From 91b69b77cf5f78de6d35dea23098df34b6fd9e53 Mon Sep 17 00:00:00 2001
From: Petr Viktorin <encukou@gmail.com>
Date: Fri, 23 Apr 2021 14:23:38 +0200
Subject: [PATCH] bpo-43868: Remove PyOS_ReadlineFunctionPointer from the
 stable ABI list (GH-25442)

The inclusion of PyOS_ReadlineFunctionPointer in python3dll.c was a mistake.

According to PEP 384:
> functions expecting FILE* are not part of the ABI, to avoid depending
> on a specific version of the Microsoft C runtime DLL on Windows.

https://bugs.python.org/issue43868
---
 Doc/whatsnew/3.10.rst                                       | 6 ++++++
 Include/cpython/pythonrun.h                                 | 1 +
 Include/pythonrun.h                                         | 1 -
 .../next/C API/2021-04-16-18-15-56.bpo-43868.twQ7KH.rst     | 3 +++
 PC/python3dll.c                                             | 1 -
 5 files changed, 10 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/C API/2021-04-16-18-15-56.bpo-43868.twQ7KH.rst

diff --git a/Doc/whatsnew/3.10.rst b/Doc/whatsnew/3.10.rst
index 1c2919a06c4..67e03f2f5ef 100644
--- a/Doc/whatsnew/3.10.rst
+++ b/Doc/whatsnew/3.10.rst
@@ -1740,6 +1740,12 @@ Removed
   Use Python :mod:`symtable` module instead.
   (Contributed by Victor Stinner in :issue:`43244`.)
 
+* Remove :c:func:`PyOS_ReadlineFunctionPointer` from the limited C API headers
+  and from ``python3.dll``, the library that provides the stable ABI on
+  Windows. Since the function takes a ``FILE*`` argument, its ABI stability
+  cannot be guaranteed.
+  (Contributed by Petr Viktorin in :issue:`43868`.)
+
 * Remove ``ast.h``, ``asdl.h``, and ``Python-ast.h`` header files.
   These functions were undocumented and excluded from the limited C API.
   Most names defined by these header files were not prefixed by ``Py`` and so
diff --git a/Include/cpython/pythonrun.h b/Include/cpython/pythonrun.h
index ffca0e457d5..2e72d0820d3 100644
--- a/Include/cpython/pythonrun.h
+++ b/Include/cpython/pythonrun.h
@@ -118,3 +118,4 @@ PyAPI_FUNC(PyObject *) PyRun_FileFlags(FILE *fp, const char *p, int s, PyObject
 /* Stuff with no proper home (yet) */
 PyAPI_FUNC(char *) PyOS_Readline(FILE *, FILE *, const char *);
 PyAPI_DATA(PyThreadState*) _PyOS_ReadlineTState;
+PyAPI_DATA(char) *(*PyOS_ReadlineFunctionPointer)(FILE *, FILE *, const char *);
diff --git a/Include/pythonrun.h b/Include/pythonrun.h
index b87bc738902..b0a2fc3002d 100644
--- a/Include/pythonrun.h
+++ b/Include/pythonrun.h
@@ -16,7 +16,6 @@ PyAPI_FUNC(void) PyErr_Display(PyObject *, PyObject *, PyObject *);
 
 /* Stuff with no proper home (yet) */
 PyAPI_DATA(int) (*PyOS_InputHook)(void);
-PyAPI_DATA(char) *(*PyOS_ReadlineFunctionPointer)(FILE *, FILE *, const char *);
 
 /* Stack size, in "pointers" (so we get extra safety margins
    on 64-bit platforms).  On a 32-bit platform, this translates
diff --git a/Misc/NEWS.d/next/C API/2021-04-16-18-15-56.bpo-43868.twQ7KH.rst b/Misc/NEWS.d/next/C API/2021-04-16-18-15-56.bpo-43868.twQ7KH.rst
new file mode 100644
index 00000000000..50888b8b37a
--- /dev/null
+++ b/Misc/NEWS.d/next/C API/2021-04-16-18-15-56.bpo-43868.twQ7KH.rst	
@@ -0,0 +1,3 @@
+:c:func:`PyOS_ReadlineFunctionPointer` is no longer exported by limited C API
+headers and by ``python3.dll`` on Windows. Like any function that takes
+``FILE*``, it is not part of the stable ABI.
diff --git a/PC/python3dll.c b/PC/python3dll.c
index 195c6531fdf..e5a21ed7c02 100644
--- a/PC/python3dll.c
+++ b/PC/python3dll.c
@@ -808,7 +808,6 @@ EXPORT_DATA(PyODictIter_Type)
 EXPORT_DATA(PyODictKeys_Type)
 EXPORT_DATA(PyODictValues_Type)
 EXPORT_DATA(PyOS_InputHook)
-EXPORT_DATA(PyOS_ReadlineFunctionPointer)
 EXPORT_DATA(PyProperty_Type)
 EXPORT_DATA(PyRange_Type)
 EXPORT_DATA(PyRangeIter_Type)