merge 3.3 (#24096)

diff --cc Lib/test/test_warnings.py
Simple merge

diff --cc Misc/NEWS
index b787c840625c6ce9c60feb50771e099997ea8e5f,827d761bf9f6838f561f55b165df5d2544fc2e38..b8d2ab14feefe8cc2278b50f45df6ef3b3afd648
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -10,27 -10,9 +10,30 @@@ Release date: tb
  Core and Builtins
  -----------------
  
+ - Issue #24096: Make warnings.warn_explicit more robust against mutation of the
+   warnings.filters list.
+ 
 +- Issue #23996: Avoid a crash when a delegated generator raises an
 +  unnormalized StopIteration exception.  Patch by Stefan Behnel.
 +
 +- Issue #24022: Fix tokenizer crash when processing undecodable source code.
 +
 +- Issue #23309: Avoid a deadlock at shutdown if a daemon thread is aborted
 +  while it is holding a lock to a buffered I/O object, and the main thread
 +  tries to use the same I/O object (typically stdout or stderr).  A fatal
 +  error is emitted instead.
 +
 +- Issue #22977: Fixed formatting Windows error messages on Wine.
 +  Patch by Martin Panter.
 +
 +- Issue #23803: Fixed str.partition() and str.rpartition() when a separator
 +  is wider then partitioned string.
 +
 +- Issue #23192: Fixed generator lambdas.  Patch by Bruno Cauet.
 +
 +- Issue #23629: Fix the default __sizeof__ implementation for variable-sized
 +  objects.
 +
  - Issue #24044: Fix possible null pointer dereference in list.sort in out of
    memory conditions.
  

diff --cc Python/_warnings.c
index bef56479b3357d621f3d36f070bf15dab8686245,d274789f4a677c10a4ded78d897852e668e84473..6dff0a2c114a502a8054a3adb4b2b8c90d90b915
--- 1/Python/_warnings.c
--- 2/Python/_warnings.c
+++ b/Python/_warnings.c
@@@ -101,8 -98,8 +101,8 @@@ get_default_action(void
  }
  
  
- /* The item is a borrowed reference. */
+ /* The item is a new reference. */
 -static const char *
 +static PyObject*
  get_filter(PyObject *category, PyObject *text, Py_ssize_t lineno,
             PyObject *module, PyObject **item)
  {
@@@ -147,28 -145,29 +148,43 @@@
          ln_obj = PyTuple_GET_ITEM(tmp_item, 4);
  
          good_msg = check_matched(msg, text);
-         if (good_msg == -1)
++        if (good_msg == -1) {
++            Py_DECREF(tmp_item);
 +            return NULL;
++        }
 +
          good_mod = check_matched(mod, module);
-         if (good_mod == -1)
++        if (good_mod == -1) {
++            Py_DECREF(tmp_item);
 +            return NULL;
++        }
 +
          is_subclass = PyObject_IsSubclass(category, cat);
-         if (is_subclass == -1)
++        if (is_subclass == -1) {
++            Py_DECREF(tmp_item);
 +            return NULL;
++        }
 +
          ln = PyLong_AsSsize_t(ln_obj);
-         if (ln == -1 && PyErr_Occurred())
 -        if (good_msg == -1 || good_mod == -1 || is_subclass == -1 ||
 -            (ln == -1 && PyErr_Occurred())) {
++        if (ln == -1 && PyErr_Occurred()) {
+             Py_DECREF(tmp_item);
              return NULL;
+         }
  
-         if (good_msg && is_subclass && good_mod && (ln == 0 || lineno == ln))
+         if (good_msg && is_subclass && good_mod && (ln == 0 || lineno == ln)) {
+             *item = tmp_item;
 -            return _PyUnicode_AsString(action);
 +            return action;
+         }
+ 
+         Py_DECREF(tmp_item);
      }
  
      action = get_default_action();
-     if (action != NULL)
+     if (action != NULL) {
+         Py_INCREF(Py_None);
+         *item = Py_None;
 -        return _PyUnicode_AsString(action);
 +        return action;
+     }
  
      PyErr_SetString(PyExc_ValueError,
                      MODULE_NAME ".defaultaction not found");
@@@ -349,17 -304,10 +365,17 @@@ warn_explicit(PyObject *category, PyObj
                PyObject *module, PyObject *registry, PyObject *sourceline)
  {
      PyObject *key = NULL, *text = NULL, *result = NULL, *lineno_obj = NULL;
-     PyObject *item = Py_None;
+     PyObject *item = NULL;
 -    const char *action;
 +    PyObject *action;
      int rc;
  
 +    /* module can be None if a warning is emitted late during Python shutdown.
 +       In this case, the Python warnings module was probably unloaded, filters
 +       are no more available to choose as action. It is safer to ignore the
 +       warning and do nothing. */
 +    if (module == Py_None)
 +        Py_RETURN_NONE;
 +
      if (registry && !PyDict_Check(registry) && (registry != Py_None)) {
          PyErr_SetString(PyExc_TypeError, "'registry' must be a dict");
          return NULL;