Valgrind: conditional jump depends on uninitialized value at importing json module (PyUnicode_Decode (unicodeobject.c:3275))

[abkein]

Bug report

Bug description:

I'm running python MPI (using mpi4py) program under valgrind. I'm unable to provide code, causing the error, because it is large and I dont know in which part it happens. But I think it should not depend on my actual code, b/c it happens every time I run different code.

What I get is

==59009== Thread 1:
==59009== Conditional jump or move depends on uninitialised value(s)
==59009==    at 0x50CD551: PyUnicode_Decode (unicodeobject.c:3275)
==59009==    by 0x50BEB1E: UnknownInlinedFun (unicodeobject.c:3148)
==59009==    by 0x50BEB1E: UnknownInlinedFun (unicodeobject.c:14515)
==59009==    by 0x50BEB1E: unicode_new (unicodeobject.c.h:1497)
==59009==    by 0x50402E8: UnknownInlinedFun (typeobject.c:1665)
==59009==    by 0x50402E8: _PyObject_MakeTpCall (call.c:240)
==59009==    by 0x5049094: _PyEval_EvalFrameDefault (bytecodes.c:2715)
==59009==    by 0x5042E84: UnknownInlinedFun (pycore_ceval.h:89)
==59009==    by 0x5042E84: UnknownInlinedFun (ceval.c:1683)
==59009==    by 0x5042E84: UnknownInlinedFun (call.c:419)
==59009==    by 0x5042E84: _PyObject_FastCallDictTstate (call.c:133)
==59009==    by 0x5081D58: UnknownInlinedFun (call.c:508)
==59009==    by 0x5081D58: slot_tp_init (typeobject.c:9023)
==59009==    by 0x50403BA: UnknownInlinedFun (typeobject.c:1677)
==59009==    by 0x50403BA: _PyObject_MakeTpCall (call.c:240)
==59009==    by 0x5049094: _PyEval_EvalFrameDefault (bytecodes.c:2715)
==59009==    by 0x511F331: PyEval_EvalCode (ceval.c:578)
==59009==    by 0x513B558: UnknownInlinedFun (bltinmodule.c:1096)
==59009==    by 0x513B558: builtin_exec (bltinmodule.c.h:586)
==59009==    by 0x506522D: cfunction_vectorcall_FASTCALL_KEYWORDS (methodobject.c:438)
==59009==    by 0x504E315: UnknownInlinedFun (call.c:387)
==59009==    by 0x504E315: _PyEval_EvalFrameDefault (bytecodes.c:3263)
==59009== 

CPython versions tested on:

3.12

Operating systems tested on:

Linux

[picnixz]

Unfortunately, without a reproducer, it's very hard to help you. Could the issue be with MPI itself? Can you give us at least an input that would lead to this? or tell us what you code does? also, it doesn't mean that running different stuff couldn't be responsible for the issue since PyUnicode_Decode is used for decoding strings, and it can be used from anywhere (so whatever you change may not necessarily change the input to that function)

[abkein]

It turned out, the error has nothing to do with MPI, rather than with json module

I just run this:

