I'm encountering a difficult to debug issue with a static library project when attempting to animate a view. It works fine when debugging (and even when debugging in the release configuration), but throws an error archived as a release: Exception Type: EXC_CRASH (SIGSYS) Exception Codes: 0x00000000, 0x00000000 Crashed Thread: 0 Thread 0 name: Dispatch queue: com.apple.main-thread Thread 0 Crashed: 0 TestApp 0x000d04fc 0x91000 + 259324 1 UIKit 0x336d777e +[UIView(UIViewAnimationWithBlocks) animateWithDuration:animations:] + 42 2 TestApp 0x000d04de 0x91000 + 259294 3 TestApp 0x000d0678 0x91000 + 259704 4 Foundation 0x355f04f8 __57-[NSNotificationCenter addObserver:selector:name:object:]_block_invoke_0 + 12 5 CoreFoundation 0x35aae540 ___CFXNotificationPost_block_invoke_0 + 64 6 CoreFoundation 0x35a3a090 _CFXNotificationPost + 1400 7 Foundation 0x355643e4 -[NSNotificationCenter postNotificationName:object:userInfo:] + 60 8 UIKit 0x33599112 -[UIInputViewTransition postNotificationsForTransitionStart] + 846 9 UIKit 0x335988cc -[UIPeripheralHost(UIKitInternal) executeTransition:] + 880 10 UIKit 0x3351bb8c -[UIPeripheralHost(UIKitInternal) setInputViews:animationStyle:] + 304 11 UIKit 0x3351b260 -[UIPeripheralHost(UIKitInternal) _reloadInputViewsForResponder:] + 952 12 UIKit 0x3351ae54 -[UIResponder(UIResponderInputViewAdditions) reloadInputViews] + 160 13 UIKit 0x3351a990 -[UIResponder becomeFirstResponder] + 452 14 UIKit 0x336194a0 -[UITextInteractionAssistant setFirstResponderIfNecessary] + 168 15 UIKit 0x33618d6a -[UITextInteractionAssistant oneFingerTap:] + 1602 16 UIKit 0x33618630 _UIGestureRecognizerSendActions + 100 17 UIKit 0x335a8d5e -[UIGestureRecognizer _updateGestureWithEvent:] + 298 18 UIKit 0x337d9472 ___UIGestureRecognizerUpdate_block_invoke_0541 + 42 19 UIKit 0x33524f4e _UIGestureRecognizerApplyBlocksToArray + 170 20 UIKit 0x33523a9c _UIGestureRecognizerUpdate + 892 21 UIKit 0x335307e2 _UIGestureRecognizerUpdateGesturesFromSendEvent + 22 22 UIKit 0x33530620 -[UIWindow _sendGesturesForEvent:] + 768 23 UIKit 0x335301ee -[UIWindow sendEvent:] + 82 24 UIKit 0x3351668e -[UIApplication sendEvent:] + 350 25 UIKit 0x33515f34 _UIApplicationHandleEvent + 5820 26 GraphicsServices 0x376d5224 PurpleEventCallback + 876 27 CoreFoundation 0x35ab651c __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 32 28 CoreFoundation 0x35ab64be __CFRunLoopDoSource1 + 134 29 CoreFoundation 0x35ab530c __CFRunLoopRun + 1364 30 CoreFoundation 0x35a3849e CFRunLoopRunSpecific + 294 31 CoreFoundation 0x35a38366 CFRunLoopRunInMode + 98 32 GraphicsServices 0x376d4432 GSEventRunModal + 130 33 UIKit 0x33544cce UIApplicationMain + 1074 Thread 0 crashed with ARM Thread State: r0: 0x0000004e r1: 0x000d04f8 r2: 0x338fed47 r3: 0x3f523340 r4: 0x00000000 r5: 0x2fe8da00 r6: 0x00000001 r7: 0x2fe8d9d0 r8: 0x3f54cad0 r9: 0x00000000 r10: 0x3fd00000 r11: 0x3f523310 ip: 0x3f497048 sp: 0x2fe8d988 lr: 0x33539a41 pc: 0x000d04fc cpsr: 0x60000010 To give some background info: The static library is part of an 'iOS fake-framework', built using the templates from here: https://github.com/kstenerud/iOS-Universal-Framework The framework presents a registration UI as a modal view on top of whatever the client application is doing at the time. It pushes these views using a handle to a UIViewController provided by the client application. It doesn't do anything special, but here's the animation code: -(void)keyboardWillShowNotification:(NSNotification *)notification { double animationDuration = [[[notification userInfo] objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue]; dispatch_async(dispatch_get_main_queue(), ^(void) { [self animateViewsToState:kUMAnimationStateKeyboardVisible forIdiom:[UIDevice currentDevice].userInterfaceIdiom forDuration:animationDuration]; }); } -(void)animateViewsToState:(kUMAnimationState)state forIdiom:(UIUserInterfaceIdiom)idiom forDuration:(double)duration { float fieldOffset; if (idiom == UIUserInterfaceIdiomPhone) { if (state == kUMAnimationStateKeyboardVisible) { fieldOffset = -KEYBOARD_HEIGHT_IPHONE_PORTRAIT; } else { fieldOffset = KEYBOARD_HEIGHT_IPHONE_PORTRAIT; } } else { if (state == kUMAnimationStateKeyboardVisible) { fieldOffset = -IPAD_FIELD_OFFSET; } else { fieldOffset = IPAD_FIELD_OFFSET; } } [UIView animateWithDuration:duration animations:^(void) { mUserNameField.frame = CGRectOffset(mUserNameField.frame, 0, fieldOffset); mUserPasswordField.frame = CGRectOffset(mUserPasswordField.frame, 0, fieldOffset); }]; } Further printf-style debugging shows that it crashes whenever I do anything much with UIKit - specifically, it crashes when I replace -animateViewsToState with: if (0 == UIUserInterfaceIdiomPhone) { NSLog(@""); } and [[[[UIAlertView alloc] initWithTitle:@"test" message:@"123" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil] autorelease] show]; To me, this sounds like a linker problem, but I don't understand how such problems would only manifest here, and not beforehand. Any help would be greatly appreciated.