gh-111654: remove redundant decref on the eval stack value #111655

aisk · 2023-11-02T17:06:48Z

This is just like #109123, but for another OP code. In the error path, the class_dict is still on the value stack, and the error unwinding process will call decref on it. So we should remove the decref in error path, or there will be a double decref, and cause the ref count to negative in the GC process, and leads to the runtime crash.

Issue: redundant decref on the eval stack value in LOAD_FROM_DICT_OR_DEREF in error path #111654

…DEREF in error path

iritkatriel · 2023-11-02T17:42:23Z

Python/bytecodes.c

@@ -1550,6 +1548,7 @@ dummy_func(
                }
                Py_INCREF(value);
            }
+            Py_DECREF(class_dict);


This DECREF won't happen if we GOTO_ERROR on line 1547. Is that the idea?

Yes, this is the expected behavior. I'll add some notes on the first comment.

JelleZijlstra

Thanks!

miss-islington-app · 2023-11-03T04:06:55Z

Thanks @aisk for the PR, and @JelleZijlstra for merging it 🌮🎉.. I'm working now to backport this PR to: 3.12.
🐍🍒⛏🤖

miss-islington-app · 2023-11-03T04:06:58Z

Sorry, @aisk and @JelleZijlstra, I could not cleanly backport this to 3.12 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 3a1b09e6d070778d78d81084f88d37377d38ee9b 3.12

bedevere-app · 2023-11-03T04:12:59Z

GH-111674 is a backport of this pull request to the 3.12 branch.

…DEREF (pythonGH-111655) (cherry picked from commit 3a1b09e) Co-authored-by: AN Long <aisk@users.noreply.github.com>

bedevere-bot · 2023-11-03T05:02:56Z

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot s390x RHEL7 3.x has failed when building commit 3a1b09e.

What do you need to do:

Don't panic.
Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/179/builds/5864) and take a look at the build logs.
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Summary of the results of the build (if available):

==

Click to see traceback logs

remote: Enumerating objects: 14, done.�[K
remote: Counting objects:   7% (1/14)�[K
remote: Counting objects:  14% (2/14)�[K
remote: Counting objects:  21% (3/14)�[K
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remote: Counting objects: 100% (14/14), done.�[K
remote: Compressing objects:   8% (1/12)�[K
remote: Compressing objects:  16% (2/12)�[K
remote: Compressing objects:  25% (3/12)�[K
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remote: Compressing objects: 100% (12/12)�[K
remote: Compressing objects: 100% (12/12), done.�[K
remote: Total 14 (delta 4), reused 5 (delta 2), pack-reused 0�[K
From https://github.com/python/cpython
 * branch            main       -> FETCH_HEAD
Note: checking out '3a1b09e6d070778d78d81084f88d37377d38ee9b'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -b with the checkout command again. Example:

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HEAD is now at 3a1b09e... gh-111654: remove redundant decref in LOAD_FROM_DICT_OR_DEREF (#111655)
Switched to and reset branch 'main'

Objects/unicodeobject.c: In function ‘unicode_endswith’:
Objects/unicodeobject.c:13021:23: warning: ‘subobj’ may be used uninitialized in this function [-Wmaybe-uninitialized]
             substring = PyTuple_GET_ITEM(subobj, i);
                       ^
Objects/unicodeobject.c: In function ‘unicode_startswith’:
Objects/unicodeobject.c:12967:23: warning: ‘subobj’ may be used uninitialized in this function [-Wmaybe-uninitialized]
             substring = PyTuple_GET_ITEM(subobj, i);
                       ^
Python/instrumentation.c: In function ‘allocate_instrumentation_data’:
Python/instrumentation.c:1489:9: warning: missing braces around initializer [-Wmissing-braces]
         code->_co_monitoring->local_monitors = (_Py_LocalMonitors){ 0 };
         ^
Python/instrumentation.c:1489:9: warning: (near initialization for ‘(anonymous).tools’) [-Wmissing-braces]
Python/instrumentation.c:1490:9: warning: missing braces around initializer [-Wmissing-braces]
         code->_co_monitoring->active_monitors = (_Py_LocalMonitors){ 0 };
         ^
Python/instrumentation.c:1490:9: warning: (near initialization for ‘(anonymous).tools’) [-Wmissing-braces]
./Modules/_xxinterpchannelsmodule.c: In function ‘_channel_get_info’:
./Modules/_xxinterpchannelsmodule.c:2129:21: warning: missing braces around initializer [-Wmissing-braces]
     *info = (struct channel_info){0};
                     ^
./Modules/_xxinterpchannelsmodule.c:2129:21: warning: (near initialization for ‘(anonymous).status’) [-Wmissing-braces]

make: *** [buildbottest] Error 3

bedevere-bot · 2023-11-03T05:07:44Z

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Windows11 Bigmem 3.x has failed when building commit 3a1b09e.

