From 7dc850b64060de12f191b5df4a78d1c525a6f31c Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Mon, 24 Mar 2025 23:49:31 +0000
Subject: [PATCH 01/41] =?UTF-8?q?`test=5Fconcurrent=5Ffutures.test=5Fmap?=
 =?UTF-8?q?=5Fexception`:=20assert=20no=20reference=20cycle=20from=20faile?=
 =?UTF-8?q?d=20future=20captured=20in=20its=20exception=E2=80=99s=20traceb?=
 =?UTF-8?q?ack?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 Lib/test/test_concurrent_futures/executor.py | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index d88c34d1c8c8e4..375bae8be300f9 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -1,3 +1,4 @@
+import gc
 import itertools
 import threading
 import time
@@ -55,8 +56,20 @@ def test_map_exception(self):
         i = self.executor.map(divmod, [1, 1, 1, 1], [2, 3, 0, 5])
         self.assertEqual(i.__next__(), (0, 1))
         self.assertEqual(i.__next__(), (0, 1))
-        with self.assertRaises(ZeroDivisionError):
-            i.__next__()
+
+        error = None
+        try:
+            next(i)
+        except ZeroDivisionError as zero_div_error:
+            error = zero_div_error
+        self.assertIsNotNone(
+            error,
+            msg="next one should raise a ZeroDivisionError",
+        )
+
+        # a failed future must not be captured in its
+        # future._exception.__traceback__ to avoid a reference cycle
+        self.assertFalse(gc.get_referrers(error))
 
     @support.requires_resource('walltime')
     def test_map_timeout(self):

From 19edcedcf76f0ffbd13e19ffc00cf5e9f3b6bcbe Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Tue, 25 Mar 2025 00:33:59 +0000
Subject: [PATCH 02/41] test there is no future in referrers

---
 Lib/test/test_concurrent_futures/executor.py | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 375bae8be300f9..5496ba88475562 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -69,7 +69,12 @@ def test_map_exception(self):
 
         # a failed future must not be captured in its
         # future._exception.__traceback__ to avoid a reference cycle
-        self.assertFalse(gc.get_referrers(error))
+        self.assertFalse(
+            any(
+                isinstance(referrer, futures.Future)
+                for referrer in gc.get_referrers(error)
+            )
+        )
 
     @support.requires_resource('walltime')
     def test_map_timeout(self):

From 1c3d01ac1b696044b16e60e5c18f83a842d8f370 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Tue, 25 Mar 2025 01:42:12 +0000
Subject: [PATCH 03/41] switch to assertTrue(all(...))

---
 Lib/test/test_concurrent_futures/executor.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 5496ba88475562..9d4e687574eb4a 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -69,9 +69,9 @@ def test_map_exception(self):
 
         # a failed future must not be captured in its
         # future._exception.__traceback__ to avoid a reference cycle
-        self.assertFalse(
-            any(
-                isinstance(referrer, futures.Future)
+        self.assertTrue(
+            all(
+                not isinstance(referrer, futures.Future)
                 for referrer in gc.get_referrers(error)
             )
         )

From fa790f1329dc7359b8acfd35074339eb9ae40836 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Tue, 25 Mar 2025 11:12:36 +0000
Subject: [PATCH 04/41] add test msg

---
 Lib/test/test_concurrent_futures/executor.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 9d4e687574eb4a..d7c14aff9e3fbb 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -73,7 +73,8 @@ def test_map_exception(self):
             all(
                 not isinstance(referrer, futures.Future)
                 for referrer in gc.get_referrers(error)
-            )
+            ),
+            msg="none of the referrers should be a Future.",
         )
 
     @support.requires_resource('walltime')

From e48d0e01a24a91e1730093fb54af1270893b0466 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Tue, 25 Mar 2025 11:14:03 +0000
Subject: [PATCH 05/41] format msgs

---
 Lib/test/test_concurrent_futures/executor.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index d7c14aff9e3fbb..dde6f43b7acc59 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -74,7 +74,7 @@ def test_map_exception(self):
                 not isinstance(referrer, futures.Future)
                 for referrer in gc.get_referrers(error)
             ),
-            msg="none of the referrers should be a Future.",
+            msg="none of the referrers should be a Future",
         )
 
     @support.requires_resource('walltime')
@@ -159,7 +159,7 @@ def test_map_buffersize_when_buffer_is_full(self):
         self.assertEqual(
             next(ints),
             buffersize,
-            msg="should have fetched only `buffersize` elements from `ints`.",
+            msg="should have fetched only `buffersize` elements from `ints`",
         )
 
     def test_shutdown_race_issue12456(self):

From 99850b8c9531cbedc47263a7a05c41d349633ac8 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Tue, 25 Mar 2025 11:23:58 +0000
Subject: [PATCH 06/41] switch to assert list empty for a better assertion
 error message

---
 Lib/test/test_concurrent_futures/executor.py | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index dde6f43b7acc59..b939ef0379c375 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -69,11 +69,12 @@ def test_map_exception(self):
 
         # a failed future must not be captured in its
         # future._exception.__traceback__ to avoid a reference cycle
-        self.assertTrue(
-            all(
-                not isinstance(referrer, futures.Future)
+        self.assertFalse(
+            [
+                referrer
                 for referrer in gc.get_referrers(error)
-            ),
+                if isinstance(referrer, futures.Future)
+            ],
             msg="none of the referrers should be a Future",
         )
 

From 6e780140026081a4dff5bc4588b26502b1613742 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Wed, 26 Mar 2025 22:49:32 +0000
Subject: [PATCH 07/41] edit comment

---
 Lib/test/test_concurrent_futures/executor.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index b939ef0379c375..068c7aa494de95 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -67,7 +67,7 @@ def test_map_exception(self):
             msg="next one should raise a ZeroDivisionError",
         )
 
-        # a failed future must not be captured in its
+        # a failed future should not be captured in its
         # future._exception.__traceback__ to avoid a reference cycle
         self.assertFalse(
             [

From 3dc24610854ace9c177bfb9747f5c23ec80f0046 Mon Sep 17 00:00:00 2001
From: Thomas Grainger <tagrain@gmail.com>
Date: Sun, 30 Mar 2025 13:48:04 +0100
Subject: [PATCH 08/41] assert there are no reference cycles at all

---
 Lib/test/test_concurrent_futures/executor.py | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 068c7aa494de95..a52da877da21ef 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -69,14 +69,7 @@ def test_map_exception(self):
 
