Make it explicit that shim frame is artificial and should not show up in tracebacks or sys._getframe()

Author: markshannon

Include/internal/pycore_frame.h

@@ -61,6 +61,7 @@ typedef struct _PyInterpreterFrame {
     _Py_CODEUNIT *prev_instr;
     int stacktop;     /* Offset of TOS from localsplus  */
     bool is_entry;  // Whether this is the "root" frame for the current _PyCFrame.
+    bool is_artificial; // Hide this frame in backtraces.
     char owner;
     /* Locals and stack */
     PyObject *localsplus[1];
@@ -109,6 +110,7 @@ _PyFrame_InitializeSpecials(
     frame->frame_obj = NULL;
     frame->prev_instr = _PyCode_CODE(frame->f_code) - 1;
     frame->is_entry = false;
+    frame->is_artificial = false;
     frame->owner = FRAME_OWNED_BY_THREAD;
 }
 

Python/ceval.c

@@ -1574,7 +1574,7 @@ eval_frame_handle_pending(PyThreadState *tstate)
     Py_INCREF(res);
 
 #define TRACE_FUNCTION_EXIT() \
-    if (cframe.use_tracing) { \
+    if (cframe.use_tracing && !frame->is_artificial) { \
         if (trace_function_exit(tstate, frame, retval)) { \
             Py_DECREF(retval); \
             goto exit_unwind; \
@@ -5010,6 +5010,7 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, _PyInterpreterFrame *frame, int
             if (shim == NULL) {
                 goto error;
             }
+            shim->is_artificial = true;
             CALL_STAT_INC(inlined_py_calls);
             shim->previous = frame;
             shim->prev_instr = _PyCode_CODE(shim->f_code) + 1;

Python/frame.c

@@ -70,7 +70,11 @@ take_ownership(PyFrameObject *f, _PyInterpreterFrame *frame)
     assert(f->f_back == NULL);
     if (frame->previous != NULL) {
         /* Link PyFrameObjects.f_back and remove link through _PyInterpreterFrame.previous */
-        PyFrameObject *back = _PyFrame_GetFrameObject(frame->previous);
+        _PyInterpreterFrame *prev = frame->previous;
+        while (prev->is_artificial) {
+            prev = prev->previous;
+        }
+        PyFrameObject *back = _PyFrame_GetFrameObject(prev);
         if (back == NULL) {
             /* Memory error here. */
             assert(PyErr_ExceptionMatches(PyExc_MemoryError));

Python/sysmodule.c

@@ -1778,7 +1778,9 @@ sys__getframe_impl(PyObject *module, int depth)
 
     while (depth > 0 && frame != NULL) {
         frame = frame->previous;
-        --depth;
+        if (!frame->is_artificial) {
+            --depth;
+        }
     }
     if (frame == NULL) {
         _PyErr_SetString(tstate, PyExc_ValueError,