kein@aleaf:/tmp/test> valgrind --track-origins=yes python -c "import json"
==11266== Memcheck, a memory error detector
==11266== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==11266== Using Valgrind-3.12.0 and LibVEX; rerun with -h for copyright info
==11266== Command: python -c import\ json
==11266== 
==11266== Conditional jump or move depends on uninitialised value(s)
==11266==    at 0x50CD551: PyUnicode_Decode (unicodeobject.c:3275)
==11266==    by 0x50BEB1E: UnknownInlinedFun (unicodeobject.c:3148)
==11266==    by 0x50BEB1E: UnknownInlinedFun (unicodeobject.c:14515)
==11266==    by 0x50BEB1E: unicode_new (unicodeobject.c.h:1497)
==11266==    by 0x50402E8: UnknownInlinedFun (typeobject.c:1665)
==11266==    by 0x50402E8: _PyObject_MakeTpCall (call.c:240)
==11266==    by 0x5049094: _PyEval_EvalFrameDefault (bytecodes.c:2715)
==11266==    by 0x5042E84: UnknownInlinedFun (pycore_ceval.h:89)
==11266==    by 0x5042E84: UnknownInlinedFun (ceval.c:1683)
==11266==    by 0x5042E84: UnknownInlinedFun (call.c:419)
==11266==    by 0x5042E84: _PyObject_FastCallDictTstate (call.c:133)
==11266==    by 0x5081D58: UnknownInlinedFun (call.c:508)
==11266==    by 0x5081D58: slot_tp_init (typeobject.c:9023)
==11266==    by 0x50403BA: UnknownInlinedFun (typeobject.c:1677)
==11266==    by 0x50403BA: _PyObject_MakeTpCall (call.c:240)
==11266==    by 0x5049094: _PyEval_EvalFrameDefault (bytecodes.c:2715)
==11266==    by 0x511F331: PyEval_EvalCode (ceval.c:578)
==11266==    by 0x513B558: UnknownInlinedFun (bltinmodule.c:1096)
==11266==    by 0x513B558: builtin_exec (bltinmodule.c.h:586)
==11266==    by 0x506522D: cfunction_vectorcall_FASTCALL_KEYWORDS (methodobject.c:438)
==11266==    by 0x504E315: UnknownInlinedFun (call.c:387)
==11266==    by 0x504E315: _PyEval_EvalFrameDefault (bytecodes.c:3263)
==11266==  Uninitialised value was created by a stack allocation
==11266==    at 0x50CD440: PyUnicode_Decode (unicodeobject.c:3234)
==11266== 
==11266== 
==11266== HEAP SUMMARY:
==11266==     in use at exit: 395,628 bytes in 8 blocks
==11266==   total heap usage: 4,079 allocs, 4,071 frees, 20,883,841 bytes allocated
==11266== 
==11266== LEAK SUMMARY:
==11266==    definitely lost: 0 bytes in 0 blocks
==11266==    indirectly lost: 0 bytes in 0 blocks
==11266==      possibly lost: 0 bytes in 0 blocks
==11266==    still reachable: 395,628 bytes in 8 blocks
==11266==         suppressed: 0 bytes in 0 blocks
==11266== Rerun with --leak-check=full to see details of leaked memory
==11266== 
==11266== For counts of detected and suppressed errors, rerun with: -v
==11266== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

[picnixz]

Is it only for import json or is it for any other module? (it could be an import issue, or a json issue) (just asking to help targetting the issue)

[abkein]