What do you need to do:

Don't panic.
Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/1079/builds/2652) and take a look at the build logs.
Check if the failure is related to this commit (3a1b09e) or if it is a false positive.
If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/1079/builds/2652

Summary of the results of the build (if available):

==

Click to see traceback logs

remote: Enumerating objects: 14, done.        
remote: Counting objects:   7% (1/14)        
remote: Counting objects:  14% (2/14)        
remote: Counting objects:  21% (3/14)        
remote: Counting objects:  28% (4/14)        
remote: Counting objects:  35% (5/14)        
remote: Counting objects:  42% (6/14)        
remote: Counting objects:  50% (7/14)        
remote: Counting objects:  57% (8/14)        
remote: Counting objects:  64% (9/14)        
remote: Counting objects:  71% (10/14)        
remote: Counting objects:  78% (11/14)        
remote: Counting objects:  85% (12/14)        
remote: Counting objects:  92% (13/14)        
remote: Counting objects: 100% (14/14)        
remote: Counting objects: 100% (14/14), done.        
remote: Compressing objects:   8% (1/12)        
remote: Compressing objects:  16% (2/12)        
remote: Compressing objects:  25% (3/12)        
remote: Compressing objects:  33% (4/12)        
remote: Compressing objects:  41% (5/12)        
remote: Compressing objects:  50% (6/12)        
remote: Compressing objects:  58% (7/12)        
remote: Compressing objects:  66% (8/12)        
remote: Compressing objects:  75% (9/12)        
remote: Compressing objects:  83% (10/12)        
remote: Compressing objects:  91% (11/12)        
remote: Compressing objects: 100% (12/12)        
remote: Compressing objects: 100% (12/12), done.        
remote: Total 14 (delta 4), reused 5 (delta 2), pack-reused 0        
From https://github.com/python/cpython
 * branch                  main       -> FETCH_HEAD
Note: switching to '3a1b09e6d070778d78d81084f88d37377d38ee9b'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by switching back to a branch.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -c with the switch command. Example:

  git switch -c <new-branch-name>

Or undo this operation with:

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Turn off this advice by setting config variable advice.detachedHead to false

HEAD is now at 3a1b09e6d0 gh-111654: remove redundant decref in LOAD_FROM_DICT_OR_DEREF (#111655)
Switched to and reset branch 'main'

Could Not Find R:\buildarea\3.x.ambv-bb-win11.bigmem\build\Lib\*.pyc
The system cannot find the file specified.
Could Not Find R:\buildarea\3.x.ambv-bb-win11.bigmem\build\PCbuild\python*.zip

Could Not Find R:\buildarea\3.x.ambv-bb-win11.bigmem\build\PCbuild\python*.zip

…ython#111655)

…H-111655) (#111674) (cherry picked from commit 3a1b09e) Co-authored-by: AN Long <aisk@users.noreply.github.com>

…ython#111655)

remove redundant decref on the eval stack value in LOAD_FROM_DICT_OR_…

036fc0f

…DEREF in error path

aisk requested a review from iritkatriel as a code owner November 2, 2023 17:06

bedevere-app bot added the awaiting review label Nov 2, 2023

bedevere-app bot mentioned this pull request Nov 2, 2023

redundant decref on the eval stack value in LOAD_FROM_DICT_OR_DEREF in error path #111654

Closed

aisk changed the title ~~gh-111654: remove redundant decref on the eval stack value in LOAD_FROM_DICT_OR_…~~ gh-111654: remove redundant decref on the eval stack value Nov 2, 2023

iritkatriel reviewed Nov 2, 2023

View reviewed changes

JelleZijlstra self-requested a review November 2, 2023 19:15

JelleZijlstra approved these changes Nov 3, 2023

View reviewed changes

bedevere-app bot added awaiting merge and removed awaiting review labels Nov 3, 2023

JelleZijlstra added needs backport to 3.12 bug and security fixes and removed awaiting merge labels Nov 3, 2023

JelleZijlstra merged commit 3a1b09e into python:main Nov 3, 2023
35 checks passed

miss-islington-app bot assigned JelleZijlstra Nov 3, 2023

bedevere-app bot removed the needs backport to 3.12 bug and security fixes label Nov 3, 2023

FullteaR pushed a commit to FullteaR/cpython that referenced this pull request Nov 3, 2023

pythongh-111654: remove redundant decref in LOAD_FROM_DICT_OR_DEREF (p…

73584a0

…ython#111655)

JelleZijlstra added a commit that referenced this pull request Nov 3, 2023

[3.12] gh-111654: remove redundant decref in LOAD_FROM_DICT_OR_DEREF (G…

1a95ad6

…H-111655) (#111674) (cherry picked from commit 3a1b09e) Co-authored-by: AN Long <aisk@users.noreply.github.com>

aisk deleted the fix-crash branch November 9, 2023 16:04

aisk added a commit to aisk/cpython that referenced this pull request Feb 11, 2024

pythongh-111654: remove redundant decref in LOAD_FROM_DICT_OR_DEREF (p…

5b8aa03

…ython#111655)

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gh-111654: remove redundant decref on the eval stack value #111655

gh-111654: remove redundant decref on the eval stack value #111655

aisk commented Nov 2, 2023 •

edited

iritkatriel Nov 2, 2023 •

edited

aisk Nov 2, 2023

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gh-111654: remove redundant decref on the eval stack value #111655

gh-111654: remove redundant decref on the eval stack value #111655

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aisk commented Nov 2, 2023 • edited

iritkatriel Nov 2, 2023 • edited

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aisk commented Nov 2, 2023 •

edited

iritkatriel Nov 2, 2023 •

edited