Just an update on this answer:
This step is very important!
Ensure that C++ Standard Library is set to libstdc++ (GNU c++ standard library) in the Apple LLVM 5.0 Compiler Build Settings
Background:
I have an iOS app that abruptly stopped building for iOS 7 with standard library link errors. I had been testing the app successfully on the simulator and on an iPad mini, and archived it as well, but when I added an iPhone 5S for testing, I started getting link errors (possibly because of a new architecture in the mix?).
Searching the link errors on Google, I found advice to explicitly add libstdc++.dylib to the linked libraries. This did not work.
I experimented by adding libstdc++.6.dylib to the linked libraries instead; this eliminated the link errors, but the app crashed in the standard C++ library code very early.
Removing the explicit additions of the library and changing the compiler setting in Build Settings, as noted above, corrected the link errors and runtime problem.
Thanks to rimestad for the pointer!