Fix memory leak in SET_ITEM macro in initconfig.c when expression evaluation fails

Author: Wulian233

Misc/NEWS.d/next/Core_and_Builtins/2026-03-21-16-24-10.gh-issue-146244.Oztf9i.rst

@@ -0,0 +1,2 @@
+Fix memory leak in ``SET_ITEM`` macro in ``initconfig.c`` when expression
+evaluation fails

Python/initconfig.c

@@ -508,17 +508,16 @@ _Py_COMP_DIAG_IGNORE_DEPR_DECLS
     }
 
 #define SET_ITEM(KEY, EXPR) \
-        do { \
-            obj = (EXPR); \
-            if (obj == NULL) { \
-                return NULL; \
-            } \
-            int res = PyDict_SetItemString(dict, (KEY), obj); \
+    do { \
+        obj = (EXPR); \
+        if (obj == NULL) \
+            goto fail; \
+        if (PyDict_SetItemString(dict, (KEY), obj) < 0) { \
             Py_DECREF(obj); \
-            if (res < 0) { \
-                goto fail; \
-            } \
-        } while (0)
+            goto fail; \
+        } \
+        Py_DECREF(obj); \
+    } while (0)
 #define SET_ITEM_INT(VAR) \
     SET_ITEM(#VAR, PyLong_FromLong(VAR))
 #define FROM_STRING(STR) \