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Hi, My name is Michael Williams from Microsoft, I am the Xamarin TSP based in APAC. A customer in Australia has found an issue within the Xamarin.iOS library calling the following line: UIKit.UIAccessibility.RequestGuidedAccessSession(true, (obj) => { }); They are trying to use the app in Kiosk mode using guided access. Produces the following stack trace: 2017-09-03 16:50:24.649 MVVMArchitecture.iOS[34054:791525] critical: Stacktrace: 2017-09-03 16:50:24.649 MVVMArchitecture.iOS[34054:791525] critical: at <unknown> <0xffffffff> 2017-09-03 16:50:24.650 MVVMArchitecture.iOS[34054:791525] critical: at (wrapper managed-to-native) UIKit.UIAccessibility.UIAccessibilityRequestGuidedAccessSession (bool,System.Action`1<bool>) [0x0001c] in <ef46365b0eaf490385df9fbc37d3de31>:0 2017-09-03 16:50:24.651 MVVMArchitecture.iOS[34054:791525] critical: at UIKit.UIAccessibility.RequestGuidedAccessSession (bool,System.Action`1<bool>) [0x0001c] in /Users/builder/data/lanes/4991/80b8487d/source/xamarin-macios/src/UIKit/UIAccessibility.cs:209 2017-09-03 16:50:24.651 MVVMArchitecture.iOS[34054:791525] critical: at MVVMArchitecture.iOS.AppDelegate.FinishedLaunching (UIKit.UIApplication,Foundation.NSDictionary) [0x00013] in /Users/mww121/Projects/MVVMArchitecture/iOS/AppDelegate.cs:18 2017-09-03 16:50:24.651 MVVMArchitecture.iOS[34054:791525] critical: at (wrapper runtime-invoke) <Module>.runtime_invoke_bool__this___object_object (object,intptr,intptr,intptr) [0x00063] in <20bae823e3b64327a3b6e9bb4565cd6a>:0 2017-09-03 16:50:24.651 MVVMArchitecture.iOS[34054:791525] critical: at <unknown> <0xffffffff> 2017-09-03 16:50:24.652 MVVMArchitecture.iOS[34054:791525] critical: at (wrapper managed-to-native) UIKit.UIApplication.UIApplicationMain (int,string[],intptr,intptr) [0x0005c] in <ef46365b0eaf490385df9fbc37d3de31>:0 2017-09-03 16:50:24.652 MVVMArchitecture.iOS[34054:791525] critical: at UIKit.UIApplication.Main (string[],intptr,intptr) [0x00005] in /Users/builder/data/lanes/4991/80b8487d/source/xamarin-macios/src/UIKit/UIApplication.cs:79 2017-09-03 16:50:24.652 MVVMArchitecture.iOS[34054:791525] critical: at UIKit.UIApplication.Main (string[],string,string) [0x00038] in /Users/builder/data/lanes/4991/80b8487d/source/xamarin-macios/src/UIKit/UIApplication.cs:63 2017-09-03 16:50:24.652 MVVMArchitecture.iOS[34054:791525] critical: at MVVMArchitecture.iOS.Application.Main (string[]) [0x00001] in /Users/mww121/Projects/MVVMArchitecture/iOS/Main.cs:17 2017-09-03 16:50:24.652 MVVMArchitecture.iOS[34054:791525] critical: at (wrapper runtime-invoke) <Module>.runtime_invoke_void_object (object,intptr,intptr,intptr) [0x00051] in <20bae823e3b64327a3b6e9bb4565cd6a>:0 2017-09-03 16:50:24.652 MVVMArchitecture.iOS[34054:791525] critical: Native stacktrace: 2017-09-03 16:50:24.684 MVVMArchitecture.iOS[34054:791525] critical: 0 MVVMArchitecture.iOS 0x000000010fbd31e4 mono_handle_native_crash + 244 2017-09-03 16:50:24.685 MVVMArchitecture.iOS[34054:791525] critical: 1 MVVMArchitecture.iOS 0x000000010fbe0a70 mono_sigsegv_signal_handler + 288 2017-09-03 16:50:24.685 MVVMArchitecture.iOS[34054:791525] critical: 2 libsystem_platform.dylib 0x000000011b9d6b3a _sigtramp + 26 2017-09-03 16:50:24.685 MVVMArchitecture.iOS[34054:791525] critical: 3 libsystem_malloc.dylib 0x000000011b7a5c88 _nano_malloc_check_clear + 583 2017-09-03 16:50:24.685 MVVMArchitecture.iOS[34054:791525] critical: 4 libsystem_blocks.dylib 0x000000011b60fb20 _Block_object_assign + 98 2017-09-03 16:50:24.685 MVVMArchitecture.iOS[34054:791525] critical: 5 libsystem_blocks.dylib 0x000000011b60f8f0 _Block_copy + 113 2017-09-03 16:50:24.685 MVVMArchitecture.iOS[34054:791525] critical: 6 libdispatch.dylib 0x000000011b55d56d _dispatch_Block_copy + 43 2017-09-03 16:50:24.685 MVVMArchitecture.iOS[34054:791525] critical: 7 libdispatch.dylib 0x000000011b562dfe dispatch_async + 67 2017-09-03 16:50:24.686 MVVMArchitecture.iOS[34054:791525] critical: 8 UIKit 0x0000000114265145 +[NSObject(UIAccessibilityPrivate) __accessibilityRequestGuidedAccessSession:completion:] + 79 2017-09-03 16:50:24.686 MVVMArchitecture.iOS[34054:791525] critical: 9 ??? 0x00000001341c66b7 0x0 + 5169243831 2017-09-03 16:50:24.686 MVVMArchitecture.iOS[34054:791525] critical:
Please include your full build logs, crash reports (if any), test case (to reproduce) and all version information. To get full build logs just set the log verbosity to diagnostic at the following locations: - On Visual Studio for Mac: Preferences > Projects > Build - On Visual Studio for Windows: Tools > Options > Projects and Solutions > Build and Run On Visual Studio Windows you also want to add `-v -v -v -v` to the mtouch additional arguments by right-clicking the project in the solution explorer and selecting `Properties`. Note: this is done automatically on Visual Studio for Mac when the log verbosity is set to diagnostic. Easiest way to get exact version information: - On Visual Studio for Mac: "Visual Studio" menu, "About Visual Studio" item, "Show Details" button. - On Visual Studio for Windows: "Help menu", "About Microsoft Visual Studio" item. Then copy/paste the version information (you can use the "Copy Information" button). Once we have the information we will try to reproduce the issue an investigate further.
This is because the native method is bound (using a P/Invoke) as if the callback was a C method, and not an Objective-C block: https://github.com/xamarin/xamarin-macios/blob/8178ecc5eaa6f7a43f7bf53d5aec44461ffe5cb8/src/UIKit/UIAccessibility.cs#L200
Looks like we wrote a test when it was implemented, but it's commented out: https://github.com/xamarin/xamarin-macios/blob/8178ecc5eaa6f7a43f7bf53d5aec44461ffe5cb8/tests/monotouch-test/UIKit/AccessibilityTest.cs#L37
Let's try to get this fixed in 15.5.
PR https://github.com/xamarin/xamarin-macios/pull/2917
PR merged in master with https://github.com/xamarin/xamarin-macios/commit/584da1da18793cb6c5fc49ecc39dadcbedb591c5