EXC_BAD_ACCESS

[dipyalov]

+ (void)initialize { if (self == [FBUnitySDKDelegate class]) { g_instances = [NSMutableArray array]; } }
in FBUnitySdkDelegate.m should be written as
+ (void)initialize { if (self == [FBUnitySDKDelegate class]) { g_instances = [[NSMutableArray alloc] init]; } }

because call to array autoreleases g_instances and makes app crash on complete call

[Decavoid]

Make sure you are compiling with ARC enabled.
http://clang.llvm.org/docs/AutomaticReferenceCounting.html#objects

If an object is declared with retainable object owner type, but without an explicit ownership qualifier, its type is implicitly adjusted to have __strong qualification.

[dipyalov]

Thank you! I've set -fobjc-arc on all .m/.mm files of the wrapper and it did help.