GH-128682: Change a couple of functions to only steal references on success. (GH-129132)

Change PyTuple_FromStackRefSteal and PyList_FromStackRefSteal to only steal on success to avoid escaping

Author: markshannon

Include/internal/pycore_list.h

@@ -61,7 +61,7 @@ typedef struct {
 
 union _PyStackRef;
 
-PyAPI_FUNC(PyObject *)_PyList_FromStackRefSteal(const union _PyStackRef *src, Py_ssize_t n);
+PyAPI_FUNC(PyObject *)_PyList_FromStackRefStealOnSuccess(const union _PyStackRef *src, Py_ssize_t n);
 PyAPI_FUNC(PyObject *)_PyList_AsTupleAndClear(PyListObject *v);
 
 #ifdef __cplusplus

Include/internal/pycore_opcode_metadata.h

@@ -21,7 +21,7 @@ extern PyStatus _PyTuple_InitGlobalObjects(PyInterpreterState *);
 #define _PyTuple_ITEMS(op) _Py_RVALUE(_PyTuple_CAST(op)->ob_item)
 
 PyAPI_FUNC(PyObject *)_PyTuple_FromArray(PyObject *const *, Py_ssize_t);
-PyAPI_FUNC(PyObject *)_PyTuple_FromStackRefSteal(const union _PyStackRef *, Py_ssize_t);
+PyAPI_FUNC(PyObject *)_PyTuple_FromStackRefStealOnSuccess(const union _PyStackRef *, Py_ssize_t);
 PyAPI_FUNC(PyObject *)_PyTuple_FromArraySteal(PyObject *const *, Py_ssize_t);
 
 typedef struct {

Include/internal/pycore_tuple.h

@@ -3190,17 +3190,14 @@ _PyList_AsTupleAndClear(PyListObject *self)
 }
 
 PyObject *
-_PyList_FromStackRefSteal(const _PyStackRef *src, Py_ssize_t n)
+_PyList_FromStackRefStealOnSuccess(const _PyStackRef *src, Py_ssize_t n)
 {
     if (n == 0) {
         return PyList_New(0);
     }
 
     PyListObject *list = (PyListObject *)PyList_New(n);
     if (list == NULL) {
-        for (Py_ssize_t i = 0; i < n; i++) {
-            PyStackRef_CLOSE(src[i]);
-        }
         return NULL;
     }
 

Include/internal/pycore_uop_metadata.h

@@ -391,16 +391,13 @@ _PyTuple_FromArray(PyObject *const *src, Py_ssize_t n)
 }
 
 PyObject *
-_PyTuple_FromStackRefSteal(const _PyStackRef *src, Py_ssize_t n)
+_PyTuple_FromStackRefStealOnSuccess(const _PyStackRef *src, Py_ssize_t n)
 {
     if (n == 0) {
         return tuple_get_empty();
     }
     PyTupleObject *tuple = tuple_alloc(n);
     if (tuple == NULL) {
-        for (Py_ssize_t i = 0; i < n; i++) {
-            PyStackRef_CLOSE(src[i]);
-        }
         return NULL;
     }
     PyObject **dst = tuple->ob_item;

Objects/listobject.c

@@ -1852,16 +1852,20 @@ dummy_func(
         }
 
         inst(BUILD_TUPLE, (values[oparg] -- tup)) {
-            PyObject *tup_o = _PyTuple_FromStackRefSteal(values, oparg);
+            PyObject *tup_o = _PyTuple_FromStackRefStealOnSuccess(values, oparg);
+            if (tup_o == NULL) {
+                ERROR_NO_POP();
+            }
             INPUTS_DEAD();
-            ERROR_IF(tup_o == NULL, error);
             tup = PyStackRef_FromPyObjectSteal(tup_o);
         }
 
         inst(BUILD_LIST, (values[oparg] -- list)) {
-            PyObject *list_o = _PyList_FromStackRefSteal(values, oparg);
+            PyObject *list_o = _PyList_FromStackRefStealOnSuccess(values, oparg);
+            if (list_o == NULL) {
+                ERROR_NO_POP();
+            }
             INPUTS_DEAD();
-            ERROR_IF(list_o == NULL, error);
             list = PyStackRef_FromPyObjectSteal(list_o);
         }
 

Objects/tupleobject.c

@@ -1527,7 +1527,12 @@ initialize_locals(PyThreadState *tstate, PyFunctionObject *func,
             u = (PyObject *)&_Py_SINGLETON(tuple_empty);
         }
         else {
-            u = _PyTuple_FromStackRefSteal(args + n, argcount - n);
+            u = _PyTuple_FromStackRefStealOnSuccess(args + n, argcount - n);
+            if (u == NULL) {
+                for (Py_ssize_t i = n; i < argcount; i++) {
+                    PyStackRef_CLOSE(args[i]);
+                }
+            }
         }
         if (u == NULL) {
             goto fail_post_positional;

Python/bytecodes.c

@@ -581,7 +581,7 @@ def has_error_without_pop(op: parser.InstDef) -> bool:
     "_PyGen_GetGeneratorFromFrame",
     "_PyInterpreterState_GET",
     "_PyList_AppendTakeRef",
-    "_PyList_FromStackRefSteal",
+    "_PyList_FromStackRefStealOnSuccess",
     "_PyList_ITEMS",
     "_PyLong_Add",
     "_PyLong_CompactValue",
@@ -600,8 +600,7 @@ def has_error_without_pop(op: parser.InstDef) -> bool:
     "_PyObject_InlineValues",
     "_PyObject_ManagedDictPointer",
     "_PyThreadState_HasStackSpace",
-    "_PyTuple_FromArraySteal",
-    "_PyTuple_FromStackRefSteal",
+    "_PyTuple_FromStackRefStealOnSuccess",
     "_PyTuple_ITEMS",
     "_PyType_HasFeature",
     "_PyType_NewManagedObject",