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Revert "gh-98724: Fix Py_CLEAR() macro side effects" (#99737)

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Revert "gh-98724: Fix Py_CLEAR() macro side effects (#99100)"

This reverts commit c03e05c2e7.
This commit is contained in:
Victor Stinner 2022-11-24 22:17:33 +01:00 • committed by GitHub
parent 0da728387c
commit 3a803bcaac
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5 changed files with 29 additions and 172 deletions
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44
Include/cpython/object.h
View file

@ -305,41 +305,37 @@ _PyObject_GenericSetAttrWithDict(PyObject *, PyObject *,
PyAPI_FUNC(PyObject *) _PyObject_FunctionStr(PyObject *);
/* Safely decref `dst` and set `dst` to `src`.
/* Safely decref `op` and set `op` to `op2`.
*
* As in case of Py_CLEAR "the obvious" code can be deadly:
*
* Py_DECREF(dst);
* dst = src;
* Py_DECREF(op);
* op = op2;
*
* The safe way is:
*
* Py_SETREF(dst, src);
* Py_SETREF(op, op2);
*
* That arranges to set `dst` to `src` _before_ decref'ing, so that any code
* triggered as a side-effect of `dst` getting torn down no longer believes
* `dst` points to a valid object.
* That arranges to set `op` to `op2` _before_ decref'ing, so that any code
* triggered as a side-effect of `op` getting torn down no longer believes
* `op` points to a valid object.
*
* gh-98724: Use the _tmp_dst_ptr variable to evaluate the 'dst' macro argument
* exactly once, to prevent the duplication of side effects in this macro.
* Py_XSETREF is a variant of Py_SETREF that uses Py_XDECREF instead of
* Py_DECREF.
*/
#define Py_SETREF(dst, src) \
do { \
PyObject **_tmp_dst_ptr = _Py_CAST(PyObject**, &(dst)); \
PyObject *_tmp_dst = (*_tmp_dst_ptr); \
*_tmp_dst_ptr = _PyObject_CAST(src); \
Py_DECREF(_tmp_dst); \
#define Py_SETREF(op, op2) \
do { \
PyObject *_py_tmp = _PyObject_CAST(op); \
(op) = (op2); \
Py_DECREF(_py_tmp); \
} while (0)
/* Py_XSETREF() is a variant of Py_SETREF() that uses Py_XDECREF() instead of
* Py_DECREF().
*/
#define Py_XSETREF(dst, src) \
do { \
PyObject **_tmp_dst_ptr = _Py_CAST(PyObject**, &(dst)); \
PyObject *_tmp_dst = (*_tmp_dst_ptr); \
*_tmp_dst_ptr = _PyObject_CAST(src); \
Py_XDECREF(_tmp_dst); \
#define Py_XSETREF(op, op2) \
do { \
PyObject *_py_tmp = _PyObject_CAST(op); \
(op) = (op2); \
Py_XDECREF(_py_tmp); \
} while (0)

19
Include/object.h
View file

@ -598,21 +598,16 @@ static inline void Py_DECREF(PyObject *op)
* one of those can't cause problems -- but in part that relies on that
* Python integers aren't currently weakly referencable. Best practice is
* to use Py_CLEAR() even if you can't think of a reason for why you need to.
*
* gh-98724: Use the _py_tmp_ptr variable to evaluate the macro argument
* exactly once, to prevent the duplication of side effects in this macro.
*/
#define Py_CLEAR(op) \
do { \
PyObject **_py_tmp_ptr = _Py_CAST(PyObject**, &(op)); \
if (*_py_tmp_ptr != NULL) { \
PyObject* _py_tmp = (*_py_tmp_ptr); \
*_py_tmp_ptr = NULL; \
Py_DECREF(_py_tmp); \
} \
#define Py_CLEAR(op) \
do { \
PyObject *_py_tmp = _PyObject_CAST(op); \
if (_py_tmp != NULL) { \
(op) = NULL; \
Py_DECREF(_py_tmp); \
} \
} while (0)
/* Function to use in case the object pointer can be NULL: */
static inline void Py_XINCREF(PyObject *op)
{