iOS 10 App if we re in the real pre-commit handler we can t actually add any new fences due to CA restriction

Question

I sometimes get this message in the logs of Xcode 8b3 when running my app  everything seems to work  but I d like to know where this comes from  Google did not help at all

User · Answer

It comes from   UIWindow  synchronizeDrawingAcrossProcessesOverPort withPreCommitHandler   via os log API  It doesn t depend from another components frameworks that you are using only from UIKit  - it reproduces in clean single view application project on changing interface orientation   This method consists from 2 parts    adding passed precommit handler to list of handlers  do some work  that depends on current finite state machine state    When second part fails  looks like prohibited transition   it prints message above to error log  However  I think that this problem is not fatal  there are 2 additional assert cases in this method  that will lead to crash in debug   Seems that radar is the best we can do

User · Answer

in your Xcode    Click on your active scheme name right next to the Stop button Click on Edit Scheme     in Run  Debug  select the Arguments tab in Environment Variables click   add variable  OS ACTIVITY MODE   disable

User · Answer

We can mute it in this way  device and simulator need different values    Add the Name OS ACTIVITY MODE and the Value   DEBUG ACTIVITY MODE  and check it  in Product -  Scheme -  Edit Scheme -  Run -  Arguments -  Environment      Add User-Defined Setting DEBUG ACTIVITY MODE  then add Any iOS Simulator SDK for Debug and set it s value to disable  in Project -  Build settings -    -  User-Defined Setting

User · Answer

To fix  I deleted the app from Simulator   I also ran Clean first   I do not think anything orientation-related triggered it  The biggest thing that changed before this symptom started is that a Swift framework started calling NSLog on worker threads instead of main thread

User · Answer

OS ACTIVITY MODE   disable   This will also disable the ability to debug in real devices  no console output from real devices from then on

User · Answer

Try putting the following in the environment variables for the scheme under run debug   OS ACTIVITY MODE   disable

[ios] iOS 10: "[App] if we're in the real pre-commit handler we can't actually add any new fences due to CA restriction"

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