FBSDKLoginManager: undefined symbols for architecture x86_64 + linker command failed with exit code 1

I ran into the same problem. If you're adding Facebook Login to your app (which I presume you are) you also need to drag the FBSDKLoginKit.framework file into your Xcode project in addition to the FBSDKCoreKit.framework file.

The current instructions on Facebook's SDK Getting Started page forget to mention this. In version < 4 of the SDK, there was just one file to drag in to your project.