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Created attachment 17660 [details]
Template Cycle 5 iPad project, for reference
"Stop Debugging" command causes iOS apps to crash with "Assertion at ... debugger-agent.c... condition `flags == 0' not met" rather than exiting gracefully
One ugly thing this does is fill up the device with crash logs during just any old start-and-stop debugging of an app.
Taking into consideration my observations on Bug 43929, I also have a hunch that this underlying issue might somehow account for a new cluster of bugs reported against Cycle 8: Bug 44567, Bug 44578, Bug 44301. My (wild) guess is that some timing or conditional logic might have changed in Cycle 8 in such a way that this failed assertion is now being triggered in certain environments at the _start_ of debugging rather than at the end of debugging.
## Regression status: The problem first appeared between Cycle 5 SR 5 and Cycle 6 SR 4
> BAD Cycle 8 + iOS 10.0.1 device. XamarinVS 18.104.22.1680 (c4382f5) + Xamarin.iOS 10.0.0.6 (6c3fee4) + Mono 4.6.0 (746756c) + Xcode 8.0, 8A218a
> BAD Cycle 8 + iOS 8.0 device. XamarinVS 22.214.171.1240 (c4382f5) + Xamarin.iOS 10.0.0.6 (6c3fee4) + Mono 4.6.0 (746756c) + Xcode 8.0, 8A218a
> BAD Cycle 7 + iOS 8.0 device. XamarinVS 126.96.36.1990 (2e39740) + Xamarin.iOS 188.8.131.523 (39ebb77) + Mono 4.4.0 (5995f74) + Xcode 7.3, 7D175
> BAD Cycle 6 SR 4 + iOS 8.0 device. XamarinVS 184.108.40.206 (a9c7826) + Xamarin.iOS 220.127.116.11 (d8bedd0) + Mono 4.2.4 (71b88f3) + Xcode 7.3, 7D175
> GOOD Cycle 5 SR 5 + iOS 8.0 device. XamarinVS 3.11.1594.0 (a06d6d5) + Xamarin.iOS 18.104.22.168 (1f068b4) + Mono 4.0.5 (1d8d582) + Xcode 7.3, 7D175
> GOOD Cycle 5 SR 5 + iOS 8.0 device. XamarinVS 3.11.1594.0 (a06d6d5) + Xamarin.iOS 22.214.171.124 (1f068b4) + Mono 4.0.5 (1d8d582) + Xcode 6.4, 6E35b
## Steps to replicate
1. Create a new "Visual C# > iOS > iPad > Single View App (iPad)" or "Visual C# > iOS > iPhone > Single View App (iPhone)" project. (I have also a attached a sample iPad project created using Cycle 5 SR 5 that I used for some of my tests.)
2. If needed for the current test device, edit the `Info.plist` to set the deployment target to 8.0 or lower.
3. Select "Debug > Start Debugging" to build and run the project on device in the "Debug|iPhone" configuration.
4. After the app launches successfully, select "Debug > Stop Debugging".
## BAD Results
The app exits due to a crash rather than exiting gracefully.
### The iOS device system log shows a failed assertion, followed by a stack trace, and then a message indicating that the app has crashed
> * Assertion at /Users/builder/data/lanes/3426/6c3fee4d/source/xamarin-macios/external/mono/mono/mini/debugger-agent.c:9864, condition `flags == 0' not met
> Application 'UIKitApplication:com.your-company.UnifiedSingleViewIpadC5[0x46e7]' crashed.
## GOOD Results (with Cycle 5 SR 5)
_When_ it stops the app successfully, C5SR5 produces a more graceful exit. The device logs show something "nice" like:
> Application 'UIKitApplication:com.your-company.UnifiedSingleViewIpad1[0xf3bb]' exited voluntarily.
But I should probably also note that the old build host in C5SR5 had issues with consistently quitting the app on every debugging attempt, so it did sometimes take me a couple redeploy attempts to get the IDE to close the app as expected with the "Stop Debugging" command.
## GOOD Results (with Cycle 8 Xamarin Studio 6.1 on Mac)
The device logs show the "nice" message as in C5SR5 XamarinVS:
> Application 'UIKitApplication:com.your-company.UnifiedSingleViewIpadC5[0x13e5]' exited
## Additional environment info
### Devices tested
iPhone 6s Plus, iOS 10.0.1 (14A403), English/USA locale
iPad Mini 2, iOS 8.0 (12A365), English/USA locale
Microsoft Visual Studio Professional 2015
Version 14.0.25431.01 Update 3
Windows 10 Version 10.0 (Build 10240), English/USA locale
OS X 10.11.6, English/USA locale
Created attachment 17661 [details]
IDE, build, and device logs and IDE version info
Fixed in version 126.96.36.199 (master)
Commit: bd6a3995f2c45e2efb71e064c351d43432c45c81 (xamarin/XamarinVS)
Fixed in version 188.8.131.520 (cycle9)
Commit: 9e2570764f745fd3ff85b5bd4bd104a35cfa7988 (xamarin/XamarinVS)