gh-108308: config_dict_get() uses PyDict_GetItemRef() (#108371)

Replace _PyDict_GetItemStringWithError() with PyDict_GetItemRef() in
config_dict_get() to get a strong reference to the item.

Author: vstinner

Python/initconfig.c

@@ -1,5 +1,4 @@
 #include "Python.h"
-#include "pycore_dict.h"          // _PyDict_GetItemStringWithError()
 #include "pycore_fileutils.h"     // _Py_HasFileSystemDefaultEncodeErrors
 #include "pycore_getopt.h"        // _PyOS_GetOpt()
 #include "pycore_initconfig.h"    // _PyStatus_OK()
@@ -1065,8 +1064,11 @@ _PyConfig_AsDict(const PyConfig *config)
 static PyObject*
 config_dict_get(PyObject *dict, const char *name)
 {
-    PyObject *item = _PyDict_GetItemStringWithError(dict, name);
-    if (item == NULL && !PyErr_Occurred()) {
+    PyObject *item;
+    if (PyDict_GetItemStringRef(dict, name, &item) < 0) {
+        return NULL;
+    }
+    if (item == NULL) {
         PyErr_Format(PyExc_ValueError, "missing config key: %s", name);
         return NULL;
     }
@@ -1096,6 +1098,7 @@ config_dict_get_int(PyObject *dict, const char *name, int *result)
         return -1;
     }
     int value = _PyLong_AsInt(item);
+    Py_DECREF(item);
     if (value == -1 && PyErr_Occurred()) {
         if (PyErr_ExceptionMatches(PyExc_TypeError)) {
             config_dict_invalid_type(name);
@@ -1118,6 +1121,7 @@ config_dict_get_ulong(PyObject *dict, const char *name, unsigned long *result)
         return -1;
     }
     unsigned long value = PyLong_AsUnsignedLong(item);
+    Py_DECREF(item);
     if (value == (unsigned long)-1 && PyErr_Occurred()) {
         if (PyErr_ExceptionMatches(PyExc_TypeError)) {
             config_dict_invalid_type(name);
@@ -1140,27 +1144,33 @@ config_dict_get_wstr(PyObject *dict, const char *name, PyConfig *config,
     if (item == NULL) {
         return -1;
     }
+
     PyStatus status;
     if (item == Py_None) {
         status = PyConfig_SetString(config, result, NULL);
     }
     else if (!PyUnicode_Check(item)) {
         config_dict_invalid_type(name);
-        return -1;
+        goto error;
     }
     else {
         wchar_t *wstr = PyUnicode_AsWideCharString(item, NULL);
         if (wstr == NULL) {
-            return -1;
+            goto error;
         }
         status = PyConfig_SetString(config, result, wstr);
         PyMem_Free(wstr);
     }
     if (_PyStatus_EXCEPTION(status)) {
         PyErr_NoMemory();
-        return -1;
+        goto error;
     }
+    Py_DECREF(item);
     return 0;
+
+error:
+    Py_DECREF(item);
+    return -1;
 }
 
 
@@ -1174,6 +1184,7 @@ config_dict_get_wstrlist(PyObject *dict, const char *name, PyConfig *config,
     }
 
     if (!PyList_CheckExact(list)) {
+        Py_DECREF(list);
         config_dict_invalid_type(name);
         return -1;
     }
@@ -1207,10 +1218,12 @@ config_dict_get_wstrlist(PyObject *dict, const char *name, PyConfig *config,
         goto error;
     }
     _PyWideStringList_Clear(&wstrlist);
+    Py_DECREF(list);
     return 0;
 
 error:
     _PyWideStringList_Clear(&wstrlist);
+    Py_DECREF(list);
     return -1;
 }