[issue42057] pytest case which catch exceptions become segfault

[Inada Naoki]

Inada Naoki  added the comment:

I confirmed fix42057.patch fix the assertion failure. But I don't know where 
and how to write test yet.

--
keywords: +patch
Added file: https://bugs.python.org/file49527/fix42057.patch

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[issue42057] pytest case which catch exceptions become segfault

[Inada Naoki]

Inada Naoki  added the comment:

I confirmed the issue. The simple version of the reproducer is:

```
def callee():
raise Exception

def caller():
try:
callee()
except Exception or Exception:
pass

caller()
```

I can see assertion failure consisntently, when I use python --with-pydebug.

It seems peephole bug. Without peephole:

```
  7 >>   12 DUP_TOP
 14 LOAD_GLOBAL  1 (Exception)
 16 JUMP_IF_TRUE_OR_POP 20
 18 LOAD_GLOBAL  1 (Exception)
>>   20 JUMP_IF_NOT_EXC_MATCH32
 22 POP_TOP
 24 POP_TOP
 26 POP_TOP

  8  28 POP_EXCEPT
 30 JUMP_FORWARD 2 (to 34)
>>   32 RERAISE
>>   34 LOAD_CONST   0 (None)
 36 RETURN_VALUE
```

And with peephole:

```
  7 >>   12 DUP_TOP
 14 LOAD_GLOBAL  1 (Exception)
 16 POP_JUMP_IF_TRUE22
 18 LOAD_GLOBAL  1 (Exception)
 20 JUMP_IF_NOT_EXC_MATCH32
>>   22 POP_TOP
 24 POP_TOP
 26 POP_TOP

  8  28 POP_EXCEPT
 30 JUMP_FORWARD 2 (to 34)
>>   32 RERAISE
>>   34 LOAD_CONST   0 (None)
 36 RETURN_VALUE
```

JUMP_IF_TRUE_OR_POP is converted into POP_JUMP_IF_TRUE. Exception is popped 
although JUMP_IF_NOT_EXC_MATCH needs it.

--
nosy: +methane

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[issue42057] pytest case which catch exceptions become segfault

[Mark Shannon]

Mark Shannon  added the comment:

The test example has no reference to pytest in it.

How are you running it?
Can you produce a segmentation fault when run without pytest?

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[issue42057] pytest case which catch exceptions become segfault

[Filipe Laíns]

Change by Filipe Laíns :


--
nosy: +FFY00

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[issue42057] pytest case which catch exceptions become segfault

[Hiroshi Miura]

Hiroshi Miura  added the comment:

A test code does not always reproduce the issue. Please try it in several times.

It seems to be happened when multiple threads try execute a same function which 
produces an exception, and both callers try to catch the exception at the same 
time.

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[issue42057] pytest case which catch exceptions become segfault

[Hiroshi Miura]

Hiroshi Miura  added the comment:

FYI: A following commit fixes the issue in 3.10 development branch.

6e8128f02e ("bpo-41323: Perform 'peephole' optimizations directly on the CFG. 
(GH-21517)", 2020-07-30)

--
nosy: +Mark.Shannon

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[issue42057] pytest case which catch exceptions become segfault

[Hiroshi Miura]

Hiroshi Miura  added the comment:

Here is a result of running pytest on python 3.9.0 with gdb.

 test session starts 

platform linux -- Python 3.9.0, pytest-4.6.9, py-1.8.1, pluggy-0.13.0
rootdir: /home/miurahr/Projects/cpython
collected 2 items

test_main.py .
Program received signal SIGSEGV, Segmentation fault.
PyException_GetContext (self=self@entry=) 
at ../Objects/exceptions.c:351
warning: Source file is more recent than executable.
351 Py_XINCREF(context);

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[issue42057] pytest case which catch exceptions become segfault

[Hiroshi Miura]

Change by Hiroshi Miura :


Added file: https://bugs.python.org/file49523/gdb_backtrace.txt

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[issue42057] pytest case which catch exceptions become segfault

[Hiroshi Miura]

Change by Hiroshi Miura :


Added file: https://bugs.python.org/file49522/py_stacktrace.txt

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[issue42057] pytest case which catch exceptions become segfault

[Hiroshi Miura]

New submission from Hiroshi Miura :

I've observed that pytest becomes segmentation fault on python 3.9.0 with 
attached case.

I've tested the case with several python versions;
  python 3.9.0a2 - good
  python 3.9.0a3, 3.9.0-final - bad
  python 3.10.0a1 - good

- OS: Mint Linux 20, Linux kernel 5.8.14
- Attachments:
* test_main.py  - pytest test case to reproduce
* py_stacktrace.txt - pytest result which become segmentation fault
* gdb_backtrace.txt - gdb backtrace

So I've bisected and  a result is as follows;

9af0e47b1705457bb6b327c197f2ec5737a1d8f6 is the first bad commit
commit 9af0e47b1705457bb6b327c197f2ec5737a1d8f6
Author: Mark Shannon 
Date:   Tue Jan 14 10:12:45 2020 +

bpo-39156: Break up COMPARE_OP into four logically distinct opcodes. 
(GH-17754)

Break up COMPARE_OP into four logically distinct opcodes:
* COMPARE_OP for rich comparisons
* IS_OP for 'is' and 'is not' tests
* CONTAINS_OP for 'in' and 'is not' tests
* JUMP_IF_NOT_EXC_MATCH for checking exceptions in 'try-except' statements.

 Doc/library/dis.rst|   21 +
 Include/opcode.h   |8 +-
 Lib/importlib/_bootstrap_external.py   |3 +-
 Lib/opcode.py  |7 +-
 Lib/test/test_dis.py   |  141 +-
 Lib/test/test_peepholer.py |   12 +-
 Lib/test/test_positional_only_arg.py   |6 +-
 .../2019-12-30-10-53-59.bpo-39156.veT-CB.rst   |9 +
 PC/launcher.c  |3 +-
 Python/ceval.c |  137 +-
 Python/compile.c   |   71 +-
 Python/importlib.h | 2922 +++--
 Python/importlib_external.h| 4560 ++--
 Python/importlib_zipimport.h   | 1831 
 Python/opcode_targets.h|6 +-
 Python/peephole.c  |6 +-
 Tools/scripts/generate_opcode_h.py |5 -
 17 files changed, 4901 insertions(+), 4847 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Core and 
Builtins/2019-12-30-10-53-59.bpo-39156.veT-CB.rst

--
components: Interpreter Core
files: test_main.py
messages: 378796
nosy: miurahr
priority: normal
severity: normal
status: open
title: pytest case which catch  exceptions become segfault
type: crash
versions: Python 3.9
Added file: https://bugs.python.org/file49521/test_main.py

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