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Commit 20d30ba

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gh-92898: Enhance _testcppext test on cast to PyObject* (#93111)
* Add StrongRef class. * Rename and reformat functions of the _Py_CAST() implementation.
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‎Include/pyport.h

Copy file name to clipboardExpand all lines: Include/pyport.h
+23-25Lines changed: 23 additions & 25 deletions
Original file line numberDiff line numberDiff line change
@@ -22,35 +22,33 @@
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// _Py_CAST(PyObject*, op) can convert a "const PyObject*" to
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// "PyObject*".
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//
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// The type argument must not be constant. For example, in C++,
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// _Py_CAST(const PyObject*, expr) fails with a compiler error.
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// The type argument must not be a constant type.
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#ifdef __cplusplus
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# define _Py_STATIC_CAST(type, expr) static_cast<type>(expr)
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extern "C++" {
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namespace {
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template <typename type, typename expr_type>
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inline type _Py_reinterpret_cast_impl(expr_type *expr) {
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return reinterpret_cast<type>(expr);
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}
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template <typename type, typename expr_type>
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inline type _Py_reinterpret_cast_impl(expr_type const *expr) {
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return reinterpret_cast<type>(const_cast<expr_type *>(expr));
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}
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template <typename type, typename expr_type>
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inline type _Py_reinterpret_cast_impl(expr_type &expr) {
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return static_cast<type>(expr);
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}
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template <typename type, typename expr_type>
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inline type _Py_reinterpret_cast_impl(expr_type const &expr) {
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return static_cast<type>(const_cast<expr_type &>(expr));
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}
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} // namespace
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namespace {
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template <typename type, typename expr_type>
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inline type _Py_CAST_impl(expr_type *expr) {
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return reinterpret_cast<type>(expr);
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}
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template <typename type, typename expr_type>
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inline type _Py_CAST_impl(expr_type const *expr) {
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return reinterpret_cast<type>(const_cast<expr_type *>(expr));
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}
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template <typename type, typename expr_type>
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inline type _Py_CAST_impl(expr_type &expr) {
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return static_cast<type>(expr);
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}
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template <typename type, typename expr_type>
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inline type _Py_CAST_impl(expr_type const &expr) {
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return static_cast<type>(const_cast<expr_type &>(expr));
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}
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}
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}
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# define _Py_CAST(type, expr) _Py_reinterpret_cast_impl<type>(expr)
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# define _Py_CAST(type, expr) _Py_CAST_impl<type>(expr)
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#else
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# define _Py_STATIC_CAST(type, expr) ((type)(expr))

‎Lib/test/_testcppext.cpp

Copy file name to clipboardExpand all lines: Lib/test/_testcppext.cpp
+31-11Lines changed: 31 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -23,13 +23,35 @@ _testcppext_add(PyObject *Py_UNUSED(module), PyObject *args)
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}
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// Class to test operator casting an object to PyObject*
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class StrongRef
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{
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public:
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StrongRef(PyObject *obj) : m_obj(obj) {
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Py_INCREF(this->m_obj);
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}
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~StrongRef() {
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Py_DECREF(this->m_obj);
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}
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// Cast to PyObject*: get a borrowed reference
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inline operator PyObject*() const { return this->m_obj; }
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private:
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PyObject *m_obj; // Strong reference
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};
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static PyObject *
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test_api_casts(PyObject *Py_UNUSED(module), PyObject *Py_UNUSED(args))
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{
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PyObject *obj = Py_BuildValue("(ii)", 1, 2);
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if (obj == nullptr) {
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return nullptr;
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}
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Py_ssize_t refcnt = Py_REFCNT(obj);
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assert(refcnt >= 1);
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// gh-92138: For backward compatibility, functions of Python C API accepts
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// "const PyObject*". Check that using it does not emit C++ compiler
@@ -38,22 +60,20 @@ test_api_casts(PyObject *Py_UNUSED(module), PyObject *Py_UNUSED(args))
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Py_INCREF(const_obj);
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Py_DECREF(const_obj);
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PyTypeObject *type = Py_TYPE(const_obj);
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assert(Py_REFCNT(const_obj) >= 1);
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struct PyObjectProxy {
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PyObject* obj;
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operator PyObject *() { return obj; }
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} proxy_obj = { obj };
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Py_INCREF(proxy_obj);
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Py_DECREF(proxy_obj);
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assert(Py_REFCNT(proxy_obj) >= 1);
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assert(Py_REFCNT(const_obj) == refcnt);
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assert(type == &PyTuple_Type);
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assert(PyTuple_GET_SIZE(const_obj) == 2);
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PyObject *one = PyTuple_GET_ITEM(const_obj, 0);
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assert(PyLong_AsLong(one) == 1);
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// gh-92898: StrongRef doesn't inherit from PyObject but has an operator to
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// cast to PyObject*.
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StrongRef strong_ref(obj);
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assert(Py_TYPE(strong_ref) == &PyTuple_Type);
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assert(Py_REFCNT(strong_ref) == (refcnt + 1));
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Py_INCREF(strong_ref);
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Py_DECREF(strong_ref);
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Py_DECREF(obj);
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Py_RETURN_NONE;
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}
+2Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,2 @@
1+
Fix C++ compiler warnings when casting function arguments to ``PyObject*``.
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Patch by Serge Guelton.

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