[ruby-core:84203] [Ruby trunk Feature#14143] Thread.report_on_exception should be true by default

Issue #14143 has been updated by Eregon (Benoit Daloze).


matz (Yukihiro Matsumoto) wrote:
> OK, it will be merged to 2.5RC1. If something (bad) happens, we will revert it.

Thank you!
I will provide a patch as soon as possible.

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Feature #14143: Thread.report_on_exception should be true by default
https://bugs.ruby-lang.org/issues/14143#change-68320

* Author: Eregon (Benoit Daloze)
* Status: Open
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
* Target version: 2.5
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Extracted from #6647 to focus on the default value now that the feature is implemented.

I strongly believe we should have Thread.report_on_exception = true by default.

It only adds some extra stderr output for apps which let threads die, which is very rarely intended.
If it is intended, then one can use Thread.current.report_on_exception = false
to clarify it's OK for that thread to die and the failure is handled by the app on Thread#join.

I enabled Thread.report_on_exception=true by default in ruby/spec, see https://github.com/ruby/spec/pull/517,
the only cases needing Thread.current.report_on_exception=false
are the specs testing report_on_exception itself and Thread#join/value/status/raise.

Enabling it for test-all shows a fair amount of extra output and failures, which I would bet some of them are bugs in the tests (I already found one, r60854 & r60870),
and other tests should simply more carefully test what they expect
(for instance assert_raise() inside the Thread just around the code raising an exception and join the Thread).

I am willing to help to reduce the extra output and failures in test-all,
but I would like a OK from Matz to try enabling Thread.report_on_exception by default.

Dear Matz, do you think it is reasonable to show exceptions killing threads on stderr by default,
instead of silently swallowing them until Thread#join ?
(if there is ever a Thread#join ..., often not or too late, when the rest of the application has crashed)



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