Emit a deprecation warning about a future change of sys.abiflags availability on Windows

Author: XuehaiPan

Doc/library/sys.rst

@@ -22,6 +22,27 @@ always available. Unless explicitly noted otherwise, all variables are read-only
       Default flags became an empty string (``m`` flag for pymalloc has been
       removed).
 
+   .. versionchanged:: 3.14
+      A deprecation warning will be emitted if the :data:`sys.abiflags` member
+      is accessed on Windows.
+      For example:
+
+      .. code-block:: python
+
+         >>> import sys
+         >>> getattr(sys, 'abiflags', '')
+         DeprecationWarning: sys.abiflags will be set to a meaningful value on all platforms ...
+
+      Due to historical reasons, :data:`sys.abiflags` is not covered by
+      :pep:`3149` on Windows. Now we have multiple builds, such as the
+      :term:`free-threaded <free threading>` build, that provide different ABIs.
+      :data:`sys.abiflags` is now required under many circumstances to determine
+      the ABI of the Python interpreter.
+
+      The :data:`sys.abiflags` member will be set to a meaningful value on
+      Windows in Python 3.16. This means the :data:`sys.abiflags` member will
+      always be available on all platforms starting from Python 3.16.
+
    .. availability:: Unix.
 
 

Lib/test/test_sys.py

@@ -698,6 +698,13 @@ def test_attributes(self):
         self.assertIn(sys.float_repr_style, ('short', 'legacy'))
         if not sys.platform.startswith('win'):
             self.assertIsInstance(sys.abiflags, str)
+        else:
+            absent = object()
+            with self.assertWarnsRegex(
+                DeprecationWarning,
+                r'sys\.abiflags is going to be set.*on all platforms',
+            ):
+                self.assertIs(getattr(sys, 'abiflags', absent), absent)
 
     def test_thread_info(self):
         info = sys.thread_info

Misc/ACKS

@@ -1402,6 +1402,7 @@ Todd R. Palmer
 Juan David Ibáñez Palomar
 Nicola Palumbo
 Jan Palus
+Xuehai Pan
 Yongzhi Pan
 Martin Panter
 Mathias Panzenböck

Python/sysmodule.c

@@ -92,6 +92,16 @@ _PySys_GetRequiredAttr(PyObject *name)
     }
     PyObject *value;
     if (PyDict_GetItemRef(sysdict, name, &value) == 0) {
+#ifndef ABIFLAGS
+            if (_PyUnicode_EqualToASCIIString(name, "abiflags")) {
+                if (PyErr_WarnEx(PyExc_DeprecationWarning,
+                    "sys.abiflags will be set to a meaningful value "
+                    "on all platforms in Python 3.16 instead of absent",
+                    /*stack_level=*/1) < 0) {
+                    return NULL;
+                }
+            }
+#endif
         PyErr_Format(PyExc_RuntimeError, "lost sys.%U", name);
     }
     return value;
@@ -108,6 +118,16 @@ _PySys_GetRequiredAttrString(const char *name)
     }
     PyObject *value;
     if (PyDict_GetItemStringRef(sysdict, name, &value) == 0) {
+#ifndef ABIFLAGS
+            if (strcmp(name, "abiflags") == 0) {
+                if (PyErr_WarnEx(PyExc_DeprecationWarning,
+                    "sys.abiflags will be set to a meaningful value "
+                    "on all platforms in Python 3.16 instead of absent",
+                    /*stack_level=*/1) < 0) {
+                    return NULL;
+                }
+            }
+#endif
         PyErr_Format(PyExc_RuntimeError, "lost sys.%s", name);
     }
     return value;
@@ -129,7 +149,18 @@ _PySys_GetOptionalAttr(PyObject *name, PyObject **value)
         *value = NULL;
         return 0;
     }
-    return PyDict_GetItemRef(sysdict, name, value);
+    int ret = PyDict_GetItemRef(sysdict, name, value);
+#ifndef ABIFLAGS
+    if (ret == 0 && _PyUnicode_EqualToASCIIString(name, "abiflags")) {
+        if (PyErr_WarnEx(PyExc_DeprecationWarning,
+            "sys.abiflags will be set to a meaningful value "
+            "on all platforms in Python 3.16 instead of absent",
+            /*stack_level=*/1) < 0) {
+            return -1;
+        }
+    }
+#endif
+    return ret;
 }
 
 int
@@ -141,7 +172,18 @@ _PySys_GetOptionalAttrString(const char *name, PyObject **value)
         *value = NULL;
         return 0;
     }
-    return PyDict_GetItemStringRef(sysdict, name, value);
+    int ret = PyDict_GetItemStringRef(sysdict, name, value);
+#ifndef ABIFLAGS
+    if (ret == 0 && strcmp(name, "abiflags") == 0) {
+        if (PyErr_WarnEx(PyExc_DeprecationWarning,
+            "sys.abiflags will be set to a meaningful value "
+            "on all platforms in Python 3.16 instead of absent",
+            /*stack_level=*/1) < 0) {
+            return -1;
+        }
+    }
+#endif
+    return ret;
 }
 
 PyObject *
@@ -154,14 +196,24 @@ PySys_GetObject(const char *name)
     }
     PyObject *exc = _PyErr_GetRaisedException(tstate);
     PyObject *value;
-    (void) PyDict_GetItemStringRef(sysdict, name, &value);
+    int ret = PyDict_GetItemStringRef(sysdict, name, &value);
     /* XXX Suppress a new exception if it was raised and restore
      * the old one. */
     if (_PyErr_Occurred(tstate)) {
         PyErr_FormatUnraisable("Exception ignored in PySys_GetObject()");
     }
     _PyErr_SetRaisedException(tstate, exc);
     Py_XDECREF(value);  // return a borrowed reference
+#ifndef ABIFLAGS
+    if (ret == 0 && strcmp(name, "abiflags") == 0) {
+        if (PyErr_WarnEx(PyExc_DeprecationWarning,
+            "sys.abiflags will be set to a meaningful value "
+            "on all platforms in Python 3.16 instead of absent",
+            /*stack_level=*/1) < 0) {
+            return NULL;
+        }
+    }
+#endif
     return value;
 }