gh-112066: Use `PyDict_SetDefaultRef` in place of `PyDict_SetDefault`. (#112211)

This changes a number of internal usages of `PyDict_SetDefault` to use `PyDict_SetDefaultRef`.

Co-authored-by: Erlend E. Aasland <erlend.aasland@protonmail.com>

1 files changed, 17 insertions, 12 deletions

diff --git a/Python/compile.c b/Python/compile.c
index 4c1d3bb..15e5cf3 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -958,14 +958,15 @@ merge_consts_recursive(PyObject *const_cache, PyObject *o)
         return NULL;
     }
 
-    // t is borrowed reference
-    PyObject *t = PyDict_SetDefault(const_cache, key, key);
-    if (t != key) {
-        // o is registered in const_cache.  Just use it.
-        Py_XINCREF(t);
+    PyObject *t;
+    int res = PyDict_SetDefaultRef(const_cache, key, key, &t);
+    if (res != 0) {
+        // o was not inserted into const_cache. t is either the existing value
+        // or NULL (on error).
         Py_DECREF(key);
         return t;
     }
+    Py_DECREF(t);
 
     // We registered o in const_cache.
     // When o is a tuple or frozenset, we want to merge its
@@ -7527,22 +7528,26 @@ _PyCompile_ConstCacheMergeOne(PyObject *const_cache, PyObject **obj)
         return ERROR;
     }
 
-    // t is borrowed reference
-    PyObject *t = PyDict_SetDefault(const_cache, key, key);
+    PyObject *t;
+    int res = PyDict_SetDefaultRef(const_cache, key, key, &t);
     Py_DECREF(key);
-    if (t == NULL) {
+    if (res < 0) {
         return ERROR;
     }
-    if (t == key) {  // obj is new constant.
+    if (res == 0) {  // inserted: obj is new constant.
+        Py_DECREF(t);
         return SUCCESS;
     }
 
     if (PyTuple_CheckExact(t)) {
-        // t is still borrowed reference
-        t = PyTuple_GET_ITEM(t, 1);
+        PyObject *item = PyTuple_GET_ITEM(t, 1);
+        Py_SETREF(*obj, Py_NewRef(item));
+        Py_DECREF(t);
+    }
+    else {
+        Py_SETREF(*obj, t);
     }
 
-    Py_SETREF(*obj, Py_NewRef(t));
     return SUCCESS;
 }