         # a failed future should not be captured in its
         # future._exception.__traceback__ to avoid a reference cycle
-        self.assertFalse(
-            [
-                referrer
-                for referrer in gc.get_referrers(error)
-                if isinstance(referrer, futures.Future)
-            ],
-            msg="none of the referrers should be a Future",
-        )
+        self.assertListEqual(gc.get_referrers(error), [])
 
     @support.requires_resource('walltime')
     def test_map_timeout(self):

From 4dce280760eb7d8d6b3d6cd3e69437774129ca54 Mon Sep 17 00:00:00 2001
From: Thomas Grainger <tagrain@gmail.com>
Date: Sun, 30 Mar 2025 13:48:38 +0100
Subject: [PATCH 09/41] avoid a reference cycle in subinterpreter pools

---
 Lib/concurrent/futures/interpreter.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/Lib/concurrent/futures/interpreter.py b/Lib/concurrent/futures/interpreter.py
index d17688dc9d7346..744ccafa012aa3 100644
--- a/Lib/concurrent/futures/interpreter.py
+++ b/Lib/concurrent/futures/interpreter.py
@@ -205,8 +205,7 @@ def run(self, task):
             assert res is None, res
             assert pickled
             assert exc_wrapper is not None
-            exc = pickle.loads(excdata)
-            raise exc from exc_wrapper
+            raise pickle.loads(excdata) from exc_wrapper
         return pickle.loads(res) if pickled else res
 
 

From 9bc69b9e90aa95395ba159579c21857712acdf96 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Sun, 30 Mar 2025 21:20:37 +0100
Subject: [PATCH 10/41] test that traceback frames should not contain any
 variables referring to an Exception or a failed Future

---
 Lib/test/test_concurrent_futures/executor.py | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index a52da877da21ef..7c6992a5ce356d 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -67,9 +67,22 @@ def test_map_exception(self):
             msg="next one should raise a ZeroDivisionError",
         )
 
-        # a failed future should not be captured in its
-        # future._exception.__traceback__ to avoid a reference cycle
-        self.assertListEqual(gc.get_referrers(error), [])
+        self.assertFalse(
+            gc.get_referrers(error),
+            msg="the raised error should not have any referrer",
+        )
+
+        tb = error.__traceback__
+        while (tb := tb.tb_next):
+            self.assertFalse(
+                {
+                    var: val
+                    for var, val in tb.tb_frame.f_locals.items()
+                    if isinstance(val, Exception)
+                    or (isinstance(val, futures.Future) and val.exception())
+                },
+                msg=f"traceback frames should not contain any variables referring to an Exception or a failed Future",
+            )
 
     @support.requires_resource('walltime')
     def test_map_timeout(self):

From 9c781c1a4ed3ced35b0fbd3c890a9e47812a76b0 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Sun, 30 Mar 2025 21:29:05 +0100
Subject: [PATCH 11/41] interpreter.WorkerContext.run: finally unassign
 exc_wrapper

---
 Lib/concurrent/futures/interpreter.py | 55 ++++++++++++++-------------
 1 file changed, 29 insertions(+), 26 deletions(-)

diff --git a/Lib/concurrent/futures/interpreter.py b/Lib/concurrent/futures/interpreter.py
index 744ccafa012aa3..758ce7a738bd15 100644
--- a/Lib/concurrent/futures/interpreter.py
+++ b/Lib/concurrent/futures/interpreter.py
@@ -179,34 +179,37 @@ def run(self, task):
             raise NotImplementedError(kind)
 
         try:
-            self._exec(script)
-        except ExecutionFailed as exc:
-            exc_wrapper = exc
-        else:
-            exc_wrapper = None
-
-        # Return the result, or raise the exception.
-        while True:
             try:
-                obj = _interpqueues.get(self.resultsid)
-            except _interpqueues.QueueNotFoundError:
-                raise  # re-raise
-            except _interpqueues.QueueError:
-                continue
-            except ModuleNotFoundError:
-                # interpreters.queues doesn't exist, which means
-                # QueueEmpty doesn't.  Act as though it does.
-                continue
+                self._exec(script)
+            except ExecutionFailed as exc:
+                exc_wrapper = exc
             else:
-                break
-        (res, excdata), pickled, unboundop = obj
-        assert unboundop is None, unboundop
-        if excdata is not None:
-            assert res is None, res
-            assert pickled
-            assert exc_wrapper is not None
-            raise pickle.loads(excdata) from exc_wrapper
-        return pickle.loads(res) if pickled else res
+                exc_wrapper = None
+
+            # Return the result, or raise the exception.
+            while True:
+                try:
+                    obj = _interpqueues.get(self.resultsid)
+                except _interpqueues.QueueNotFoundError:
+                    raise  # re-raise
+                except _interpqueues.QueueError:
+                    continue
+                except ModuleNotFoundError:
+                    # interpreters.queues doesn't exist, which means
+                    # QueueEmpty doesn't.  Act as though it does.
+                    continue
+                else:
+                    break
+            (res, excdata), pickled, unboundop = obj
+            assert unboundop is None, unboundop
+            if excdata is not None:
+                assert res is None, res
+                assert pickled
+                assert exc_wrapper is not None
+                raise pickle.loads(excdata) from exc_wrapper
+            return pickle.loads(res) if pickled else res
+        finally:
+            exc_wrapper = None
 
 
 class BrokenInterpreterPool(_thread.BrokenThreadPool):

From a438301404ac092e83c8a46fad7bbd5e364b5b84 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Sun, 30 Mar 2025 21:31:30 +0100
Subject: [PATCH 12/41] fix msg grammar

---
 Lib/test/test_concurrent_futures/executor.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 7c6992a5ce356d..35ab185f87ec78 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -69,7 +69,7 @@ def test_map_exception(self):
 
         self.assertFalse(
             gc.get_referrers(error),
-            msg="the raised error should not have any referrer",
+            msg="the raised error should not have any referrers",
         )
 
         tb = error.__traceback__

From ada614007556c13284dd2a81ac4cbbb0dacdb462 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Sun, 30 Mar 2025 21:47:00 +0100
Subject: [PATCH 13/41] fix access to exception

---
 Lib/test/test_concurrent_futures/executor.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 35ab185f87ec78..9349ac376a4c26 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -79,7 +79,7 @@ def test_map_exception(self):
                     var: val
                     for var, val in tb.tb_frame.f_locals.items()
                     if isinstance(val, Exception)
-                    or (isinstance(val, futures.Future) and val.exception())
+                    or (isinstance(val, futures.Future) and val._exception)
                 },
                 msg=f"traceback frames should not contain any variables referring to an Exception or a failed Future",
             )

