iOS crash when built with one version of Xcode, no crash with another version

I need to debug a crash that happens at a fundamental part of the app experience on a particular iOS version, but when I use the (newer)开发者_StackOverflow社区 dev tools for that version, the crash does not occur.

How can I get a GDB session on version of an app that was installed with another SDK version?

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See if you can build the app in Xcode 4.1 and deploy it to an iOS 5.0 device via TestFlight: https://testflightapp.com/