pythongh-91502: Add a new API to check if a frame is an entry frame (pythonGH-91503)

Author: pablogsal

Include/cpython/frameobject.h

@@ -19,6 +19,16 @@ PyAPI_FUNC(PyFrameObject *) PyFrame_New(PyThreadState *, PyCodeObject *,
 
 PyAPI_FUNC(void) PyFrame_LocalsToFast(PyFrameObject *, int);
 
+/* -- Caveat emptor --
+ * The concept of entry frames is an implementation detail of the CPython
+ * interpreter. This API is considered unstable and is provided for the
+ * convenience of debuggers, profilers and state-inspecting tools. Notice that
+ * this API can be changed in future minor versions if the underlying frame
+ * mechanism change or the concept of an 'entry frame' or its semantics becomes
+ * obsolete or outdated. */
+
+PyAPI_FUNC(int) _PyFrame_IsEntryFrame(PyFrameObject *frame);
+
 PyAPI_FUNC(int) PyFrame_FastToLocalsWithError(PyFrameObject *f);
 PyAPI_FUNC(void) PyFrame_FastToLocals(PyFrameObject *);
 

Misc/NEWS.d/next/Core and Builtins/2022-04-13-11-15-09.gh-issue-91502.11YXHQ.rst

@@ -0,0 +1,2 @@
+Add a new :c:func:`_PyFrame_IsEntryFrame` API function, to check if a
+:c:type:`PyFrameObject` is an entry frame. Patch by Pablo Galindo.

Objects/frameobject.c

@@ -1104,6 +1104,14 @@ PyFrame_LocalsToFast(PyFrameObject *f, int clear)
     }
 }
 
+
+int _PyFrame_IsEntryFrame(PyFrameObject *frame)
+{
+    assert(frame != NULL);
+    return frame->f_frame->is_entry;
+}
+
+
 PyCodeObject *
 PyFrame_GetCode(PyFrameObject *frame)
 {