From d5e8c7a40e0577aefd248471c4648320442fb2c5 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Sun, 30 Mar 2025 22:34:57 +0100
Subject: [PATCH 14/41] narrow test: traceback frames should not contain any
 exception

---
 Lib/test/test_concurrent_futures/executor.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 9349ac376a4c26..ac4d5aaa4434c6 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -79,9 +79,8 @@ def test_map_exception(self):
                     var: val
                     for var, val in tb.tb_frame.f_locals.items()
                     if isinstance(val, Exception)
-                    or (isinstance(val, futures.Future) and val._exception)
                 },
-                msg=f"traceback frames should not contain any variables referring to an Exception or a failed Future",
+                msg=f"traceback frames should not contain any exception",
             )
 
     @support.requires_resource('walltime')

From c4b771a19bed925aa6e586073be7a5de04b5eb1f Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Mon, 31 Mar 2025 10:51:56 +0100
Subject: [PATCH 15/41] clean up exc_wrapper with minimal indentation

---
 Lib/concurrent/futures/interpreter.py | 56 +++++++++++++--------------
 1 file changed, 28 insertions(+), 28 deletions(-)

diff --git a/Lib/concurrent/futures/interpreter.py b/Lib/concurrent/futures/interpreter.py
index 758ce7a738bd15..1c1187272a26ed 100644
--- a/Lib/concurrent/futures/interpreter.py
+++ b/Lib/concurrent/futures/interpreter.py
@@ -179,37 +179,37 @@ def run(self, task):
             raise NotImplementedError(kind)
 
         try:
+            self._exec(script)
+        except ExecutionFailed as exc:
+            exc_wrapper = exc
+        else:
+            exc_wrapper = None
+
+        # Return the result, or raise the exception.
+        while True:
             try:
-                self._exec(script)
-            except ExecutionFailed as exc:
-                exc_wrapper = exc
+                obj = _interpqueues.get(self.resultsid)
+            except _interpqueues.QueueNotFoundError:
+                raise  # re-raise
+            except _interpqueues.QueueError:
+                continue
+            except ModuleNotFoundError:
+                # interpreters.queues doesn't exist, which means
+                # QueueEmpty doesn't.  Act as though it does.
+                continue
             else:
-                exc_wrapper = None
-
-            # Return the result, or raise the exception.
-            while True:
-                try:
-                    obj = _interpqueues.get(self.resultsid)
-                except _interpqueues.QueueNotFoundError:
-                    raise  # re-raise
-                except _interpqueues.QueueError:
-                    continue
-                except ModuleNotFoundError:
-                    # interpreters.queues doesn't exist, which means
-                    # QueueEmpty doesn't.  Act as though it does.
-                    continue
-                else:
-                    break
-            (res, excdata), pickled, unboundop = obj
-            assert unboundop is None, unboundop
-            if excdata is not None:
-                assert res is None, res
-                assert pickled
-                assert exc_wrapper is not None
+                break
+        (res, excdata), pickled, unboundop = obj
+        assert unboundop is None, unboundop
+        if excdata is not None:
+            assert res is None, res
+            assert pickled
+            assert exc_wrapper is not None
+            try:
                 raise pickle.loads(excdata) from exc_wrapper
-            return pickle.loads(res) if pickled else res
-        finally:
-            exc_wrapper = None
+            finally:
+                exc_wrapper = None
+        return pickle.loads(res) if pickled else res
 
 
 class BrokenInterpreterPool(_thread.BrokenThreadPool):

From 03f8ab47a3726b6294c842b03f0a0bf1ab7ea3b3 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Mon, 31 Mar 2025 10:53:39 +0100
Subject: [PATCH 16/41] test_map_exception: only search for exception that
 captures itself in its own traceback

---
 Lib/test/test_concurrent_futures/executor.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index ac4d5aaa4434c6..47bfda9096b560 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -79,8 +79,9 @@ def test_map_exception(self):
                     var: val
                     for var, val in tb.tb_frame.f_locals.items()
                     if isinstance(val, Exception)
+                    and var in val.__traceback__.tb_frame.f_locals
                 },
-                msg=f"traceback frames should not contain any exception",
+                msg=f"the raised exception's traceback should not contain an exception that captures itself in its own traceback",
             )
 
     @support.requires_resource('walltime')

From ef301226c144bc92c64f3bbc5fb78a8c6177d298 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Mon, 31 Mar 2025 11:42:27 +0100
Subject: [PATCH 17/41] concurrent.futures.process: avoid ref cycle in
 _sendback_result

---
 Lib/concurrent/futures/process.py | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py
index 4847550908adab..e6e7f304f255ca 100644
--- a/Lib/concurrent/futures/process.py
+++ b/Lib/concurrent/futures/process.py
@@ -210,9 +210,13 @@ def _sendback_result(result_queue, work_id, result=None, exception=None,
         result_queue.put(_ResultItem(work_id, result=result,
                                      exception=exception, exit_pid=exit_pid))
     except BaseException as e:
-        exc = _ExceptionWithTraceback(e, e.__traceback__)
-        result_queue.put(_ResultItem(work_id, exception=exc,
-                                     exit_pid=exit_pid))
+        result_queue.put(
+            _ResultItem(
+                work_id,
+                exception=_ExceptionWithTraceback(e, e.__traceback__),
+                exit_pid=exit_pid
+            )
+        )
 
 
 def _process_worker(call_queue, result_queue, initializer, initargs, max_tasks=None):

From 09b08197db97ad31e23289e7cbb920e41c8706af Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Mon, 31 Mar 2025 11:43:47 +0100
Subject: [PATCH 18/41] concurrent.futures.process: avoid ref cycle in
 _process_worker

---
 Lib/concurrent/futures/process.py | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py
index e6e7f304f255ca..e8d701de17855e 100644
--- a/Lib/concurrent/futures/process.py
+++ b/Lib/concurrent/futures/process.py
@@ -257,9 +257,12 @@ def _process_worker(call_queue, result_queue, initializer, initargs, max_tasks=N
         try:
             r = call_item.fn(*call_item.args, **call_item.kwargs)
         except BaseException as e:
-            exc = _ExceptionWithTraceback(e, e.__traceback__)
-            _sendback_result(result_queue, call_item.work_id, exception=exc,
-                             exit_pid=exit_pid)
+            _sendback_result(
+                result_queue,
+                call_item.work_id,
+                exception=_ExceptionWithTraceback(e, e.__traceback__),
+                exit_pid=exit_pid,
+            )
         else:
             _sendback_result(result_queue, call_item.work_id, result=r,
                              exit_pid=exit_pid)

