Facebook SDK is so buggy for iPhone. Started from the bug discussed here: Facebook iOS8 SDK build module error for FBSDKCoreKit Finally I solved it in an interesting way: the key was that I needed refer to the SDK where I installed it rather than copying the SDK into my app. Plus the FacebookAppID for every app should be unique, otherwise, the issues related to the linkers occur.
Anyway, when I run my FB app using XCode Simulator, I got the login page, and after it, I am directed to the window "You have already authorized MyAppName". The above button "Confirm" does not work at all, and, if I press another buttons like "OK" or "Cancel", I got the error: "Safari cannot open the page because the address is invalid". It looks that the address in the safari address field is like "https://m.facebook.com/v2.3/dialog/oauth/confirm"
My version of iOS: 8.1. XCode Version: 6.1. The app is simulated for iPhone 6.