From: "Iñaki Baz Castillo" <ibc@...>
Date: 2008-07-21T03:18:24+09:00
Subject: Why Thread.abort_on_exception = yes doesn't show errors?

Hi, when Thread.abort_on_exception = yes I don't see any error log in the 
screen. Note those cases:


case 1) It's seems correct:
---------------------
t = Thread.new {
        sleep 1
        qwe
}
t.abort_on_exception = true

puts "hello !!!"
sleep 2
puts "END"
---------------------
=>
hello !!!
test.rb:3: undefined local variable or method `qwe' for main:Object 
(NameError)
        from test.rb:1:in `initialize'
        from test.rb:1:in `new'
        from test.rb:1



case 2) Why the error is not shown???
---------------------
t = Thread.new {
        sleep 1
        qwe
}
t.abort_on_exception = false

puts "hello !!!"
sleep 2
puts "END"
---------------------
=>  
hello !!!
END



case 3) But if I do a t.join then the error is shown and the program 
exists !!!:
---------------------
t = Thread.new {
        sleep 1
        qwe
}
t.abort_on_exception = false

puts "hello !!!"
t.join
puts "END"
---------------------
=>  
hello !!!
test.rb:3: undefined local variable or method `qwe' for main:Object 
(NameError)
        from test.rb:8:in `join'
        from test.rb:8



Conclusion:

- If a thread is joined then if that threads has a non handled exception the 
program will exit (except if the main program handles that exception).

- If a thread is "abort_on_exception = true" then the program will fail in the 
moment the thread fails (it makes sense).

- If a thead is "abort_on_exception = false" then nothing will occur if the 
threads fails, and no error output will occur. WHY ???


Any comment is appreciated.

-- 
Iñaki Baz Castillo