it is all about silent crashes https://dkimitsa.github.io/2018/02/12/investigating-silent-crash/

I'm not sure why this is a fix.
Doesn't this only fix the symptoms and not the cause?
The cause being that system.err should flush on each and every print/write/append/whatever call?

Please correct me if I'm wrong :)

@intrigus hi :)
please check long read link in the comment above )

@dkimitsa I re-read your post, but I still think that the better solution would be to flush here:

instead of flushing in the uncaughtExceptionHandler.

OpenJDK does it the same way by printlning the information:
https://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/java/lang/Throwable.java#524

@intrigus flushing in Throwable. printStackTrace is not a good idea as these methods are public ones and available for usage widely in user code. Flushing there will be unexpected behavior.

Open JDK doesn't do it same way. It is just uses println. println doesn't mean it will flush.
Flush in println is specific implementation of FoundationLogPrintStream

Flush in uncaughtExceptionHandler is good idea as it is last resort of application running code. And if flush is not happened any other place it is good place to do it before crashing