From: usa@...
Date: 2016-04-22T09:42:26+00:00
Subject: [ruby-core:75120] [Ruby trunk Bug#12082] Tail-calling method can't catch exception raised by tail-called method

Issue #12082 has been updated by Usaku NAKAMURA.

Backport changed from 2.1: WONTFIX, 2.2: REQUIRED, 2.3: REQUIRED to 2.1: WONTFIX, 2.2: DONE, 2.3: REQUIRED

ruby_2_2 r54698 merged revision(s) 54542,54548.

----------------------------------------
Bug #12082: Tail-calling method can't catch exception raised by tail-called method
https://bugs.ruby-lang.org/issues/12082#change-58251

* Author: Kazuki Yamaguchi
* Status: Closed
* Priority: Normal
* Assignee: Koichi Sasada
* ruby -v: 
* Backport: 2.1: WONTFIX, 2.2: DONE, 2.3: REQUIRED
----------------------------------------
The following code doesn't work as expected, on all versions of Ruby with tail call optimization (1.9.1 to 2.3.0).

~~~ruby
def do_raise
  raise "should be rescued"
end
options = {
  tailcall_optimization: true,
  trace_instruction: false,
}
RubyVM::InstructionSequence.compile(<<EOF, __FILE__, __FILE__, __LINE__, options).eval
  def test_rescue
    return do_raise
    1 + 2
  rescue
    :ok
  end
EOF

p test_rescue # should print :ok, but raises "should be rescued"
~~~

Looks like `nop` instruction is (also) used to avoid this optimization ([compile.c](https://github.com/ruby/ruby/blob/1282a4a/compile.c#L4321)), but when doing early return, no `nop` is inserted.

I attached a (dirty) fix for this. Maybe there is a cleaner way.

---Files--------------------------------
0001-compile.c-don-t-do-tail-call-optimization-if-covered.patch (7.21 KB)
0001-compile.c-don-t-do-tail-call-optimization-if-covered-v2.patch (7.49 KB)


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