[3.10] gh-95166: cancel map waited on future on timeout (GH-95169) (GH-95375)

Co-authored-by: Thomas Grainger <tagrain@gmail.com>
Co-authored-by: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>

1 files changed, 14 insertions, 2 deletions

diff --git a/Lib/concurrent/futures/_base.py b/Lib/concurrent/futures/_base.py
index cf119ac643..a329e74d11 100644
--- a/Lib/concurrent/futures/_base.py
+++ b/Lib/concurrent/futures/_base.py
@@ -312,6 +312,18 @@ def wait(fs, timeout=None, return_when=ALL_COMPLETED):
     done.update(waiter.finished_futures)
     return DoneAndNotDoneFutures(done, fs - done)
 
+
+def _result_or_cancel(fut, timeout=None):
+    try:
+        try:
+            return fut.result(timeout)
+        finally:
+            fut.cancel()
+    finally:
+        # Break a reference cycle with the exception in self._exception
+        del fut
+
+
 class Future(object):
     """Represents the result of an asynchronous computation."""
 
@@ -606,9 +618,9 @@ class Executor(object):
                 while fs:
                     # Careful not to keep a reference to the popped future
                     if timeout is None:
-                        yield fs.pop().result()
+                        yield _result_or_cancel(fs.pop())
                     else:
-                        yield fs.pop().result(end_time - time.monotonic())
+                        yield _result_or_cancel(fs.pop(), end_time - time.monotonic())
             finally:
                 for future in fs:
                     future.cancel()