Only for json module

Python version: 3.12.6

If it helps, run with -v python option

kein@aleaf:/tmp/test> valgrind --track-origins=yes python -v -c "import json"
==76260== Memcheck, a memory error detector
==76260== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==76260== Using Valgrind-3.12.0 and LibVEX; rerun with -h for copyright info
==76260== Command: python -v -c import\ json
==76260==
import _frozen_importlib # frozen
import _imp # builtin
import '_thread' # <class '_frozen_importlib.BuiltinImporter'>
import '_warnings' # <class '_frozen_importlib.BuiltinImporter'>
import '_weakref' # <class '_frozen_importlib.BuiltinImporter'>
import '_io' # <class '_frozen_importlib.BuiltinImporter'>
import 'marshal' # <class '_frozen_importlib.BuiltinImporter'>
import 'posix' # <class '_frozen_importlib.BuiltinImporter'>
import '_frozen_importlib_external' # <class '_frozen_importlib.FrozenImporter'>
# installing zipimport hook
import 'time' # <class '_frozen_importlib.BuiltinImporter'>
import 'zipimport' # <class '_frozen_importlib.FrozenImporter'>
# installed zipimport hook
# path/to/lib/python3.12/encodings/__pycache__/__init__.cpython-312.pyc matches path/to/lib/python3.12/encodings/__init__.py
# code object from 'path/to/lib/python3.12/encodings/__pycache__/__init__.cpython-312.pyc'
import '_codecs' # <class '_frozen_importlib.BuiltinImporter'>
import 'codecs' # <class '_frozen_importlib.FrozenImporter'>
# path/to/lib/python3.12/encodings/__pycache__/aliases.cpython-312.pyc matches path/to/lib/python3.12/encodings/aliases.py
# code object from 'path/to/lib/python3.12/encodings/__pycache__/aliases.cpython-312.pyc'
import 'encodings.aliases' # <_frozen_importlib_external.SourceFileLoader object at 0x4169880>
import 'encodings' # <_frozen_importlib_external.SourceFileLoader object at 0x4168ec0>
# path/to/lib/python3.12/encodings/__pycache__/utf_8.cpython-312.pyc matches path/to/lib/python3.12/encodings/utf_8.py
# code object from 'path/to/lib/python3.12/encodings/__pycache__/utf_8.cpython-312.pyc'
import 'encodings.utf_8' # <_frozen_importlib_external.SourceFileLoader object at 0x416be00>
import '_signal' # <class '_frozen_importlib.BuiltinImporter'>
import '_abc' # <class '_frozen_importlib.BuiltinImporter'>
import 'abc' # <class '_frozen_importlib.FrozenImporter'>
import 'io' # <class '_frozen_importlib.FrozenImporter'>
import '_stat' # <class '_frozen_importlib.BuiltinImporter'>
import 'stat' # <class '_frozen_importlib.FrozenImporter'>
import '_collections_abc' # <class '_frozen_importlib.FrozenImporter'>
import 'genericpath' # <class '_frozen_importlib.FrozenImporter'>
import 'posixpath' # <class '_frozen_importlib.FrozenImporter'>
import 'os' # <class '_frozen_importlib.FrozenImporter'>
import '_sitebuiltins' # <class '_frozen_importlib.FrozenImporter'>
Processing global site-packages
Adding directory: 'path/to/lib/python3.12/site-packages'
Processing .pth file: 'path/to/lib/python3.12/site-packages/distutils-precedence.pth'
# path/to/lib/python3.12/encodings/__pycache__/utf_8_sig.cpython-312.pyc matches path/to/lib/python3.12/encodings/utf_8_sig.py
# code object from 'path/to/lib/python3.12/encodings/__pycache__/utf_8_sig.cpython-312.pyc'
import 'encodings.utf_8_sig' # <_frozen_importlib_external.SourceFileLoader object at 0x41825d0>
# /mnt/beegfs-storage/scratch/perevoshchikyy/repos/venv_axe/lib/python3.12/site-packages/_distutils_hack/__pycache__/__init__.cpython-312.pyc matches /mnt/beegfs-storage/scratch/perevoshchikyy/repos/venv_axe/lib/python3.12/site-packages/_distutils_hack/__init__.py
# code object from '/mnt/beegfs-storage/scratch/perevoshchikyy/repos/venv_axe/lib/python3.12/site-packages/_distutils_hack/__pycache__/__init__.cpython-312.pyc'
import '_distutils_hack' # <_frozen_importlib_external.SourceFileLoader object at 0x41830e0>
Processing user site-packages
Processing global site-packages
Adding directory: '/mnt/beegfs-storage/scratch/perevoshchikyy/repos/venv_axe/lib/python3.12/site-packages'
Processing .pth file: '/mnt/beegfs-storage/scratch/perevoshchikyy/repos/venv_axe/lib/python3.12/site-packages/distutils-precedence.pth'
import 'site' # <class '_frozen_importlib.FrozenImporter'>
Python 3.12.6 (main, Oct 27 2024, 07:16:01) [GCC 10.2.1 20201202 [revision e563687cf9d3d1278f45aaebd03e0f66531076c9]] on linux
