Xcode 5.1 enable C++14
To get this to work, you first set "C++ Language Dialect" to "compiler default". Then in "Other C++ flags" add "-std=c++1y".
This will allow Clang++ to compile with c++14 from within Xcode. I tested this with Xcode 5.1.1 using the new user defined literal for basic_string:
std::string word = "hello"s;Update: As of Xcode 6, c++14 is available as a first-class language dialect.
With Xcode Version 8.2 (8C38) you click on the project name in the project navigator (click on the little folder at the left of the window to get to this) then in the middle pane of the ide, you click on build settings (up the top of the middle pane), then you can scroll to find the Apple LLVM 8.0 - Language - C++ section. There is a C++ Language Dialect section; select C++14 [-std-c++=14] from the spinner. This then compiles properly.