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| author | Victor Stinner <vstinner@python.org> | 2022-11-09 13:06:36 (GMT) |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2022-11-09 13:06:36 (GMT) |
| commit | c03e05c2e72f3ea5e797389e7d1042eef85ad37a (patch) | |
| tree | 3a30ddb1b3b35a9b2ea7d233f242c72e74e71e71 /Include/object.h | |
| parent | 0124b5dd28eff7bb80eb7244e97e402a036db13b (diff) | |
| download | cpython-c03e05c2e72f3ea5e797389e7d1042eef85ad37a.zip cpython-c03e05c2e72f3ea5e797389e7d1042eef85ad37a.tar.gz cpython-c03e05c2e72f3ea5e797389e7d1042eef85ad37a.tar.bz2 | |
gh-98724: Fix Py_CLEAR() macro side effects (#99100)
The Py_CLEAR(), Py_SETREF() and Py_XSETREF() macros now only evaluate
their argument once. If an argument has side effects, these side
effects are no longer duplicated.
Add test_py_clear() and test_py_setref() unit tests to _testcapi.
Diffstat (limited to 'Include/object.h')
| -rw-r--r-- | Include/object.h | 19 |
1 files changed, 12 insertions, 7 deletions
diff --git a/Include/object.h b/Include/object.h index 75624fe..a2ed0bd 100644 --- a/Include/object.h +++ b/Include/object.h @@ -598,16 +598,21 @@ 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 = _PyObject_CAST(op); \ - if (_py_tmp != NULL) { \ - (op) = NULL; \ - Py_DECREF(_py_tmp); \ - } \ +#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); \ + } \ } while (0) + /* Function to use in case the object pointer can be NULL: */ static inline void Py_XINCREF(PyObject *op) { |