From 32768cb819c1e31efa6696ce508a033ddf0af96d Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Tue, 13 Oct 2026 22:40:57 +0200
Subject: [PATCH 1/2] gh-157649: Use more warmups in test_cext to check for
 refleaks

Use 3 warmups instead of 1 before checking for reference leaks. Also,
always call gc.collect() before reading sys.gettotalrefcount().
---
 Lib/test/test_cext/runtests.py | 42 ++++++++++++++++++++++------------
 1 file changed, 27 insertions(+), 15 deletions(-)

diff --git a/Lib/test/test_cext/runtests.py b/Lib/test/test_cext/runtests.py
index e8288ee5e11e44b..a080db60b6c11f4 100644
--- a/Lib/test/test_cext/runtests.py
+++ b/Lib/test/test_cext/runtests.py
@@ -19,6 +19,32 @@ def run_tests(testmod, verbose=True):
     print(flush=True)
 
 
+def run_refleak_tests(testmod):
+    # Run tests and check for reference leaks
+    warmups = 3
+    runs = 3
+    repcount = warmups + runs
+    refcount = array.array('q', [0] * repcount)
+    rep_range = tuple(range(repcount))
+
+    for i in rep_range:
+        print(f"Run #{i + 1}", flush=True)
+        run_tests(testmod)
+        gc.collect()
+        refcount[i] = sys.gettotalrefcount()
+
+    first = refcount[0]
+    for i in rep_range:
+        refcount[i] -= first
+
+    deltas = list(refcount[warmups:])
+    if all(delta >= 1 for delta in deltas):
+        print(f'ERROR: Tests leaked {deltas} references')
+        sys.exit(1)
+    elif any(deltas):
+        print(f'WARNING: Tests leaked {deltas} references (this is fine)')
+
+
 def main():
     if len(sys.argv) < 2:
         print("usage: python runtests.py TEST_MODULE_NAME")
@@ -45,21 +71,7 @@ def main():
         print()
 
     if hasattr(sys, 'gettotalrefcount'):
-        # First run to warm up Python. For example, test_datetime() imports
-        # the datetime module.
-        run_tests(testmod, verbose=False)
-
-        refcount = array.array('q', [0, 0])
-        gc.collect()
-
-        # Check for reference leak
-        refcount[0] = sys.gettotalrefcount()
-        run_tests(testmod)
-        refcount[1] = sys.gettotalrefcount()
-
-        diff = refcount[1] - refcount[0]
-        if diff >= 1:
-            raise AssertionError(f'Tests leaked {diff} references')
+        run_refleak_tests(testmod)
     else:
         run_tests(testmod)
 

From f6d0d1be724570c7ee127970e638c61117f2443f Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Tue, 13 Oct 2026 22:50:35 +0200
Subject: [PATCH 2/2] Compute differences

---
 Lib/test/test_cext/runtests.py | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/Lib/test/test_cext/runtests.py b/Lib/test/test_cext/runtests.py
index a080db60b6c11f4..6700b410b7d7a78 100644
--- a/Lib/test/test_cext/runtests.py
+++ b/Lib/test/test_cext/runtests.py
@@ -33,9 +33,13 @@ def run_refleak_tests(testmod):
         gc.collect()
         refcount[i] = sys.gettotalrefcount()
 
-    first = refcount[0]
+    # Compute differences
+    previous = None
     for i in rep_range:
-        refcount[i] -= first
+        value = refcount[i]
+        if previous is not None:
+           refcount[i] = value - previous
+        previous = value
 
     deltas = list(refcount[warmups:])
     if all(delta >= 1 for delta in deltas):