PEP 809: Updates from discussion

peps/pep-0809.rst

@@ -157,6 +157,18 @@ are not permitted. That is, the APIs to detect whether a particular behaviour is
 expected on the current Python release must have been available on all earlier
 releases that support the ABI.
 
+Accidental changes that occur in releases should be reverted as soon as
+discovered, ideally without breaking regular compatibility rules. However, it is
+better to have ``3.x.1`` fix a Stable ABI issue introduced in ``3.x.0`` rather
+than to leave it present until ``3.y.0``.
+
+Historically, we have used clever C preprocessor constructs to try and preserve
+both source and binary-level compatibility, for example, by selecting macro or
+inline functions automatically. Under this new scheme, these should be avoided
+in favour of a much more direct relationship between the documented C API and
+the shape of the ABI. Changes can be scheduled for the next version of the ABI
+if they are important enough to be made.
+
 
 Opaque PyObject
 ---------------
@@ -252,13 +264,25 @@ same operation, but less efficiently. The final result of this example is a
 single extension module that is binary compatible with *all* releases supporting
 ``abi2026`` but is more efficient when running against newer releases of Python.
 
+Additionally, ``PyInterface_Get(void *intf)`` will return a global struct, for
+APIs that are not specific to a particular object. It is intended that the two
+"get" APIs will support different interfaces, even though they share the
+namespace. APIs provided through the struct for a global interface will almost
+always require a runtime or interpreter parameter, which is unnecessary when an
+object is available. Further, ``PyInterface_Get`` will not require a Python
+thread to be attached (a.k.a. the GIL is not required), though any functions
+provided by an interface may require it.
+
 Overview complete, here is the full specification of each new API:
 
 .. code-block:: c
 
    // Abstract API to request an interface for an object (or type).
    PyAPI_FUNC(int) PyObject_GetInterface(PyObject *obj, void *intf);
 
+   // API to request a global interface
+   PyAPI_FUNC(int) PyInterface_Get(void *intf);
+
    // API to release an interface.
    PyAPI_FUNC(int) PyInterface_Release(void *intf);