Wl,__ZnwmPv -Wl,-unexported_symbol -Wl,__ZNKSt3__18functionIFvvEEclEv -Wl,-unexported_symbol -Wl,__ZNSt3__18functionIFvvEEC1EOS2_ -Wl,-unexported_symbol -Wl,__ZNSt3__18functionIFvvEEC2EOS2_ -Wl,-unexported_symbol -Wl,__ZNKSt3__18functionIFvRN3JSC17BytecodeGeneratorEPNS1_10RegisterIDEEEclES3_S5_ -Wl,-unexported_symbol -Wl,__ZNSt3__18functionIFvRN3JSC17BytecodeGeneratorEPNS1_10RegisterIDEEED1Ev -Wl,-unexported_symbol -Wl,__ZNSt3__18functionIFvRN3JSC17BytecodeGeneratorEPNS1_10RegisterIDEEED2Ev -Wl,-unexported_symbol -Wl,__ZNSt3__18functionIFvvEED1Ev -Wl,-unexported_symbol -Wl,__ZNSt3__18functionIFvvEED2Ev -Wl,-unexported_symbol -Wl,__ZTVNSt3__117bad_function_callE -Wl,-all_load -sub_library libobjc -framework CoreServices -stdlib=libc++ -fobjc-link-runtime -framework CoreFoundation -framework Foundation -licucore -lobjc -lWTF -lz -single_module -compatibility_version 1 -current_version 538.12 -Xlinker -dependency_info -Xlinker /Volumes/Data/Build/JavaScriptCore.build/Debug/JavaScriptCore.build/Objects-normal/x86_64/JavaScriptCore_dependency_info.dat -o /Volumes/Data/Build/Debug/JavaScriptCore.framework/Versions/A/JavaScriptCore > ld: warning: could not create compact unwind for _callToJavaScript: register saved more than once (might be shrink wrap)