New submission from Sebastian Berg :
Starting here, but there could be Cython interaction or something else in
theory. But, when running the following:
* Python 3.10.1 (not 3.9.9, debug version or not)
* Setting a tracing function (not setting a trace-function will fix the issue)
* Running Cython (maybe also C code) calling back into Python (the best I can
tell)
It can happen that module globals in the called funtions scope seem to be
modified. Oddly enough to a value used in the locals of that function?!
The pandas issue:
https://github.com/pandas-dev/pandas/issues/41935
has a reproducer (sorry that it takes NumPy and pandas for now). I will paste
it at the end here also.
I can find that the value is modified by the time the `trace` function is
called. No other "trace" triggers are processed before in this example (Cython
calls other functions in NumPy, but all of those are C implemented, so I guess
that is why).
The function in question (unlike all?) should further be called with
`__Pyx_PyFunction_FastCall`, so that is probably an important data point:
Fastcall protocol seems involved.
(Reproducible using NumPy 1.21.5 and Pandas 1.3.5, but except maybe pandas due
to the Cython version, I don't expect version dependency.)
The output of the script is very brief:
Something happened here, `np.core.numeric.dtype IS np.dtype`
call None
The full reproducer script is:
import sys
import numpy as np
import pandas as pd
from numpy.core import numeric
stop = False
def trace(frame, event, arg):
global stop
if stop:
return None
if np.core.numeric.dtype is not np.dtype:
print("Something happened here, `np.core.numeric.dtype IS np.dtype`")
print(frame, event, arg)
stop = True
else:
print(frame, event, arg)
return trace
sys.settrace(trace)
pd._libs.lib.maybe_convert_objects(np.array([None], dtype=object))
For completeness, the Cython code calling the NumPy function in question, is
(likley, there is more, this is Cython, I just cut it out a bit :)):
#if CYTHON_FAST_PYCALL
if (PyFunction_Check(__pyx_t_5)) {
PyObject *__pyx_temp[3] = {__pyx_t_2, __pyx_t_6, Py_False};
__pyx_t_15 = __Pyx_PyFunction_FastCall(__pyx_t_5, __pyx_temp+1-__pyx_t_8,
2+__pyx_t_8); if (unlikely(!__pyx_t_15)) __PYX_ERR(0, 2441, __pyx_L1_error)
__Pyx_XDECREF(__pyx_t_2); __pyx_t_2 = 0;
__Pyx_GOTREF(__pyx_t_15);
__Pyx_DECREF(__pyx_t_6); __pyx_t_6 = 0;
} else
#endif
--
components: Interpreter Core
messages: 411082
nosy: seberg
priority: normal
severity: normal
status: open
title: Possibly bad interaction with tracing and cython?
type: crash
versions: Python 3.10
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