[New-bugs-announce] [issue46697] _ctypes_simple_instance returns inverted logic

[hydroflask]

New submission from hydroflask <hydroflask at yqxmail.com>:

`_ctypes_simple_instance` in _ctypes.c returns the opposite logic of what its documentation claims. It is supposed to return true when the argument (a type object) is a direct subclass of `Simple_Type` (`_SimpleCData` in Python code). However it returns false instead.

No bugs have manifested from this because all of the call sites ( `callproc.c::GetResult`, `callbacks.c::_CallPythonObject`,_`ctypes.c::PyCData_get`, `_ctypes.c::Simple_from_outparm`) invert the return value of this function. The last example, `ctypes.c::Simple_from_outparm` only calls `Simple_get_value()` when `_ctypes_simple_instance` returns false, which makes sense because otherwise the invocation of `_ctypes.c::Simple_from_outparm()` could trigger an assertion error.

This is not just simply an issue of inverted logic because the logic isn't inverted in all cases. In `_ctypes_simple_instance` in the case when `PyCSimpleTypeObject_Check(type)` returns false, if this were supposed to be perfect inverted logic then the whole routine would return 1 (True) not 0. Fortunately, due to the way the code is structured, I don't think there is a case when `PyCSimpleTypeObject_Check(type)` returns false so the incorrect case where it returns a constant 0 is effectively dead code.

I have compiled a version of Python with the attached patch and run "make test" with no issues.

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components: ctypes
files: _ctypes_simple_instance_inverted.patch
keywords: patch
messages: 412947
nosy: hydroflask
priority: normal
severity: normal
status: open
title: _ctypes_simple_instance returns inverted logic
type: enhancement
versions: Python 3.10, Python 3.11, Python 3.7, Python 3.8, Python 3.9
Added file: https://bugs.python.org/file50612/_ctypes_simple_instance_inverted.patch

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<https://bugs.python.org/issue46697>
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