From 4fab860f21bad3615b665723f0a1f43d77ea45f9 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Mon, 31 Mar 2025 12:27:17 +0100
Subject: [PATCH 19/41] format test msg

---
 Lib/test/test_concurrent_futures/executor.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 47bfda9096b560..807b2938fa21d9 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -69,7 +69,7 @@ def test_map_exception(self):
 
         self.assertFalse(
             gc.get_referrers(error),
-            msg="the raised error should not have any referrers",
+            msg="the exception should not have any referrers",
         )
 
         tb = error.__traceback__
@@ -81,7 +81,7 @@ def test_map_exception(self):
                     if isinstance(val, Exception)
                     and var in val.__traceback__.tb_frame.f_locals
                 },
-                msg=f"the raised exception's traceback should not contain an exception that captures itself in its own traceback",
+                msg=f"the exception's traceback should not contain an exception that captures itself in its own traceback",
             )
 
     @support.requires_resource('walltime')

From f5135abb6145d511202cd866f5637e9e0182217e Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Mon, 31 Mar 2025 12:30:04 +0100
Subject: [PATCH 20/41] refactor ZeroDivisionError assert

---
 Lib/test/test_concurrent_futures/executor.py | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 807b2938fa21d9..32aae3f40939b2 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -60,11 +60,11 @@ def test_map_exception(self):
         error = None
         try:
             next(i)
-        except ZeroDivisionError as zero_div_error:
-            error = zero_div_error
-        self.assertIsNotNone(
-            error,
-            msg="next one should raise a ZeroDivisionError",
+        except Exception as e:
+            error = e
+        self.assertTrue(
+            isinstance(error, ZeroDivisionError),
+            msg="next should raise a ZeroDivisionError",
         )
 
         self.assertFalse(

From 855c427bb7cbdbdb13f8a53f524dd80a02b74ef0 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Mon, 31 Mar 2025 12:49:22 +0100
Subject: [PATCH 21/41] Revert "concurrent.futures.process: avoid ref cycle in
 _process_worker"

This reverts commit 09b08197db97ad31e23289e7cbb920e41c8706af.
---
 Lib/concurrent/futures/process.py | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py
index e8d701de17855e..e6e7f304f255ca 100644
--- a/Lib/concurrent/futures/process.py
+++ b/Lib/concurrent/futures/process.py
@@ -257,12 +257,9 @@ def _process_worker(call_queue, result_queue, initializer, initargs, max_tasks=N
         try:
             r = call_item.fn(*call_item.args, **call_item.kwargs)
         except BaseException as e:
-            _sendback_result(
-                result_queue,
-                call_item.work_id,
-                exception=_ExceptionWithTraceback(e, e.__traceback__),
-                exit_pid=exit_pid,
-            )
+            exc = _ExceptionWithTraceback(e, e.__traceback__)
+            _sendback_result(result_queue, call_item.work_id, exception=exc,
+                             exit_pid=exit_pid)
         else:
             _sendback_result(result_queue, call_item.work_id, result=r,
                              exit_pid=exit_pid)

From 4504516459ecd5e1600a12db51b123ef9a789a4e Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Mon, 31 Mar 2025 12:49:37 +0100
Subject: [PATCH 22/41] Revert "concurrent.futures.process: avoid ref cycle in
 _sendback_result"

This reverts commit ef301226c144bc92c64f3bbc5fb78a8c6177d298.
---
 Lib/concurrent/futures/process.py | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py
index e6e7f304f255ca..4847550908adab 100644
--- a/Lib/concurrent/futures/process.py
+++ b/Lib/concurrent/futures/process.py
@@ -210,13 +210,9 @@ def _sendback_result(result_queue, work_id, result=None, exception=None,
         result_queue.put(_ResultItem(work_id, result=result,
                                      exception=exception, exit_pid=exit_pid))
     except BaseException as e:
-        result_queue.put(
-            _ResultItem(
-                work_id,
-                exception=_ExceptionWithTraceback(e, e.__traceback__),
-                exit_pid=exit_pid
-            )
-        )
+        exc = _ExceptionWithTraceback(e, e.__traceback__)
+        result_queue.put(_ResultItem(work_id, exception=exc,
+                                     exit_pid=exit_pid))
 
 
 def _process_worker(call_queue, result_queue, initializer, initargs, max_tasks=None):

From fc7a569a71d53722f40b31a61018541847aa976b Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Tue, 1 Apr 2025 00:01:37 +0100
Subject: [PATCH 23/41] skip referrers test for free-threading build on
 win/linux

---
 Lib/test/test_concurrent_futures/executor.py | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 32aae3f40939b2..699bdffcabd13f 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -1,10 +1,12 @@
 import gc
 import itertools
+import sys
 import threading
 import time
 import weakref
 from concurrent import futures
 from operator import add
+from sysconfig import get_config_var
 from test import support
 from test.support import Py_GIL_DISABLED
 
@@ -67,10 +69,13 @@ def test_map_exception(self):
             msg="next should raise a ZeroDivisionError",
         )
 
-        self.assertFalse(
-            gc.get_referrers(error),
-            msg="the exception should not have any referrers",
-        )
+        # some referrers may remain for free-threading build on Windows/Linux
+        is_free_threading = '--disable-gil' in get_config_var("CONFIG_ARGS")
+        if not is_free_threading or sys.platform not in ("linux", "win32"):
+            self.assertFalse(
+                gc.get_referrers(error),
+                msg="the exception should not have any referrers",
+            )
 
         tb = error.__traceback__
         while (tb := tb.tb_next):

From cae64747fa2954c8cf868695beb094ebee40032c Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Tue, 1 Apr 2025 00:16:11 +0100
Subject: [PATCH 24/41] call gc.collect for free-threading on linux/windows

---
 Lib/test/test_concurrent_futures/executor.py | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 699bdffcabd13f..639461891787d6 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -69,13 +69,17 @@ def test_map_exception(self):
             msg="next should raise a ZeroDivisionError",
         )
 
