objective c - Xcode 7 warnings: object file was built for newer iOS version than being linked

Question

I recently integrated Google Cloud Messaging into an app targeting iOS 7 and iOS 8. Just grabbed Xcode 7 beta 4 to get started on iOS 9 support, and now I'm getting an error from the linker:

ld: warning: object file (.../Pods/GoogleInterchangeUtilities/Libraries
/libProtocolBuffers.a(Descriptor.pb.o)) was built for newer iOS version (8.3)
than being linked (7.0)

and a handful more like that all for parts of libProtocolBuffers.a.

Does this mean that iOS 8.3 is required to use the GCM library? If so, why did Xcode 6 happily spit out code that (by all appearances in my testing with iOS 7 devices) delivered push notifications to iOS 7.3 without issue?

Given that they're just warnings, I can still compile fine, however I prefer not to ship code that is wrong.

Edit: I emailed google and they said top people will look into it. In the mean time, if you're reading this and bothered by the warning, maybe also email so they'll be encouraged to deal with it.

Answer 1

It actually means that the Minimum Deployment Target of the included library was is to 8.3 and linking it with lower Minimum Deployment Target produces this warning.

Library does not officially support targets lower than 8.3 in this case. While linking this library to target with ower Minimum Deployment Target will still work, it might produce crashes at runtime, if any 8.3 only code is executed on a device that runs older system than 8.3.

There is a reason why developers set 8.3 as the minimum target and this warning should NOT be ignored. It might be harmless in this case, but it is not necessarily harmless in other cases!

To fix these warnings, either use an older version of the library or set your Minimum deployment target to 8.3.