Type "help", "copyright", "credits" or "license" for more information.
# /path/to/lib/python3.12/json/__pycache__/__init__.cpython-312.pyc matches /path/to/lib/python3.12/json/__init__.py
# code object from '/path/to/lib/python3.12/json/__pycache__/__init__.cpython-312.pyc'
# /path/to/lib/python3.12/json/__pycache__/decoder.cpython-312.pyc matches /path/to/lib/python3.12/json/decoder.py
# code object from '/path/to/lib/python3.12/json/__pycache__/decoder.cpython-312.pyc'
# /path/to/lib/python3.12/re/__pycache__/__init__.cpython-312.pyc matches /path/to/lib/python3.12/re/__init__.py
# code object from '/path/to/lib/python3.12/re/__pycache__/__init__.cpython-312.pyc'
# /path/to/lib/python3.12/__pycache__/enum.cpython-312.pyc matches /path/to/lib/python3.12/enum.py
# code object from '/path/to/lib/python3.12/__pycache__/enum.cpython-312.pyc'
# /path/to/lib/python3.12/__pycache__/types.cpython-312.pyc matches /path/to/lib/python3.12/types.py
# code object from '/path/to/lib/python3.12/__pycache__/types.cpython-312.pyc'
import 'types' # <_frozen_importlib_external.SourceFileLoader object at 0x67f3fb0>
# /path/to/lib/python3.12/__pycache__/operator.cpython-312.pyc matches /path/to/lib/python3.12/operator.py
# code object from '/path/to/lib/python3.12/__pycache__/operator.cpython-312.pyc'
import '_operator' # <class '_frozen_importlib.BuiltinImporter'>
import 'operator' # <_frozen_importlib_external.SourceFileLoader object at 0x6808380>
# /path/to/lib/python3.12/__pycache__/functools.cpython-312.pyc matches /path/to/lib/python3.12/functools.py
# code object from '/path/to/lib/python3.12/__pycache__/functools.cpython-312.pyc'
# /path/to/lib/python3.12/collections/__pycache__/__init__.cpython-312.pyc matches /path/to/lib/python3.12/collections/__init__.py
# code object from '/path/to/lib/python3.12/collections/__pycache__/__init__.cpython-312.pyc'
import 'itertools' # <class '_frozen_importlib.BuiltinImporter'>
# /path/to/lib/python3.12/__pycache__/keyword.cpython-312.pyc matches /path/to/lib/python3.12/keyword.py
# code object from '/path/to/lib/python3.12/__pycache__/keyword.cpython-312.pyc'
import 'keyword' # <_frozen_importlib_external.SourceFileLoader object at 0x682baa0>
# /path/to/lib/python3.12/__pycache__/reprlib.cpython-312.pyc matches /path/to/lib/python3.12/reprlib.py
# code object from '/path/to/lib/python3.12/__pycache__/reprlib.cpython-312.pyc'
import 'reprlib' # <_frozen_importlib_external.SourceFileLoader object at 0x6848170>
import '_collections' # <class '_frozen_importlib.BuiltinImporter'>
import 'collections' # <_frozen_importlib_external.SourceFileLoader object at 0x680bd10>
import '_functools' # <class '_frozen_importlib.BuiltinImporter'>
import 'functools' # <_frozen_importlib_external.SourceFileLoader object at 0x68095b0>
import 'enum' # <_frozen_importlib_external.SourceFileLoader object at 0x67f1310>
# /path/to/lib/python3.12/re/__pycache__/_compiler.cpython-312.pyc matches /path/to/lib/python3.12/re/_compiler.py
# code object from '/path/to/lib/python3.12/re/__pycache__/_compiler.cpython-312.pyc'
import '_sre' # <class '_frozen_importlib.BuiltinImporter'>
# /path/to/lib/python3.12/re/__pycache__/_parser.cpython-312.pyc matches /path/to/lib/python3.12/re/_parser.py
# code object from '/path/to/lib/python3.12/re/__pycache__/_parser.cpython-312.pyc'
# /path/to/lib/python3.12/re/__pycache__/_constants.cpython-312.pyc matches /path/to/lib/python3.12/re/_constants.py
# code object from '/path/to/lib/python3.12/re/__pycache__/_constants.cpython-312.pyc'
import 're._constants' # <_frozen_importlib_external.SourceFileLoader object at 0x684ba40>
import 're._parser' # <_frozen_importlib_external.SourceFileLoader object at 0x684a690>
# /path/to/lib/python3.12/re/__pycache__/_casefix.cpython-312.pyc matches /path/to/lib/python3.12/re/_casefix.py
# code object from '/path/to/lib/python3.12/re/__pycache__/_casefix.cpython-312.pyc'
import 're._casefix' # <_frozen_importlib_external.SourceFileLoader object at 0x680a360>
import 're._compiler' # <_frozen_importlib_external.SourceFileLoader object at 0x6848da0>
