Repository navigation
Reference leak when failing to raise from an exception cause #140530
Description
Bug report
Bug description:
import unittest
class TestRaise(unittest.TestCase):
def test_class_cause_nonexception_result(self):
class ConstructsNone(BaseException):
def __new__(*args, **kwargs):
return 'A'*1000
try:
raise IndexError from ConstructsNone
except Exception:
pass
if __name__ == "__main__":
unittest.main()=================================================================
==1055698==ERROR: LeakSanitizer: detected memory leaks
Direct leak of 1041 byte(s) in 1 object(s) allocated from:
#0 0x7dd09269b9c7 in malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:69
#1 0x599b8469b90e in PyUnicode_New ../Objects/unicodeobject.c:1358
#2 0x599b846d8ad8 in PyUnicode_New ../Objects/unicodeobject.c:1307
#3 0x599b846d8ad8 in unicode_repeat ../Objects/unicodeobject.c:12640
#4 0x599b846d8ad8 in unicode_repeat ../Objects/unicodeobject.c:12621
#5 0x599b8488cdff in const_folding_safe_multiply ../Python/flowgraph.c:1727
#6 0x599b8488cdff in eval_const_binop ../Python/flowgraph.c:1795
#7 0x599b8488cdff in fold_const_binop ../Python/flowgraph.c:1867
#8 0x599b8488cdff in optimize_basic_block ../Python/flowgraph.c:2489
#9 0x599b8488fe2d in optimize_cfg ../Python/flowgraph.c:2543
#10 0x599b8488fe2d in _PyCfg_OptimizeCodeUnit ../Python/flowgraph.c:3655
#11 0x599b84851cd9 in optimize_and_assemble_code_unit ../Python/compile.c:1432
#12 0x599b84851cd9 in _PyCompile_OptimizeAndAssemble ../Python/compile.c:1474
#13 0x599b848478ac in codegen_function_body ../Python/codegen.c:1388
#14 0x599b848478ac in codegen_function ../Python/codegen.c:1480
#15 0x599b84839bf3 in codegen_visit_stmt ../Python/codegen.c:3095
#16 0x599b8483edd6 in codegen_body ../Python/codegen.c:911
#17 0x599b84840f42 in codegen_class_body ../Python/codegen.c:1569
#18 0x599b84840f42 in codegen_class ../Python/codegen.c:1662
#19 0x599b84839bc9 in codegen_visit_stmt ../Python/codegen.c:3008
#20 0x599b8484786a in codegen_function_body ../Python/codegen.c:1382
#21 0x599b8484786a in codegen_function ../Python/codegen.c:1480
#22 0x599b84839bf3 in codegen_visit_stmt ../Python/codegen.c:3095
#23 0x599b8483edd6 in codegen_body ../Python/codegen.c:911
#24 0x599b84840f42 in codegen_class_body ../Python/codegen.c:1569
#25 0x599b84840f42 in codegen_class ../Python/codegen.c:1662
#26 0x599b84839bc9 in codegen_visit_stmt ../Python/codegen.c:3008
#27 0x599b8483edd6 in codegen_body ../Python/codegen.c:911
#28 0x599b8484a094 in _PyCodegen_Module ../Python/codegen.c:874
#29 0x599b8484bd18 in compiler_codegen ../Python/compile.c:835
#30 0x599b84852481 in compiler_mod ../Python/compile.c:856
#31 0x599b84852481 in _PyAST_Compile ../Python/compile.c:1487
#32 0x599b84954e1c in run_mod ../Python/pythonrun.c:1411
#33 0x599b84959977 in pyrun_file ../Python/pythonrun.c:1293
#34 0x599b84959977 in _PyRun_SimpleFileObject ../Python/pythonrun.c:521
#35 0x599b8495a49c in _PyRun_AnyFileObject ../Python/pythonrun.c:81
#36 0x599b849cd7fc in pymain_run_file_obj ../Modules/main.c:410
#37 0x599b849cd7fc in pymain_run_file ../Modules/main.c:429
#38 0x599b849cd7fc in pymain_run_python ../Modules/main.c:691
#39 0x599b849cf0de in Py_RunMain ../Modules/main.c:772
#40 0x599b849cf0de in pymain_main ../Modules/main.c:802
#41 0x599b849cf0de in Py_BytesMain ../Modules/main.c:826
#42 0x7dd0922cd1c9 (/lib/x86_64-linux-gnu/libc.so.6+0x2a1c9) (BuildId: 282c2c16e7b6600b0b22ea0c99010d2795752b5f)
#43 0x7dd0922cd28a in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2a28a) (BuildId: 282c2c16e7b6600b0b22ea0c99010d2795752b5f)
#44 0x599b84369524 in _start (/home/fuzz/WorkSpace/flowfusion-cpython/cpython-normal/build/python+0x20e524) (BuildId: b922665a0e7afc8ee52df7c3eac25a643025109e)
SUMMARY: AddressSanitizer: 1041 byte(s) leaked in 1 allocation(s).
CPython versions tested on:
CPython main branch
Operating systems tested on:
Linux
Activity
StanFromIreland commentedon Oct 24, 2025
I will look into this.
[-]memory leak const_folding_safe_multiply[/-][+]Reference leak when raising from a non-exception[/+]picnixz commentedon Nov 2, 2025
Simpler reproducer:
[-]Reference leak when raising from a non-exception[/-][+]Reference leak when raising from a non-exception constructed as a string[/+][-]Reference leak when raising from a non-exception constructed as a string[/-][+]Reference leak when raising from a non-exception with constant folded return in `__new__`[/+]picnixz commentedon Nov 2, 2025
The directly returned
__new__value that is constant folded is not cleared upon error. This happens withreturn (10,) * 2but also withx = "A" * 1000; return xpicnixz commentedon Nov 2, 2025
I found the issue. PR incoming.
[-]Reference leak when raising from a non-exception with constant folded return in `__new__`[/-][+]Reference leak when raising from a non-exception cause[/+][-]Reference leak when raising from a non-exception cause[/-][+]Reference leak when raising from a non-exception cause inheriting from BaseException[/+][-]Reference leak when raising from a non-exception cause inheriting from BaseException[/-][+]Reference leak when failing to raise from an exception cause[/+]gh-140530: fix a reference leak in an error path for `raise exc from …
pythongh-140530: fix a reference leak in an error path for `raise exc…
[3.13] gh-140530: fix a reference leak in an error path for `raise ex…
[3.14] gh-140530: fix a reference leak in an error path for `raise ex…
picnixz commentedon Nov 9, 2025
Thanks for the report!
pythongh-140530: fix a reference leak in an error path for `raise exc…