bpo-44964: Add a note explaining the new semantics of f_last_i in frame objects (GH-28200)
(cherry picked from commit fa2c0b85a8d5c9486661083afdf38cbaadb3432a)
Co-authored-by: Pablo Galindo Salgado <Pablogsal@gmail.com>
diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst
index eefdc3d..477daae 100644
--- a/Doc/reference/datamodel.rst
+++ b/Doc/reference/datamodel.rst
@@ -1034,8 +1034,9 @@
:attr:`f_code` is the code object being executed in this frame; :attr:`f_locals`
is the dictionary used to look up local variables; :attr:`f_globals` is used for
global variables; :attr:`f_builtins` is used for built-in (intrinsic) names;
- :attr:`f_lasti` gives the precise instruction (this is an index into the
- bytecode string of the code object).
+ :attr:`f_lasti` gives the precise instruction (it represents a wordcode index, which
+ means that to get an index into the bytecode string of the code object it needs to be
+ multiplied by 2).
Accessing ``f_code`` raises an :ref:`auditing event <auditing>`
``object.__getattr__`` with arguments ``obj`` and ``"f_code"``.
diff --git a/Doc/whatsnew/3.10.rst b/Doc/whatsnew/3.10.rst
index 068eb76..dbf8923 100644
--- a/Doc/whatsnew/3.10.rst
+++ b/Doc/whatsnew/3.10.rst
@@ -1944,6 +1944,12 @@
source_buf = PyBytes_AsString(source_bytes_object);
code = Py_CompileString(source_buf, filename, Py_file_input);
+ * For ``FrameObject`` objects, the ``f_lasti`` member now represents a wordcode
+ offset instead of a simple offset into the bytecode string. This means that this
+ number needs to be multiplied by 2 to be used with APIs that expect a byte offset
+ instead (like :c:func:`PyCode_Addr2Line` for example). Notice as well that the
+ ``f_lasti`` member of ``FrameObject`` objects is not considered stable.
+
CPython bytecode changes
========================