-        # some referrers may remain for free-threading build on Windows/Linux
-        is_free_threading = '--disable-gil' in get_config_var("CONFIG_ARGS")
-        if not is_free_threading or sys.platform not in ("linux", "win32"):
-            self.assertFalse(
-                gc.get_referrers(error),
-                msg="the exception should not have any referrers",
-            )
+        # a GC collection may be necessary for free-threading build on Windows/Linux
+        if (
+            '--disable-gil' in get_config_var("CONFIG_ARGS")
+            and sys.platform in ("linux", "win32")
+        ):
+            gc.collect()
+
+        self.assertFalse(
+            gc.get_referrers(error),
+            msg="the exception should not have any referrers",
+        )
 
         tb = error.__traceback__
         while (tb := tb.tb_next):

From 4abb239e5b1e9b8f75eb3b263a277ac0d98b05ce Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Tue, 1 Apr 2025 11:52:20 +0100
Subject: [PATCH 25/41] Revert "call gc.collect for free-threading on
 linux/windows"

This reverts commit cae64747fa2954c8cf868695beb094ebee40032c.
---
 Lib/test/test_concurrent_futures/executor.py | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 639461891787d6..699bdffcabd13f 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -69,17 +69,13 @@ def test_map_exception(self):
             msg="next should raise a ZeroDivisionError",
         )
 
-        # a GC collection may be necessary for free-threading build on Windows/Linux
-        if (
-            '--disable-gil' in get_config_var("CONFIG_ARGS")
-            and sys.platform in ("linux", "win32")
-        ):
-            gc.collect()
-
-        self.assertFalse(
-            gc.get_referrers(error),
-            msg="the exception should not have any referrers",
-        )
+        # some referrers may remain for free-threading build on Windows/Linux
+        is_free_threading = '--disable-gil' in get_config_var("CONFIG_ARGS")
+        if not is_free_threading or sys.platform not in ("linux", "win32"):
+            self.assertFalse(
+                gc.get_referrers(error),
+                msg="the exception should not have any referrers",
+            )
 
         tb = error.__traceback__
         while (tb := tb.tb_next):

From 4bc07c082f92c34f475fc38fa08eb2cba811ed62 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Tue, 1 Apr 2025 11:52:30 +0100
Subject: [PATCH 26/41] Revert "skip referrers test for free-threading build on
 win/linux"

This reverts commit fc7a569a71d53722f40b31a61018541847aa976b.
---
 Lib/test/test_concurrent_futures/executor.py | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 699bdffcabd13f..32aae3f40939b2 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -1,12 +1,10 @@
 import gc
 import itertools
-import sys
 import threading
 import time
 import weakref
 from concurrent import futures
 from operator import add
-from sysconfig import get_config_var
 from test import support
 from test.support import Py_GIL_DISABLED
 
@@ -69,13 +67,10 @@ def test_map_exception(self):
             msg="next should raise a ZeroDivisionError",
         )
 
-        # some referrers may remain for free-threading build on Windows/Linux
-        is_free_threading = '--disable-gil' in get_config_var("CONFIG_ARGS")
-        if not is_free_threading or sys.platform not in ("linux", "win32"):
-            self.assertFalse(
-                gc.get_referrers(error),
-                msg="the exception should not have any referrers",
-            )
+        self.assertFalse(
+            gc.get_referrers(error),
+            msg="the exception should not have any referrers",
+        )
 
         tb = error.__traceback__
         while (tb := tb.tb_next):

From 3b00c5ffc5640d65089349e8ad02cf152a748b52 Mon Sep 17 00:00:00 2001
From: Thomas Grainger <tagrain@gmail.com>
Date: Thu, 3 Apr 2025 08:40:08 +0100
Subject: [PATCH 27/41] more gc referrers

---
 Lib/test/test_concurrent_futures/executor.py | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 32aae3f40939b2..611ba62a1edc22 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -6,7 +6,7 @@
 from concurrent import futures
 from operator import add
 from test import support
-from test.support import Py_GIL_DISABLED
+from test.support import Py_GIL_DISABLED, disable_gc
 
 
 def mul(x, y):
@@ -52,6 +52,7 @@ def test_map(self):
                 list(self.executor.map(pow, range(10), range(10), chunksize=3)),
                 list(map(pow, range(10), range(10))))
 
+    @disable_gc()
     def test_map_exception(self):
         i = self.executor.map(divmod, [1, 1, 1, 1], [2, 3, 0, 5])
         self.assertEqual(i.__next__(), (0, 1))
@@ -67,8 +68,9 @@ def test_map_exception(self):
             msg="next should raise a ZeroDivisionError",
         )
 
+        # TODO: remove only for debugging
         self.assertFalse(
-            gc.get_referrers(error),
+            [gc.get_referrers(x) for x in gc.get_referrers(error)],
             msg="the exception should not have any referrers",
         )
 

From 1948eb3526e2a5bebd3acfcaa358c35dfb46f6b7 Mon Sep 17 00:00:00 2001
From: Thomas Grainger <tagrain@gmail.com>
Date: Thu, 3 Apr 2025 09:00:02 +0100
Subject: [PATCH 28/41] even more gc referrers

---
 Lib/test/test_concurrent_futures/executor.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 611ba62a1edc22..251585b45ae97d 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -70,7 +70,11 @@ def test_map_exception(self):
 
         # TODO: remove only for debugging
         self.assertFalse(
-            [gc.get_referrers(x) for x in gc.get_referrers(error)],
+            [
+                gc.get_referrers(y)
+                for x in gc.get_referrers(error)
+                for y in gc.get_referrers(x)
+            ],
             msg="the exception should not have any referrers",
         )
 

From 91849646fafc0c7fa42dba1ac80936f88a13cfd0 Mon Sep 17 00:00:00 2001
From: Thomas Grainger <tagrain@gmail.com>
Date: Fri, 4 Apr 2025 07:56:24 +0100
Subject: [PATCH 29/41] delete a ref to work_item

---
 Lib/concurrent/futures/process.py | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py
index 4847550908adab..6fef6abf7923e5 100644
--- a/Lib/concurrent/futures/process.py
+++ b/Lib/concurrent/futures/process.py
@@ -392,15 +392,18 @@ def add_call_item_to_queue(self):
             else:
                 work_item = self.pending_work_items[work_id]
 
