> So the first non-zero alloc_delta really has a snowball effect, as it creates new memory block which will produce a non-zero alloc_delta on the next run, etc.

Oh, I suspected an issue around this code but I was unable to explain it. I focused strongly on test_current_frames(), whereas this function is just fine... It's really strange that the bug only triggers on very specific conditions.

"""
Actually, it's quite simple :-) On 64-bit Python:

>>> id(82914 - 82913) == id(1)
True

On 32-bit Python:

>>> id(82914 - 82913) == id(1)
False
"""

That's very strange.

Another workaround:

diff --git a/Lib/test/libregrtest/refleak.py b/Lib/test/libregrtest/refleak.py
index efe52107cb..35d3f8e42d 100644
--- a/Lib/test/libregrtest/refleak.py
+++ b/Lib/test/libregrtest/refleak.py
@@ -56,9 +56,10 @@ def dash_R(the_module, test, indirect_test, huntrleaks):
                                                          abcs)
         print('.', end='', file=sys.stderr, flush=True)
         if i >= nwarmup:
-            rc_deltas[i] = rc_after - rc_before
-            alloc_deltas[i] = alloc_after - alloc_before
-            fd_deltas[i] = fd_after - fd_before
+            def maybe_small_long(x): return int(str(x))
+            rc_deltas[i] = maybe_small_long(rc_after - rc_before)
+            alloc_deltas[i] = maybe_small_long(alloc_after - alloc_before)
+            fd_deltas[i] = maybe_small_long(fd_after - fd_before)
         alloc_before = alloc_after
         rc_before = rc_after
         fd_before = fd_after