From: k@...
Date: 2016-03-09T09:24:20+00:00
Subject: [ruby-core:74240] [Ruby trunk Bug#12082] Tail-calling method can't catch exception raised by tail-called method

Issue #12082 has been updated by Kazuki Yamaguchi.

File 0001-compile.c-don-t-do-tail-call-optimization-if-covered-v2.patch added

Updating my patch, because it breaks such code:

~~~ruby
def errinfo
  $!
end
RubyVM::InstructionSequence.compile(<<EOF, __FILE__, __FILE__, __LINE__, tailcall_optimization: true).eval
  def test_rescue
    raise "a"
  rescue
    errinfo
  end
EOF

p test_rescue # should return a RuntimeError
~~~

----------------------------------------
Bug #12082: Tail-calling method can't catch exception raised by tail-called method
https://bugs.ruby-lang.org/issues/12082#change-57376

* Author: Kazuki Yamaguchi
* Status: Open
* Priority: Normal
* Assignee: Koichi Sasada
* ruby -v: 
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN
----------------------------------------
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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