[pull] main from python:main

.github/workflows/build.yml

@@ -15,7 +15,13 @@ permissions:
   contents: read
 
 concurrency:
-  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}-reusable
+  # https://docs.github.com/en/actions/writing-workflows/workflow-syntax-for-github-actions#concurrency
+  # 'group' must be a key uniquely representing a PR or push event.
+  # github.workflow is the workflow name
+  # github.actor is the user invoking the workflow
+  # github.head_ref is the source branch of the PR or otherwise blank
+  # github.run_id is a unique number for the current run
+  group: ${{ github.workflow }}-${{ github.actor }}-${{ github.head_ref || github.run_id }}
   cancel-in-progress: true
 
 env:

Doc/howto/isolating-extensions.rst

@@ -215,21 +215,36 @@ multiple interpreters correctly. If this is not yet the case for your
 module, you can explicitly make your module loadable only once per
 process. For example::
 
+   // A process-wide flag
    static int loaded = 0;
 
+   // Mutex to provide thread safety (only needed for free-threaded Python)
+   static PyMutex modinit_mutex = {0};
+
    static int
    exec_module(PyObject* module)
    {
+       PyMutex_Lock(&modinit_mutex);
        if (loaded) {
+           PyMutex_Unlock(&modinit_mutex);
            PyErr_SetString(PyExc_ImportError,
                            "cannot load module more than once per process");
            return -1;
        }
        loaded = 1;
+       PyMutex_Unlock(&modinit_mutex);
        // ... rest of initialization
    }
 
 
+If your module's :c:member:`PyModuleDef.m_clear` function is able to prepare
+for future re-initialization, it should clear the ``loaded`` flag.
+In this case, your module won't support multiple instances existing
+*concurrently*, but it will, for example, support being loaded after
+Python runtime shutdown (:c:func:`Py_FinalizeEx`) and re-initialization
+(:c:func:`Py_Initialize`).
+
+
 Module State Access from Functions
 ----------------------------------
 

Include/internal/pycore_stackref.h

@@ -238,6 +238,7 @@ PyStackRef_IsNullOrInt(_PyStackRef ref);
 #else
 
 #define Py_INT_TAG 3
+#define Py_TAG_REFCNT 1
 
 static inline bool
 PyStackRef_IsTaggedInt(_PyStackRef i)
@@ -263,7 +264,7 @@ PyStackRef_UntagInt(_PyStackRef i)
 
 #ifdef Py_GIL_DISABLED
 
-#define Py_TAG_DEFERRED (1)
+#define Py_TAG_DEFERRED Py_TAG_REFCNT
 
 #define Py_TAG_PTR      ((uintptr_t)0)
 #define Py_TAG_BITS     ((uintptr_t)1)
@@ -441,14 +442,13 @@ PyStackRef_AsStrongReference(_PyStackRef stackref)
 /* References to immortal objects always have their tag bit set to Py_TAG_REFCNT
  * as they can (must) have their reclamation deferred */
 
-#define Py_TAG_BITS 1
-#define Py_TAG_REFCNT 1
+#define Py_TAG_BITS 3
 #if _Py_IMMORTAL_FLAGS != Py_TAG_REFCNT
 #  error "_Py_IMMORTAL_FLAGS != Py_TAG_REFCNT"
 #endif
 
 #define BITS_TO_PTR(REF) ((PyObject *)((REF).bits))
-#define BITS_TO_PTR_MASKED(REF) ((PyObject *)(((REF).bits) & (~Py_TAG_BITS)))
+#define BITS_TO_PTR_MASKED(REF) ((PyObject *)(((REF).bits) & (~Py_TAG_REFCNT)))
 
 #define PyStackRef_NULL_BITS Py_TAG_REFCNT
 static const _PyStackRef PyStackRef_NULL = { .bits = PyStackRef_NULL_BITS };
@@ -528,7 +528,7 @@ PyStackRef_FromPyObjectSteal(PyObject *obj)
 {
     assert(obj != NULL);
 #if SIZEOF_VOID_P > 4
-    unsigned int tag = obj->ob_flags & Py_TAG_BITS;
+    unsigned int tag = obj->ob_flags & Py_TAG_REFCNT;
 #else
     unsigned int tag = _Py_IsImmortal(obj) ? Py_TAG_REFCNT : 0;
 #endif
@@ -547,12 +547,6 @@ PyStackRef_FromPyObjectStealMortal(PyObject *obj)
     return ref;
 }
 
-// Check if a stackref is exactly the same as another stackref, including the
-// the deferred bit. This can only be used safely if you know that the deferred
-// bits of `a` and `b` match.
-#define PyStackRef_IsExactly(a, b) \
-    (assert(((a).bits & Py_TAG_BITS) == ((b).bits & Py_TAG_BITS)), (a).bits == (b).bits)
-
 static inline _PyStackRef
 _PyStackRef_FromPyObjectNew(PyObject *obj)
 {
@@ -604,7 +598,7 @@ PyStackRef_DUP(_PyStackRef ref)
 static inline bool
 PyStackRef_IsHeapSafe(_PyStackRef ref)
 {
-    return (ref.bits & Py_TAG_BITS) == 0 || ref.bits == PyStackRef_NULL_BITS ||  _Py_IsImmortal(BITS_TO_PTR_MASKED(ref));
+    return (ref.bits & Py_TAG_BITS) != Py_TAG_REFCNT || ref.bits == PyStackRef_NULL_BITS ||  _Py_IsImmortal(BITS_TO_PTR_MASKED(ref));
 }
 
 static inline _PyStackRef
@@ -679,7 +673,7 @@ PyStackRef_XCLOSE(_PyStackRef ref)
 
 // Note: this is a macro because MSVC (Windows) has trouble inlining it.
 
