Issue #11335 has been reported by Math Ieu.

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Bug #11335: `ruby -r debug` catchpoint problem
https://bugs.ruby-lang.org/issues/11335

* Author: Math Ieu
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: ruby 2.1.6p336 (2015-04-13 revision 50298) [i386-freebsd10]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
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With a `test-debug.rb` like this:

~~~
raise 'test'
~~~

And starting the debugger like this:

~~~
ruby -r debug test-debug.rb
~~~

By default, the catchpoint is `StandardError`, but it doesn't work:

~~~
test-debug.rb:1:raise 'test'
(rdb:1) catch
Catchpoint StandardError.
(rdb:1) c
test-debug.rb:1:in `<main>': test (RuntimeError)
~~~

And the debugger exits without catching the exception.

But, by setting the catchpoint to `NilClass` (or one of its ancestors), then it works:

~~~
test-debug.rb:1:raise "test"
(rdb:1) catch NilClass
Set catchpoint NilClass.
(rdb:1) c
test-debug.rb:1: `' (NilClass)
        from test-debug.rb:1:in `<main>'
test-debug.rb:1:raise "test"
~~~

And the debugger does not exit and allows further debugging.

By looking at `lib/debug.rb`, it looks like that the `set_trace_func` callback it sets assumes that `$!` will be set to the exception to be raised when a `'raise'` event occurs.  But it is not the case, `$!` seems to always be `nil`.




-- 
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