bpo-44590: Lazily allocate frame objects (GH-27077)

* Convert "specials" array to InterpreterFrame struct, adding f_lasti, f_state and other non-debug FrameObject fields to it.

* Refactor, calls pushing the call to the interpreter upward toward _PyEval_Vector.

* Compute f_back when on thread stack, only filling in value when frame object outlives stack invocation.

* Move ownership of InterpreterFrame in generator from frame object to generator object.

* Do not create frame objects for Python calls.

* Do not create frame objects for generators.

1 files changed, 7 insertions, 9 deletions

diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index f809e2fda56..5dfa917e8ff 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -29,6 +29,7 @@ Data members:
 
 #include "code.h"
 #include "frameobject.h"          // PyFrame_GetBack()
+#include "pycore_frame.h"
 #include "pydtrace.h"
 #include "osdefs.h"               // DELIM
 #include "stdlib_module_names.h"  // _Py_stdlib_module_names
@@ -1814,25 +1815,22 @@ sys__getframe_impl(PyObject *module, int depth)
 /*[clinic end generated code: output=d438776c04d59804 input=c1be8a6464b11ee5]*/
 {
     PyThreadState *tstate = _PyThreadState_GET();
-    PyFrameObject *f = PyThreadState_GetFrame(tstate);
+    InterpreterFrame *frame = tstate->frame;
 
-    if (_PySys_Audit(tstate, "sys._getframe", "O", f) < 0) {
-        Py_DECREF(f);
+    if (_PySys_Audit(tstate, "sys._getframe", NULL) < 0) {
         return NULL;
     }
 
-    while (depth > 0 && f != NULL) {
-        PyFrameObject *back = PyFrame_GetBack(f);
-        Py_DECREF(f);
-        f = back;
+    while (depth > 0 && frame != NULL) {
+        frame = frame->previous;
         --depth;
     }
-    if (f == NULL) {
+    if (frame == NULL) {
         _PyErr_SetString(tstate, PyExc_ValueError,
                          "call stack is not deep enough");
         return NULL;
     }
-    return (PyObject*)f;
+    return _Py_XNewRef((PyObject *)_PyFrame_GetFrameObject(frame));
 }
 
 /*[clinic input]