-#define PyStackRef_Is(a, b) (((a).bits & (~Py_TAG_BITS)) == ((b).bits & (~Py_TAG_BITS)))
+#define PyStackRef_Is(a, b) (((a).bits & (~Py_TAG_REFCNT)) == ((b).bits & (~Py_TAG_REFCNT)))
 
 
 #endif // !defined(Py_GIL_DISABLED) && defined(Py_STACKREF_DEBUG)

Lib/test/test_capi/test_bytearray.py

@@ -66,6 +66,7 @@ def test_fromobject(self):
         # Test PyByteArray_FromObject()
         fromobject = _testlimitedcapi.bytearray_fromobject
 
+        self.assertEqual(fromobject(b''), bytearray(b''))
         self.assertEqual(fromobject(b'abc'), bytearray(b'abc'))
         self.assertEqual(fromobject(bytearray(b'abc')), bytearray(b'abc'))
         self.assertEqual(fromobject(ByteArraySubclass(b'abc')), bytearray(b'abc'))
@@ -115,6 +116,7 @@ def test_concat(self):
         self.assertEqual(concat(b'abc', bytearray(b'def')), bytearray(b'abcdef'))
         self.assertEqual(concat(bytearray(b'abc'), b''), bytearray(b'abc'))
         self.assertEqual(concat(b'', bytearray(b'def')), bytearray(b'def'))
+        self.assertEqual(concat(bytearray(b''), bytearray(b'')), bytearray(b''))
         self.assertEqual(concat(memoryview(b'xabcy')[1:4], b'def'),
                          bytearray(b'abcdef'))
         self.assertEqual(concat(b'abc', memoryview(b'xdefy')[1:4]),
@@ -150,6 +152,10 @@ def test_resize(self):
         self.assertEqual(resize(ba, 0), 0)
         self.assertEqual(ba, bytearray())
 
+        ba = bytearray(b'')
+        self.assertEqual(resize(ba, 0), 0)
+        self.assertEqual(ba, bytearray())
+
         ba = ByteArraySubclass(b'abcdef')
         self.assertEqual(resize(ba, 3), 0)
         self.assertEqual(ba, bytearray(b'abc'))

Lib/test/test_capi/test_bytes.py

@@ -81,6 +81,7 @@ def test_fromobject(self):
         # Test PyBytes_FromObject()
         fromobject = _testlimitedcapi.bytes_fromobject
 
+        self.assertEqual(fromobject(b''), b'')
         self.assertEqual(fromobject(b'abc'), b'abc')
         self.assertEqual(fromobject(bytearray(b'abc')), b'abc')
         self.assertEqual(fromobject(BytesSubclass(b'abc')), b'abc')
@@ -138,6 +139,7 @@ def test_repr(self):
         # Test PyBytes_Repr()
         bytes_repr = _testlimitedcapi.bytes_repr
 
+        self.assertEqual(bytes_repr(b'', 0), r"""b''""")
         self.assertEqual(bytes_repr(b'''abc''', 0), r"""b'abc'""")
         self.assertEqual(bytes_repr(b'''abc''', 1), r"""b'abc'""")
         self.assertEqual(bytes_repr(b'''a'b"c"d''', 0), r"""b'a\'b"c"d'""")
@@ -197,6 +199,7 @@ def test_decodeescape(self):
         """Test PyBytes_DecodeEscape()"""
         decodeescape = _testlimitedcapi.bytes_decodeescape
 
+        self.assertEqual(decodeescape(b''), b'')
         self.assertEqual(decodeescape(b'abc'), b'abc')
         self.assertEqual(decodeescape(br'\t\n\r\x0b\x0c\x00\\\'\"'),
                          b'''\t\n\r\v\f\0\\'"''')

Tools/cases_generator/analyzer.py

@@ -832,7 +832,7 @@ def compute_properties(op: parser.CodeDef) -> Properties:
         )
     error_with_pop = has_error_with_pop(op)
     error_without_pop = has_error_without_pop(op)
-    escapes = bool(escaping_calls)
+    escapes = bool(escaping_calls) or variable_used(op, "DECREF_INPUTS")
     pure = False if isinstance(op, parser.LabelDef) else "pure" in op.annotations
     no_save_ip = False if isinstance(op, parser.LabelDef) else "no_save_ip" in op.annotations
     return Properties(