bpo-40421: Add PyFrame_GetCode() function (GH-19757)

PyFrame_GetCode(frame): return a borrowed reference to the frame
code.

Replace frame->f_code with PyFrame_GetCode(frame) in most code,
except in frameobject.c, genobject.c and ceval.c.

Also add PyFrame_GetLineNumber() to the limited C API.

3 files changed, 17 insertions, 2 deletions

diff --git a/Doc/c-api/init.rst b/Doc/c-api/init.rst
index 435808f..afde3db 100644
--- a/Doc/c-api/init.rst
+++ b/Doc/c-api/init.rst
@@ -1074,8 +1074,10 @@ All of the following functions must be called after :c:func:`Py_Initialize`.
 
 .. c:function:: PyFrameObject* PyThreadState_GetFrame(PyThreadState *tstate)
 
-   Get the current frame of the Python thread state *tstate*. It can be
-   ``NULL`` if no frame is currently executing.
+   Get a borrowed reference to the current frame of the Python thread state
+   *tstate*.
+
+   Return ``NULL`` if no frame is currently executing.
 
    See also :c:func:`PyEval_GetFrame`.
 
diff --git a/Doc/c-api/reflection.rst b/Doc/c-api/reflection.rst
index 498219f..b313ea3 100644
--- a/Doc/c-api/reflection.rst
+++ b/Doc/c-api/reflection.rst
@@ -31,6 +31,15 @@ Reflection
    See also :c:func:`PyThreadState_GetFrame`.
 
 
+.. c:function:: int PyFrame_GetCode(PyFrameObject *frame)
+
+   Return a borrowed reference to the *frame* code.
+
+   *frame* must not be ``NULL``.
+
+   .. versionadded:: 3.9
+
+
 .. c:function:: int PyFrame_GetLineNumber(PyFrameObject *frame)
 
    Return the line number that *frame* is currently executing.
diff --git a/Doc/whatsnew/3.9.rst b/Doc/whatsnew/3.9.rst
index 8b8aa9a..e3751fa 100644
--- a/Doc/whatsnew/3.9.rst
+++ b/Doc/whatsnew/3.9.rst
@@ -537,6 +537,10 @@ Optimizations
 Build and C API Changes
 =======================
 
+* New :c:func:`PyFrame_GetCode` function: return a borrowed reference to the
+  frame code.
+  (Contributed by Victor Stinner in :issue:`40421`.)
+
 * Add :c:func:`PyFrame_GetLineNumber` to the limited C API.
   (Contributed by Victor Stinner in :issue:`40421`.)