if you include VerifyStoreReceipt.h into an AppDelegate.mm the linking will fail with this message:
Undefined symbols for architecture armv7:
"verifyReceiptAtPath(NSString*)", referenced from:
-[AppDelegate validateReceipt:tryAgain:] in AppDelegate.o
ld: symbol(s) not found for architecture armv7
Other architectures fail also. This can easily be reproduced by changing the example projects appdelegates file extension from .m to .mm