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gh-92135: Fix _Py_reinterpret_cast() for const (#92138)

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Fix C++ compiler warnings on cast macros, like _PyObject_CAST(), when
casting a constant expression to a non constant type: use
const_cast<> in C++.

* In C++, Py_SAFE_DOWNCAST() now uses static_cast<> rather than
  reinterpret_cast<>.
* Add tests to the _testcppext C++ extension.
* test_cppext no longer captures stdout in verbose mode.
This commit is contained in:
Victor Stinner 2022-05-02 17:07:00 +02:00 • committed by GitHub
parent b11243e85e
commit 031397063e
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5 changed files with 62 additions and 14 deletions
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31
Lib/test/_testcppext.cpp
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@ -1,6 +1,9 @@
// gh-91321: Very basic C++ test extension to check that the Python C API is
// compatible with C++ and does not emit C++ compiler warnings.
// Always enable assertions
#undef NDEBUG
#include "Python.h"
PyDoc_STRVAR(_testcppext_add_doc,
@ -20,8 +23,36 @@ _testcppext_add(PyObject *Py_UNUSED(module), PyObject *args)
}
static PyObject *
test_api_casts(PyObject *Py_UNUSED(module), PyObject *Py_UNUSED(args))
{
PyObject *obj = Py_BuildValue("(ii)", 1, 2);
if (obj == nullptr) {
return nullptr;
}
// gh-92138: For backward compatibility, functions of Python C API accepts
// "const PyObject*". Check that using it does not emit C++ compiler
// warnings.
const PyObject *const_obj = obj;
Py_INCREF(const_obj);
Py_DECREF(const_obj);
PyTypeObject *type = Py_TYPE(const_obj);
assert(Py_REFCNT(const_obj) >= 1);
assert(type == &PyTuple_Type);
assert(PyTuple_GET_SIZE(const_obj) == 2);
PyObject *one = PyTuple_GET_ITEM(const_obj, 0);
assert(PyLong_AsLong(one) == 1);
Py_DECREF(obj);
Py_RETURN_NONE;
}
static PyMethodDef _testcppext_methods[] = {
{"add", _testcppext_add, METH_VARARGS, _testcppext_add_doc},
{"test_api_casts", test_api_casts, METH_NOARGS, NULL},
{nullptr, nullptr, 0, nullptr} /* sentinel */
};