-                if work_item.future.set_running_or_notify_cancel():
-                    self.call_queue.put(_CallItem(work_id,
-                                                  work_item.fn,
-                                                  work_item.args,
-                                                  work_item.kwargs),
-                                        block=True)
-                else:
-                    del self.pending_work_items[work_id]
-                    continue
+                try:
+                    if work_item.future.set_running_or_notify_cancel():
+                        self.call_queue.put(_CallItem(work_id,
+                                                      work_item.fn,
+                                                      work_item.args,
+                                                      work_item.kwargs),
+                                            block=True)
+                    else:
+                        del self.pending_work_items[work_id]
+                        continue
+                finally:
+                    del work_item
 
     def wait_result_broken_or_wakeup(self):
         # Wait for a result to be ready in the result_queue while checking

From 7e5300cc618eaeab6e4f3f7d2f73b47fac109eef Mon Sep 17 00:00:00 2001
From: Thomas Grainger <tagrain@gmail.com>
Date: Fri, 4 Apr 2025 08:24:08 +0100
Subject: [PATCH 30/41] delete reference to result_item before joining process

---
 Lib/concurrent/futures/process.py | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py
index 6fef6abf7923e5..d6adf407c177f7 100644
--- a/Lib/concurrent/futures/process.py
+++ b/Lib/concurrent/futures/process.py
@@ -347,16 +347,16 @@ def run(self):
                 return
             if result_item is not None:
                 self.process_result_item(result_item)
-
-                process_exited = result_item.exit_pid is not None
-                if process_exited:
-                    p = self.processes.pop(result_item.exit_pid)
-                    p.join()
+                exit_pid = result_item.exit_pid
 
                 # Delete reference to result_item to avoid keeping references
                 # while waiting on new results.
                 del result_item
 
+                process_exited = exit_pid is not None
+                if process_exited:
+                    self.processes.pop(exit_pid).join()
+
                 if executor := self.executor_reference():
                     if process_exited:
                         with self.shutdown_lock:

From c5e39ee5c73a48299d251ec73bc3b535803030f2 Mon Sep 17 00:00:00 2001
From: Thomas Grainger <tagrain@gmail.com>
Date: Fri, 4 Apr 2025 08:45:02 +0100
Subject: [PATCH 31/41] unpack ResultItem and WorkItem

---
 Lib/concurrent/futures/process.py | 36 +++++++++++++++++--------------
 1 file changed, 20 insertions(+), 16 deletions(-)

diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py
index d6adf407c177f7..968abefacd762d 100644
--- a/Lib/concurrent/futures/process.py
+++ b/Lib/concurrent/futures/process.py
@@ -346,12 +346,29 @@ def run(self):
                 self.terminate_broken(cause)
                 return
             if result_item is not None:
-                self.process_result_item(result_item)
                 exit_pid = result_item.exit_pid
+                work_id = result_item.work_id
+                exception = result_item.exeption
+                result = result_item.result
+                del result_item
+                # Process the received a result_item. This can be either the PID of a
+                # worker that exited gracefully or a _ResultItem
+
+                # Received a _ResultItem so mark the future as completed.
+                work_item = self.pending_work_items.pop(work_id, None)
+                # work_item can be None if another process terminated (see above)
+                if work_item is not None:
+                    f = work_item.future
+                    del work_item
+                    if exception:
+                        f.set_exception(exception)
+                    else:
+                        f.set_result(result)
+                    del f
 
-                # Delete reference to result_item to avoid keeping references
+                # Delete reference to exception/result to avoid keeping references
                 # while waiting on new results.
-                del result_item
+                del exception, result
 
                 process_exited = exit_pid is not None
                 if process_exited:
@@ -435,19 +452,6 @@ def wait_result_broken_or_wakeup(self):
 
         return result_item, is_broken, cause
 
-    def process_result_item(self, result_item):
-        # Process the received a result_item. This can be either the PID of a
-        # worker that exited gracefully or a _ResultItem
-
-        # Received a _ResultItem so mark the future as completed.
-        work_item = self.pending_work_items.pop(result_item.work_id, None)
-        # work_item can be None if another process terminated (see above)
-        if work_item is not None:
-            if result_item.exception:
-                work_item.future.set_exception(result_item.exception)
-            else:
-                work_item.future.set_result(result_item.result)
-
     def is_shutting_down(self):
         # Check whether we should start shutting down the executor.
         executor = self.executor_reference()

From 548d517339dbebc077bcfac5c6c637253e2bcc2b Mon Sep 17 00:00:00 2001
From: Thomas Grainger <tagrain@gmail.com>
Date: Sat, 5 Apr 2025 05:48:10 +0100
Subject: [PATCH 32/41] fix typo

---
 Lib/concurrent/futures/process.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py
index 968abefacd762d..268aa221d85b67 100644
--- a/Lib/concurrent/futures/process.py
+++ b/Lib/concurrent/futures/process.py
@@ -348,7 +348,7 @@ def run(self):
             if result_item is not None:
                 exit_pid = result_item.exit_pid
                 work_id = result_item.work_id
-                exception = result_item.exeption
+                exception = result_item.exception
                 result = result_item.result
                 del result_item
                 # Process the received a result_item. This can be either the PID of a

From fd9a89e4f670806c40cea3d43d43f8b27f95047a Mon Sep 17 00:00:00 2001
From: Thomas Grainger <tagrain@gmail.com>
Date: Sat, 5 Apr 2025 09:30:32 +0100
Subject: [PATCH 33/41] bit of a hack?

---
 Lib/concurrent/futures/process.py | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py
index 268aa221d85b67..865d7a08bd2d99 100644
--- a/Lib/concurrent/futures/process.py
+++ b/Lib/concurrent/futures/process.py
@@ -358,13 +358,12 @@ def run(self):
                 work_item = self.pending_work_items.pop(work_id, None)
                 # work_item can be None if another process terminated (see above)
                 if work_item is not None:
-                    f = work_item.future
+                    f_boxed = [work_item.future]
                     del work_item
                     if exception:
-                        f.set_exception(exception)
+                        f_boxed.pop().set_exception(exception)
                     else:
-                        f.set_result(result)
-                    del f
+                        f_boxed.pop().set_result(result)
 
                 # Delete reference to exception/result to avoid keeping references
                 # while waiting on new results.

From dbaa0448d0cc97a4a92824f812b1d5cf3a52d833 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Mon, 7 Apr 2025 11:52:28 +0100
Subject: [PATCH 34/41] Revert investigations

