From 3ee4fa9491d0b2b5fb40deea8e93e797924de789 Mon Sep 17 00:00:00 2001
From: "nicholas a. evans" <nicholas.evans@gmail.com>
Date: Sun, 21 Feb 2021 16:33:11 -0500
Subject: Send :fiber_switch event for almost every fiber_switch (#4207)

With this patch, TracePoint receives a `:fiber_switch` event for
_almost_ every fiber switch.  Previously, it would not be sent when an
exception was going to be raised. Now the event should only be blockable
by an interrupt (including `Thread#raise`) or a fatal error.

Additionally, interrupts will now be checked on the return fiber
_before_ re-raising the terminating unhandled exception.  And a fiber
that terminates with an unhandled exception no longer creates a pending
interrupt on its thread.  The exception will be raised in the return
fiber the same way as `Fiber#raise`: using `cont.value` with `cont.argc
== -1`

I moved `rb_exc_raise` from `fiber_store` to the end of `fiber_switch`
after _all_ of the other cleanup code: `fiber_stack_release`,
`th->blocking` increment, `RUBY_VM_CHECK_INTS`, and `EXEC_EVENT_HOOK`.
It seems to me that skipping those other cleanup steps may have also
resulted in other bugs.
---
 test/ruby/test_settracefunc.rb | 62 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)

(limited to 'test')

diff --git a/test/ruby/test_settracefunc.rb b/test/ruby/test_settracefunc.rb
index 1d16b2e154..fdd5bd2dce 100644
--- a/test/ruby/test_settracefunc.rb
+++ b/test/ruby/test_settracefunc.rb
@@ -1593,6 +1593,33 @@ class TestSetTraceFunc < Test::Unit::TestCase
       assert_equal ev, :fiber_switch
     }
 
+    # test for raise into resumable fiber
+    evs = []
+    f = nil
+    TracePoint.new(:raise, :fiber_switch){|tp|
+      next unless target_thread?
+      evs << [tp.event, Fiber.current]
+    }.enable{
+      f = Fiber.new{
+        Fiber.yield # will raise
+        Fiber.yield # unreachable
+      }
+      begin
+        f.resume
+        f.raise StopIteration
+      rescue StopIteration
+        evs << :rescued
+      end
+    }
+    assert_equal [:fiber_switch, f],             evs[0], "initial resume"
+    assert_equal [:fiber_switch, Fiber.current], evs[1], "Fiber.yield"
+    assert_equal [:fiber_switch, f],             evs[2], "fiber.raise"
+    assert_equal [:raise, f],                    evs[3], "fiber.raise"
+    assert_equal [:fiber_switch, Fiber.current], evs[4], "terminated with raise"
+    assert_equal [:raise, Fiber.current],        evs[5], "terminated with raise"
+    assert_equal :rescued,                       evs[6]
+    assert_equal 7, evs.size
+
     # test for transfer
     evs = []
     TracePoint.new(:fiber_switch){|tp|
@@ -1615,6 +1642,41 @@ class TestSetTraceFunc < Test::Unit::TestCase
     evs.each{|ev|
       assert_equal ev, :fiber_switch
     }
+
+    # test for raise and from transferring fibers
+    evs = []
+    f1 = f2 = nil
+    TracePoint.new(:raise, :fiber_switch){|tp|
+      next unless target_thread?
+      evs << [tp.event, Fiber.current]
+    }.enable{
+      f1 = Fiber.new{
+        f2.transfer
+        f2.raise ScriptError
+        Fiber.yield :ok
+      }
+      f2 = Fiber.new{
+        f1.transfer
+        f1.transfer
+      }
+      begin
+        f1.resume
+      rescue ScriptError
+        evs << :rescued
+      end
+    }
+    assert_equal [:fiber_switch, f1],            evs[0], "initial resume"
+    assert_equal [:fiber_switch, f2],            evs[1], "f2.transfer"
+    assert_equal [:fiber_switch, f1],            evs[2], "f1.transfer"
+    assert_equal [:fiber_switch, f2],            evs[3], "f2.raise ScriptError"
+    assert_equal [:raise,        f2],            evs[4], "f2.raise ScriptError"
+    assert_equal [:fiber_switch, f1],            evs[5], "f2 unhandled exception"
+    assert_equal [:raise,        f1],            evs[6], "f2 unhandled exception"
+    assert_equal [:fiber_switch, Fiber.current], evs[7], "f1 unhandled exception"
+    assert_equal [:raise,        Fiber.current], evs[8], "f1 unhandled exception"
+    assert_equal :rescued,                       evs[9], "rescued everything"
+    assert_equal 10, evs.size
+
   end
 
   def test_tracepoint_callee_id
-- 
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