If you are a C++ developer and targeting your application for Mac OS X, this announcement may be relevant to you.
For some time we have provided two forms of libLeap.dylib, one that links with libstdc++.dylib, and the other that links with the newer libc++.dylib. libstdc++ is occasionally needed for some legacy applications, especially those that must run on OS X 10.6 Snow Leopard.
Going forward, we plan to stop providing the libstdc++-linked libLeap.dylib.
Apple changed Xcode to default to libc++ more than two years ago. When we removed support for OS X 10.6 for the Leap Motion Core Services, libstdc++ compatibility became less relevant. Most of the OS X C++ or Objective-C++ developers here are are likely already using libc++ anyway.
Those who aren't yet, you can configure this in Xcode with :
C++ Standard Library libc++ (LLVM C++ standard library with C++11 support)
The one remaining use-case for the libstdc++ version of libLeap.dylib would be if you have an application that is intended to be compatible with OS X 10.6, while the Leap features would only work on OS X 10.7 or higher. Google Earth was an example of such an app at one time. In this case, there are still workarounds such as using an older unsupported version of libLeap.dylib, or delay-loading the Leap library with dlopen().
Note that this only applies to OS X. On Linux, libstdc++ remains the C++ runtime library of choice.