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Python3.7 crash in PyCFunction_New due to broken _PyObject_GC_TRACK #79589
Description
| BPO | 35408 |
|---|---|
| Nosy | @ncoghlan, @vstinner, @ericsnowcurrently |
| Files |
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
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GitHub fields:
assignee = None
closed_at = <Date 2018-12-04.14:29:58.186>
created_at = <Date 2018-12-04.12:35:18.331>
labels = ['interpreter-core', '3.7', 'invalid', 'type-crash']
title = 'Python3.7 crash in PyCFunction_New due to broken _PyObject_GC_TRACK'
updated_at = <Date 2018-12-05.14:07:25.296>
user = 'https://bugs.python.org/etejedor'bugs.python.org fields:
activity = <Date 2018-12-05.14:07:25.296>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2018-12-04.14:29:58.186>
closer = 'vstinner'
components = ['Interpreter Core']
creation = <Date 2018-12-04.12:35:18.331>
creator = 'etejedor'
dependencies = []
files = ['47971']
hgrepos = []
issue_num = 35408
keywords = []
message_count = 5.0
messages = ['331040', '331047', '331048', '331111', '331113']
nosy_count = 4.0
nosy_names = ['ncoghlan', 'vstinner', 'eric.snow', 'etejedor']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue35408'
versions = ['Python 3.7']
Activity
etejedor commentedon Dec 4, 2018
Attached is a reproducer that calls PyCFunction_New. The reproducer runs normally with Python 3.6.5, but it crashes with Python 3.7.1. The reason seems to be that the _PyObject_GC_TRACK macro ends up being called and it is broken in Python3.7.
A fix for that macro seems to have been committed to master:
#10507
vstinner commentedon Dec 4, 2018
It's unrelated. Your must not use the Python API before Python is initialized. If you modify your code like that, it works as expected:
PyMethodDef methoddef_ = {
const_cast< char* >( "myfun" ),
(PyCFunction) myfun,
METH_O,
NULL
};
I don't think that it's a regression.
Python initialization is now well documented:
https://docs.python.org/dev/c-api/init.html
The documentation starts with:
"In an application embedding Python, the Py_Initialize() function must be called before using any other Python/C API functions; with the exception of a few functions and the global configuration variables."
PyCFunction_New() is an example of function of the Python C API.
vstinner commentedon Dec 4, 2018
I close the issue as "not a bug".
Even if the code "worked" in Python 3.6, it worked because of a mistake :-)
etejedor commentedon Dec 5, 2018
Hi Victor,
Thank you for clarifying.
If the call to PyCFunction_New is done from a C extension module, is it also necessary to call Py_Initialize()?
vstinner commentedon Dec 5, 2018
Py_Initialize() must always be called first.