---
 Lib/concurrent/futures/process.py            | 66 +++++++++-----------
 Lib/test/test_concurrent_futures/executor.py | 10 +--
 2 files changed, 32 insertions(+), 44 deletions(-)

diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py
index 865d7a08bd2d99..4847550908adab 100644
--- a/Lib/concurrent/futures/process.py
+++ b/Lib/concurrent/futures/process.py
@@ -346,32 +346,16 @@ def run(self):
                 self.terminate_broken(cause)
                 return
             if result_item is not None:
-                exit_pid = result_item.exit_pid
-                work_id = result_item.work_id
-                exception = result_item.exception
-                result = result_item.result
-                del result_item
-                # Process the received a result_item. This can be either the PID of a
-                # worker that exited gracefully or a _ResultItem
-
-                # Received a _ResultItem so mark the future as completed.
-                work_item = self.pending_work_items.pop(work_id, None)
-                # work_item can be None if another process terminated (see above)
-                if work_item is not None:
-                    f_boxed = [work_item.future]
-                    del work_item
-                    if exception:
-                        f_boxed.pop().set_exception(exception)
-                    else:
-                        f_boxed.pop().set_result(result)
-
-                # Delete reference to exception/result to avoid keeping references
-                # while waiting on new results.
-                del exception, result
+                self.process_result_item(result_item)
 
-                process_exited = exit_pid is not None
+                process_exited = result_item.exit_pid is not None
                 if process_exited:
-                    self.processes.pop(exit_pid).join()
+                    p = self.processes.pop(result_item.exit_pid)
+                    p.join()
+
+                # Delete reference to result_item to avoid keeping references
+                # while waiting on new results.
+                del result_item
 
                 if executor := self.executor_reference():
                     if process_exited:
@@ -408,18 +392,15 @@ def add_call_item_to_queue(self):
             else:
                 work_item = self.pending_work_items[work_id]
 
-                try:
-                    if work_item.future.set_running_or_notify_cancel():
-                        self.call_queue.put(_CallItem(work_id,
-                                                      work_item.fn,
-                                                      work_item.args,
-                                                      work_item.kwargs),
-                                            block=True)
-                    else:
-                        del self.pending_work_items[work_id]
-                        continue
-                finally:
-                    del work_item
+                if work_item.future.set_running_or_notify_cancel():
+                    self.call_queue.put(_CallItem(work_id,
+                                                  work_item.fn,
+                                                  work_item.args,
+                                                  work_item.kwargs),
+                                        block=True)
+                else:
+                    del self.pending_work_items[work_id]
+                    continue
 
     def wait_result_broken_or_wakeup(self):
         # Wait for a result to be ready in the result_queue while checking
@@ -451,6 +432,19 @@ def wait_result_broken_or_wakeup(self):
 
         return result_item, is_broken, cause
 
+    def process_result_item(self, result_item):
+        # Process the received a result_item. This can be either the PID of a
+        # worker that exited gracefully or a _ResultItem
+
+        # Received a _ResultItem so mark the future as completed.
+        work_item = self.pending_work_items.pop(result_item.work_id, None)
+        # work_item can be None if another process terminated (see above)
+        if work_item is not None:
+            if result_item.exception:
+                work_item.future.set_exception(result_item.exception)
+            else:
+                work_item.future.set_result(result_item.result)
+
     def is_shutting_down(self):
         # Check whether we should start shutting down the executor.
         executor = self.executor_reference()
diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 251585b45ae97d..32aae3f40939b2 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -6,7 +6,7 @@
 from concurrent import futures
 from operator import add
 from test import support
-from test.support import Py_GIL_DISABLED, disable_gc
+from test.support import Py_GIL_DISABLED
 
 
 def mul(x, y):
@@ -52,7 +52,6 @@ def test_map(self):
                 list(self.executor.map(pow, range(10), range(10), chunksize=3)),
                 list(map(pow, range(10), range(10))))
 
-    @disable_gc()
     def test_map_exception(self):
         i = self.executor.map(divmod, [1, 1, 1, 1], [2, 3, 0, 5])
         self.assertEqual(i.__next__(), (0, 1))
@@ -68,13 +67,8 @@ def test_map_exception(self):
             msg="next should raise a ZeroDivisionError",
         )
 
-        # TODO: remove only for debugging
         self.assertFalse(
-            [
-                gc.get_referrers(y)
-                for x in gc.get_referrers(error)
-                for y in gc.get_referrers(x)
-            ],
+            gc.get_referrers(error),
             msg="the exception should not have any referrers",
         )
 

From 869e4b750255cd2a9cc145d2e2e7718c0a202afe Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Mon, 7 Apr 2025 12:00:15 +0100
Subject: [PATCH 35/41] pause before checking referrers

---
 Lib/test/test_concurrent_futures/executor.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 32aae3f40939b2..ac10118454d504 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -67,6 +67,8 @@ def test_map_exception(self):
             msg="next should raise a ZeroDivisionError",
         )
 
+        # free-threading builds need this pause on Ubuntu (ARM) and Windows
+        time.sleep(1)
         self.assertFalse(
             gc.get_referrers(error),
             msg="the exception should not have any referrers",

From 1ee9bf4d089bdcd3ee5e064420e2dec7a2e627e0 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Mon, 7 Apr 2025 14:23:39 +0100
Subject: [PATCH 36/41] add comment about the avoided ref cycle with
 exc_wrapper

---
 Lib/concurrent/futures/interpreter.py | 1 +
 Modules/_opcode-488016f1.o.tmp        | 0
 2 files changed, 1 insertion(+)
 create mode 100644 Modules/_opcode-488016f1.o.tmp

diff --git a/Lib/concurrent/futures/interpreter.py b/Lib/concurrent/futures/interpreter.py
index 1c1187272a26ed..030c36ec9b31f1 100644
--- a/Lib/concurrent/futures/interpreter.py
+++ b/Lib/concurrent/futures/interpreter.py
@@ -208,6 +208,7 @@ def run(self, task):
             try:
                 raise pickle.loads(excdata) from exc_wrapper
             finally:
+                # avoid a ref cycle where exc_wrapper is captured in its traceback
                 exc_wrapper = None
         return pickle.loads(res) if pickled else res
 
diff --git a/Modules/_opcode-488016f1.o.tmp b/Modules/_opcode-488016f1.o.tmp
new file mode 100644
index 00000000000000..e69de29bb2d1d6

From 95765f678582d668120fd662e1bae74e999f1681 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Mon, 7 Apr 2025 14:27:24 +0100
Subject: [PATCH 37/41] format test

---
 Lib/test/test_concurrent_futures/executor.py | 11 ++++++-----
 Modules/_opcode-488016f1.o.tmp               |  0
 2 files changed, 6 insertions(+), 5 deletions(-)
 delete mode 100644 Modules/_opcode-488016f1.o.tmp

