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


@shevegen (Robert A. Heiler) wrote:
> So to me, that first initial step, to find out how to deal with
> threads in Ruby, was not trivial to find out. In that context
> I agree with Benoit's comment "Nobody should have to remember"
> which I think is a fine statement, in particular by people who
> are new to ruby. It's not so difficult for more experienced,
> older ruby people but for newcomers, making threads as simple
> as possible would be good, IMO.

I think it is also a problem even for experienced rubyists.
I often forget to add Thread.{report or abort}_on_exception = true.
It is not easy to remember that every Thread.new{} has to use these extra lines at the beginning
or threads might crash silently with no easy way to debug.

@headius was saying on IRC #jruby yesterday that he experiences this problem at least once a month.
@enebo was talking about a similar scenario than yours:
GUI programming with threads in Ruby is harder than it should because errors go unnoticed.

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Feature #14143: Thread.report_on_exception should be true by default
https://bugs.ruby-lang.org/issues/14143#change-68081

* Author: Eregon (Benoit Daloze)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
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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