# /path/to/lib/python3.12/__pycache__/copyreg.cpython-312.pyc matches /path/to/lib/python3.12/copyreg.py
# code object from '/path/to/lib/python3.12/__pycache__/copyreg.cpython-312.pyc'
import 'copyreg' # <_frozen_importlib_external.SourceFileLoader object at 0x687ca70>
import 're' # <_frozen_importlib_external.SourceFileLoader object at 0x67f0620>
# /path/to/lib/python3.12/json/__pycache__/scanner.cpython-312.pyc matches /path/to/lib/python3.12/json/scanner.py
# code object from '/path/to/lib/python3.12/json/__pycache__/scanner.cpython-312.pyc'
# extension module '_json' loaded from '/path/to/lib/python3.12/lib-dynload/_json.cpython-312-x86_64-linux-gnu.so'
# extension module '_json' executed from '/path/to/lib/python3.12/lib-dynload/_json.cpython-312-x86_64-linux-gnu.so'
import '_json' # <_frozen_importlib_external.ExtensionFileLoader object at 0x687d0d0>
import 'json.scanner' # <_frozen_importlib_external.SourceFileLoader object at 0x687ce60>
import 'json.decoder' # <_frozen_importlib_external.SourceFileLoader object at 0x4183d40>
# /path/to/lib/python3.12/json/__pycache__/encoder.cpython-312.pyc matches /path/to/lib/python3.12/json/encoder.py
# code object from '/path/to/lib/python3.12/json/__pycache__/encoder.cpython-312.pyc'
==76260== Conditional jump or move depends on uninitialised value(s)
==76260==    at 0x50CD551: PyUnicode_Decode (unicodeobject.c:3275)
==76260==    by 0x50BEB1E: UnknownInlinedFun (unicodeobject.c:3148)
==76260==    by 0x50BEB1E: UnknownInlinedFun (unicodeobject.c:14515)
==76260==    by 0x50BEB1E: unicode_new (unicodeobject.c.h:1497)
==76260==    by 0x50402E8: UnknownInlinedFun (typeobject.c:1665)
==76260==    by 0x50402E8: _PyObject_MakeTpCall (call.c:240)
==76260==    by 0x5049094: _PyEval_EvalFrameDefault (bytecodes.c:2715)
==76260==    by 0x5042E84: UnknownInlinedFun (pycore_ceval.h:89)
==76260==    by 0x5042E84: UnknownInlinedFun (ceval.c:1683)
==76260==    by 0x5042E84: UnknownInlinedFun (call.c:419)
==76260==    by 0x5042E84: _PyObject_FastCallDictTstate (call.c:133)
==76260==    by 0x5081D58: UnknownInlinedFun (call.c:508)
==76260==    by 0x5081D58: slot_tp_init (typeobject.c:9023)
==76260==    by 0x50403BA: UnknownInlinedFun (typeobject.c:1677)
==76260==    by 0x50403BA: _PyObject_MakeTpCall (call.c:240)
==76260==    by 0x5049094: _PyEval_EvalFrameDefault (bytecodes.c:2715)
==76260==    by 0x511F331: PyEval_EvalCode (ceval.c:578)
==76260==    by 0x513B558: UnknownInlinedFun (bltinmodule.c:1096)
==76260==    by 0x513B558: builtin_exec (bltinmodule.c.h:586)
==76260==    by 0x506522D: cfunction_vectorcall_FASTCALL_KEYWORDS (methodobject.c:438)
==76260==    by 0x504E315: UnknownInlinedFun (call.c:387)
==76260==    by 0x504E315: _PyEval_EvalFrameDefault (bytecodes.c:3263)
==76260==  Uninitialised value was created by a stack allocation
==76260==    at 0x50CD440: PyUnicode_Decode (unicodeobject.c:3234)
==76260==
import 'json.encoder' # <_frozen_importlib_external.SourceFileLoader object at 0x67f0440>
import 'json' # <_frozen_importlib_external.SourceFileLoader object at 0x4182c30>
# clear sys.path_importer_cache
# clear sys.path_hooks
# clear builtins._
# clear sys.path
# clear sys.argv
# clear sys.ps1
# clear sys.ps2
# clear sys.last_exc
# clear sys.last_type
# clear sys.last_value
# clear sys.last_traceback
# clear sys.__interactivehook__
# clear sys.meta_path
# restore sys.stdin
# restore sys.stdout
# restore sys.stderr
# cleanup[2] removing sys
# cleanup[2] removing builtins
# cleanup[2] removing _frozen_importlib
# cleanup[2] removing _imp
# cleanup[2] removing _thread
# cleanup[2] removing _warnings
# cleanup[2] removing _weakref
# cleanup[2] removing _io
# cleanup[2] removing marshal
# cleanup[2] removing posix
# cleanup[2] removing _frozen_importlib_external
# cleanup[2] removing time
# cleanup[2] removing zipimport
# destroy zipimport
# cleanup[2] removing _codecs
# cleanup[2] removing codecs
# cleanup[2] removing encodings.aliases
# cleanup[2] removing encodings
# destroy encodings
# cleanup[2] removing encodings.utf_8
# cleanup[2] removing _signal
# cleanup[2] removing _abc
# cleanup[2] removing abc
# cleanup[2] removing io
# cleanup[2] removing __main__
# destroy __main__
# cleanup[2] removing _stat
# cleanup[2] removing stat
# cleanup[2] removing _collections_abc
# cleanup[2] removing genericpath
# cleanup[2] removing posixpath
# cleanup[2] removing os.path
# cleanup[2] removing os
# cleanup[2] removing _sitebuiltins
# cleanup[2] removing encodings.utf_8_sig
# cleanup[2] removing _distutils_hack
# destroy _distutils_hack
# cleanup[2] removing site
# destroy site
# cleanup[2] removing types
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# cleanup[2] removing _operator