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index ac10118454d504..4d59c49e69fa1a 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -57,24 +57,25 @@ def test_map_exception(self):
         self.assertEqual(i.__next__(), (0, 1))
         self.assertEqual(i.__next__(), (0, 1))
 
-        error = None
+        exception = None
         try:
             next(i)
         except Exception as e:
-            error = e
+            exception = e
         self.assertTrue(
-            isinstance(error, ZeroDivisionError),
+            isinstance(exception, ZeroDivisionError),
             msg="next should raise a ZeroDivisionError",
         )
 
         # free-threading builds need this pause on Ubuntu (ARM) and Windows
         time.sleep(1)
+
         self.assertFalse(
-            gc.get_referrers(error),
+            gc.get_referrers(exception),
             msg="the exception should not have any referrers",
         )
 
-        tb = error.__traceback__
+        tb = exception.__traceback__
         while (tb := tb.tb_next):
             self.assertFalse(
                 {
diff --git a/Modules/_opcode-488016f1.o.tmp b/Modules/_opcode-488016f1.o.tmp
deleted file mode 100644
index e69de29bb2d1d6..00000000000000

From a5c6b17656dbb0332847640e61603935e95e2ed5 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Mon, 7 Apr 2025 18:01:48 +0100
Subject: [PATCH 38/41] make the self-captured exceptions check not rely on var
 name

---
 Lib/test/test_concurrent_futures/executor.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 4d59c49e69fa1a..82fb5d9c455663 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -82,7 +82,7 @@ def test_map_exception(self):
                     var: val
                     for var, val in tb.tb_frame.f_locals.items()
                     if isinstance(val, Exception)
-                    and var in val.__traceback__.tb_frame.f_locals
+                    and val.__traceback__.tb_frame is tb.tb_frame
                 },
                 msg=f"the exception's traceback should not contain an exception that captures itself in its own traceback",
             )

From 0f8748c7dfb5230cce0958846046af74406559e4 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Mon, 7 Apr 2025 20:02:29 +0100
Subject: [PATCH 39/41] use traceback.walk_tb

---
 Lib/test/test_concurrent_futures/executor.py | 26 +++++++++++---------
 1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 82fb5d9c455663..4b15f99dcbc1a8 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -2,9 +2,10 @@
 import itertools
 import threading
 import time
+import traceback
 import weakref
 from concurrent import futures
-from operator import add
+from operator import add, itemgetter
 from test import support
 from test.support import Py_GIL_DISABLED
 
@@ -75,17 +76,18 @@ def test_map_exception(self):
             msg="the exception should not have any referrers",
         )
 
-        tb = exception.__traceback__
-        while (tb := tb.tb_next):
-            self.assertFalse(
-                {
-                    var: val
-                    for var, val in tb.tb_frame.f_locals.items()
-                    if isinstance(val, Exception)
-                    and val.__traceback__.tb_frame is tb.tb_frame
-                },
-                msg=f"the exception's traceback should not contain an exception that captures itself in its own traceback",
-            )
+        frames = map(itemgetter(0), traceback.walk_tb(exception.__traceback__))
+        next(frames)
+        self.assertFalse(
+            [
+                (var, val)
+                for frame in frames
+                for var, val in frame.f_locals.items()
+                if isinstance(val, Exception)
+                and frame in map(itemgetter(0), traceback.walk_tb(val.__traceback__))
+            ],
+            msg=f"the exception's traceback should not contain an exception that captures itself in its own traceback",
+        )
 
     @support.requires_resource('walltime')
     def test_map_timeout(self):

From 85a3c369fba78367b76b92c46b518d4e623ab8d4 Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Mon, 7 Apr 2025 20:20:48 +0100
Subject: [PATCH 40/41] comment the skipping of the current frame

---
 Lib/test/test_concurrent_futures/executor.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 4b15f99dcbc1a8..f348ef998812ad 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -77,7 +77,10 @@ def test_map_exception(self):
         )
 
         frames = map(itemgetter(0), traceback.walk_tb(exception.__traceback__))
+
+        # skip current frame
         next(frames)
+
         self.assertFalse(
             [
                 (var, val)

From 82542f398da251e3d3fd9fad0ba8b93a1a92b92f Mon Sep 17 00:00:00 2001
From: ebonnal <bonnal.enzo.dev@gmail.com>
Date: Wed, 23 Apr 2025 13:13:16 +0100
Subject: [PATCH 41/41] test_map_exception: improve readability

---
 Lib/test/test_concurrent_futures/executor.py | 25 ++++++++++----------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index f348ef998812ad..6cdd8f4fd61537 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -5,7 +5,7 @@
 import traceback
 import weakref
 from concurrent import futures
-from operator import add, itemgetter
+from operator import add
 from test import support
 from test.support import Py_GIL_DISABLED
 
@@ -60,15 +60,15 @@ def test_map_exception(self):
 
         exception = None
         try:
-            next(i)
+            i.__next__()
         except Exception as e:
             exception = e
         self.assertTrue(
             isinstance(exception, ZeroDivisionError),
-            msg="next should raise a ZeroDivisionError",
+            msg="should raise a ZeroDivisionError",
         )
 
-        # free-threading builds need this pause on Ubuntu (ARM) and Windows
+        # pause needed for free-threading builds on Ubuntu (ARM) and Windows
         time.sleep(1)
 
         self.assertFalse(
@@ -76,20 +76,21 @@ def test_map_exception(self):
             msg="the exception should not have any referrers",
         )
 
-        frames = map(itemgetter(0), traceback.walk_tb(exception.__traceback__))
-
-        # skip current frame
-        next(frames)
-
         self.assertFalse(
             [
                 (var, val)
-                for frame in frames
+                # go through the frames of the exception's traceback
+                for frame, _ in traceback.walk_tb(exception.__traceback__)
+                # skipping the current frame
+                if frame is not exception.__traceback__.tb_frame
+                # go through the locals captured in that frame
                 for var, val in frame.f_locals.items()
+                # check if one of them is an exception
                 if isinstance(val, Exception)
-                and frame in map(itemgetter(0), traceback.walk_tb(val.__traceback__))
+                # check if it is captured in its own traceback
+                and frame is val.__traceback__.tb_frame
             ],
-            msg=f"the exception's traceback should not contain an exception that captures itself in its own traceback",
+            msg=f"the exception's traceback should not contain an exception captured in its own traceback",
         )
 
     @support.requires_resource('walltime')