Various small clarifications as suggested by Pablo.

python · markshannon · Jul 26, 2021 · Jun 21, 2021 · Jun 22, 2021 · Jun 22, 2021
commit 90ed5b6b0fb1c46349e2701075433782417cbe75
diff --git a/Include/internal/pycore_frame.h b/Include/internal/pycore_frame.h
@@ -49,7 +49,7 @@ static inline int _PyFrameHasCompleted(InterpreterFrame *f) {
 
 #define FRAME_SPECIALS_SIZE ((sizeof(InterpreterFrame)-1)/sizeof(PyObject *))
 
-void _PyFrame_TakeLocals(PyFrameObject *f, InterpreterFrame *locals);
+void _PyFrame_TakeInterpreterFrame(PyFrameObject *f, InterpreterFrame *locals);
 
 static inline void
 _PyFrame_InitializeSpecials(
@@ -107,13 +107,13 @@ _PyFrame_GetFrameObject(InterpreterFrame *frame)
 }
 
 /* Clears all references in the frame.
- * If take is non-zero, then the frame
- * may be transfered to the frame object
+ * If take is non-zero, then the InterpreterFrame frame
+ * may be transfered to the frame object it references
  * instead of being cleared. Either way
  * the caller no longer owns the references
  * in the frame.
  * take should  be set to 1 for heap allocated
- * frames.
+ * frames like the ones in generators and coroutines.
  */
 int
 _PyFrame_Clear(InterpreterFrame * frame, int take);
@@ -124,6 +124,11 @@ _PyFrame_FastToLocalsWithError(InterpreterFrame *frame);
 void
 _PyFrame_LocalsToFast(InterpreterFrame *frame, int clear);
 
+InterpreterFrame *_PyThreadState_PushFrame(
+    PyThreadState *tstate, PyFrameConstructor *con, PyObject *locals);
+
+void _PyThreadState_PopFrame(PyThreadState *tstate, InterpreterFrame *frame);
+
 #ifdef __cplusplus
 }
 #endif

@@ -147,11 +147,6 @@ PyAPI_FUNC(int) _PyState_AddModule(
 
 PyAPI_FUNC(int) _PyOS_InterruptOccurred(PyThreadState *tstate);
 
-struct _interpreter_frame *_PyThreadState_PushFrame(
-    PyThreadState *tstate, PyFrameConstructor *con, PyObject *locals);
-
-void _PyThreadState_PopFrame(PyThreadState *tstate, struct _interpreter_frame *frame);
-
 #ifdef __cplusplus
 }
 #endif

@@ -857,7 +857,7 @@ frame_alloc(InterpreterFrame *frame, int owns)
 }
 
 void
-_PyFrame_TakeLocals(PyFrameObject *f, InterpreterFrame *frame)
+_PyFrame_TakeInterpreterFrame(PyFrameObject *f, InterpreterFrame *frame)
 {
     assert(f->f_own_locals_memory == 0);
     assert(frame->frame_obj == NULL);
@@ -866,17 +866,20 @@ _PyFrame_TakeLocals(PyFrameObject *f, InterpreterFrame *frame)
     f->f_frame = frame;
     assert(f->f_back == NULL);
     if (frame->previous != NULL) {
+        /* Link PyFrameObjects.f_back and remove link through InterpreterFrame.previous */
         PyFrameObject *back = _PyFrame_GetFrameObject(frame->previous);
         if (back == NULL) {
-            /* Memory error here. Nothing we can do about it */
+            /* Memory error here. */
+            assert(_PyErr_GetTopmostException(_PyThreadState_GET())->exc_type == PyExc_MemoryError);
+            /* Nothing we can do about it */
             PyErr_Clear();
             _PyErr_WriteUnraisableMsg("Out of memory lazily allocating frame->f_back", NULL);
         }
         else {
             f->f_back = (PyFrameObject *)Py_NewRef(back);
         }
+        frame->previous = NULL;
     }
-    frame->previous = NULL;
     if (!_PyObject_GC_IS_TRACKED((PyObject *)f)) {
         _PyObject_GC_TRACK((PyObject *)f);
     }

@@ -8887,6 +8887,7 @@ super_init_without_args(PyFrameObject *f, PyCodeObject *co,
         return -1;
     }
 
+    assert(f->f_frame->nlocalsplus > 0);
     PyObject *firstarg = _PyFrame_GetLocalsArray(f->f_frame)[0];
     // The first argument might be a cell.
     if (firstarg != NULL && (_PyLocals_GetKind(co->co_localspluskinds, 0) & CO_FAST_CELL)) {

@@ -5162,7 +5162,7 @@ _PyFrame_Clear(InterpreterFrame * frame, int take)
                     return -1;
                 }
             }
-            _PyFrame_TakeLocals(f, frame);
+            _PyFrame_TakeInterpreterFrame(f, frame);
             Py_DECREF(f);
             return 0;
         }

@@ -2042,7 +2042,7 @@ _PyThreadState_PushFrame(PyThreadState *tstate, PyFrameConstructor *con, PyObjec
 {
     PyCodeObject *code = (PyCodeObject *)con->fc_code;
     int nlocalsplus = code->co_nlocalsplus;
-    int size = nlocalsplus + code->co_stacksize +
+    size_t size = nlocalsplus + code->co_stacksize +
         FRAME_SPECIALS_SIZE;
     PyObject **localsarray = tstate->datastack_top;
     PyObject **top = localsarray + size;