# cleanup[2] removing operator
# destroy operator
# cleanup[2] removing itertools
# cleanup[2] removing keyword
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# cleanup[2] removing reprlib
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# cleanup[2] removing _collections
# cleanup[2] removing collections
# destroy collections
# cleanup[2] removing _functools
# cleanup[2] removing functools
# cleanup[2] removing enum
# cleanup[2] removing _sre
# cleanup[2] removing re._constants
# cleanup[2] removing re._parser
# cleanup[2] removing re._casefix
# cleanup[2] removing re._compiler
# cleanup[2] removing copyreg
# cleanup[2] removing re
# cleanup[2] removing _json
# cleanup[2] removing json.scanner
# cleanup[2] removing json.decoder
# cleanup[2] removing json.encoder
# cleanup[2] removing json
# destroy json
# destroy time
# destroy _signal
# destroy _sitebuiltins
# destroy io
# destroy abc
# destroy posixpath
# destroy _stat
# destroy genericpath
# destroy stat
# destroy os
# destroy json.decoder
# destroy json.encoder
# destroy json.scanner
# destroy enum
# destroy re._constants
# destroy re._casefix
# destroy re._compiler
# destroy functools
# destroy copyreg
# destroy _abc
# destroy _collections_abc
# destroy _operator
# destroy itertools
# destroy _collections
# destroy _functools
# destroy re._parser
# destroy _sre
# destroy re
# destroy _json
# cleanup[3] wiping encodings.utf_8_sig
# cleanup[3] wiping encodings.utf_8
# cleanup[3] wiping encodings.aliases
# cleanup[3] wiping codecs
# cleanup[3] wiping _codecs
# cleanup[3] wiping _frozen_importlib_external
# cleanup[3] wiping posix
# cleanup[3] wiping marshal
# destroy marshal
# cleanup[3] wiping _io
# cleanup[3] wiping _weakref
# cleanup[3] wiping _warnings
# cleanup[3] wiping _thread
# cleanup[3] wiping _imp
# cleanup[3] wiping _frozen_importlib
# destroy _warnings
# destroy _weakref
# destroy _frozen_importlib_external
# destroy _imp
# cleanup[3] wiping sys
# cleanup[3] wiping builtins
# destroy sys.monitoring
# destroy _thread
# destroy _io
# destroy posix
# clear sys.meta_path
# clear sys.modules
# destroy _frozen_importlib
# destroy codecs
# destroy sys
# destroy encodings.aliases
# destroy encodings.utf_8
# destroy encodings.utf_8_sig
# destroy _codecs
# destroy builtins
# clear sys.audit hooks
==76260==
==76260== HEAP SUMMARY:
==76260==     in use at exit: 395,628 bytes in 8 blocks
==76260==   total heap usage: 4,089 allocs, 4,081 frees, 20,884,045 bytes allocated
==76260==
==76260== LEAK SUMMARY:
==76260==    definitely lost: 0 bytes in 0 blocks
==76260==    indirectly lost: 0 bytes in 0 blocks
==76260==      possibly lost: 0 bytes in 0 blocks
==76260==    still reachable: 395,628 bytes in 8 blocks
==76260==         suppressed: 0 bytes in 0 blocks
==76260== Rerun with --leak-check=full to see details of leaked memory
==76260==
==76260== For counts of detected and suppressed errors, rerun with: -v
==76260== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

[picnixz]

It's a bit late here but I'll try to see more tomorrow and investigate (it might also be a false positive) cc @serhiy-storchaka for JSON-related stuff

[picnixz]

Sorry but I didn't have time to check this today and won't have any for the next two weeks. So I'll let someone else investigate this.

[serhiy-storchaka]

It seems that it complains for strcmp(lower, "ascii") or strcmp(lower, "us_ascii"). lower is a reference to the buflower array allocated on stack. buflower is initialized in _Py_normalize_encoding(). If _Py_normalize_encoding() returns 1, buflower is always null-terminated. It is only not null-terminated when _Py_normalize_encoding() returns 0, but then that code should not be executed.

So I do not understand why valgrind complains. It can only be possible if there is a bug in strcmp() or the code generation. Or maybe hardware error. I cannot reproduce that issue on my computer (I tried to build Python 3.12.6 with different options).