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bpo-44895: libregrtest: refleak check clears types later#28113

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vstinner merged 1 commit intopython:mainfrom
vstinner:refleak
Sep 1, 2021
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bpo-44895: libregrtest: refleak check clears types later#28113
vstinner merged 1 commit intopython:mainfrom
vstinner:refleak

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@vstinner vstinner commented Sep 1, 2021 •
edited by bedevere-bot
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libregrtest now clears the type cache later to reduce the risk of
false alarm when checking for reference leaks. Previously, the type
cache was cleared too early and libregrtest raised a false alarm
about reference leaks under very specific conditions.

Move also support.gc_collect() outside clear/cleanup functions to
make the garbage collection more explicit.

Co-Authored-By: Irit Katriel 1055913+iritkatriel@users.noreply.github.com

https://bugs.python.org/issue44895

@vstinner @iritkatriel
bpo-44895: libregrtest: refleak check clears types later
2a1019a 
libregrtest now clears the type cache later to reduce the risk of
false alarm when checking for reference leaks. Previously, the type
cache was cleared too early and libregrtest raised a false alarm
about reference leaks under very specific conditions.

Move also support.gc_collect() outside clear/cleanup functions to
make the garbage collection more explicit.

Co-Authored-By: Irit Katriel <1055913+iritkatriel@users.noreply.github.com>
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vstinner commented Sep 1, 2021

@iritkatriel: Would you mind to check if this change fix https://bugs.python.org/issue44895 for you? It seems like you are the only one able to reproduce https://bugs.python.org/issue44895 :-)

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iritkatriel commented Sep 1, 2021

checking!

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iritkatriel approved these changes Sep 1, 2021
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Yeah!

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vstinner commented Sep 1, 2021

Using the following patch:

diff --git a/Lib/test/libregrtest/refleak.py b/Lib/test/libregrtest/refleak.py
index 096b5381cd..b82f0e6aaa 100644
--- a/Lib/test/libregrtest/refleak.py
+++ b/Lib/test/libregrtest/refleak.py
@@ -126,7 +126,7 @@ def check_rc_deltas(deltas):
         #
         #   [5, 5, 6]
         #   [10, 1, 1]
-        return all(delta >= 1 for delta in deltas)
+        return any(delta >= 1 for delta in deltas)
 
     def check_fd_deltas(deltas):
         return any(deltas)

I reproduce the bug using refleak.py attached to https://bugs.python.org/issue44895:

$ git switch main
$ git apply patch
$ ./python refleak.py 
-- 1 --
beginning 6 repetitions
123456
......
test leaked [-4, 4, -4] references, sum=-4
test leaked [-4, 4, -4] memory blocks, sum=-4

With this PR, refleak.py runs forever:

$ git switch refleak   # This PR
$ git apply patch
$ ./python refleak.py 
(...)
-- 143 --
beginning 6 repetitions
123456
......
-- 144 --
beginning 6 repetitions
123456
......
(...)

@vstinner vstinner merged commit 679cb47 into python:main Sep 1, 2021
@vstinner vstinner deleted the refleak branch September 1, 2021 15:45
sakibguy added a commit to sakibguy/cpython that referenced this pull request Sep 2, 2021
@sakibguy
Merge pull request #3 from python/main
02d1195 
bpo-44895: libregrtest: refleak check clears types later (pythonGH-28113)
@iritkatriel iritkatriel mentioned this pull request Mar 22, 2023
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