cython: freethreading_compatible (#654)

```
$ v3/bin/python -VV
Python 3.14.0 free-threading build (main, Oct  7 2025, 15:35:12) [Clang 20.1.4 ]

$ v3/bin/python -c 'import sys,msgpack; print(sys._is_gil_enabled())'
False
```

.github/workflows/test.yml

@@ -10,7 +10,7 @@ jobs:
     strategy:
       matrix:
         os: ["ubuntu-latest", "windows-latest", "windows-11-arm", "macos-latest"]
-        py: ["3.14-dev", "3.13", "3.12", "3.11", "3.10", "3.9"]
+        py: ["3.14", "3.14t", "3.13", "3.12", "3.11", "3.10", "3.9"]
         exclude:
           - os: windows-11-arm
             py: "3.9"

msgpack/_cmsgpack.pyx

@@ -1,5 +1,6 @@
-# coding: utf-8
 #cython: embedsignature=True, c_string_encoding=ascii, language_level=3
+#cython: freethreading_compatible = True
+import cython
 from cpython.datetime cimport import_datetime, datetime_new
 import_datetime()
 

msgpack/_packer.pyx

@@ -1,5 +1,3 @@
-# coding: utf-8
-
 from cpython cimport *
 from cpython.bytearray cimport PyByteArray_Check, PyByteArray_CheckExact
 from cpython.datetime cimport (
@@ -129,6 +127,7 @@ cdef class Packer:
         if self.exports > 0:
             raise BufferError("Existing exports of data: Packer cannot be changed")
 
+    @cython.critical_section
     def __init__(self, *, default=None,
                  bint use_single_float=False, bint autoreset=True, bint use_bin_type=True,
                  bint strict_types=False, bint datetime=False, unicode_errors=None,
@@ -269,6 +268,7 @@ cdef class Packer:
                 return ret
         return self._pack_inner(o, 0, nest_limit)
 
+    @cython.critical_section
     def pack(self, object obj):
         cdef int ret
         self._check_exports()
@@ -284,6 +284,7 @@ cdef class Packer:
             self.pk.length = 0
             return buf
 
+    @cython.critical_section
     def pack_ext_type(self, typecode, data):
         self._check_exports()
         if len(data) > ITEM_LIMIT:
@@ -291,6 +292,7 @@ cdef class Packer:
         msgpack_pack_ext(&self.pk, typecode, len(data))
         msgpack_pack_raw_body(&self.pk, data, len(data))
 
+    @cython.critical_section
     def pack_array_header(self, long long size):
         self._check_exports()
         if size > ITEM_LIMIT:
@@ -301,6 +303,7 @@ cdef class Packer:
             self.pk.length = 0
             return buf
 
+    @cython.critical_section
     def pack_map_header(self, long long size):
         self._check_exports()
         if size > ITEM_LIMIT:
@@ -311,6 +314,7 @@ cdef class Packer:
             self.pk.length = 0
             return buf
 
+    @cython.critical_section
     def pack_map_pairs(self, object pairs):
         """
         Pack *pairs* as msgpack map type.
@@ -331,6 +335,7 @@ cdef class Packer:
             self.pk.length = 0
             return buf
 
+    @cython.critical_section
     def reset(self):
         """Reset internal buffer.
 
@@ -339,6 +344,7 @@ cdef class Packer:
         self._check_exports()
         self.pk.length = 0
 
+    @cython.critical_section
     def bytes(self):
         """Return internal buffer contents as bytes object"""
         return PyBytes_FromStringAndSize(self.pk.buf, self.pk.length)

msgpack/_unpacker.pyx

@@ -1,5 +1,3 @@
-# coding: utf-8
-
 from cpython cimport *
 cdef extern from "Python.h":
     ctypedef struct PyObject
@@ -324,6 +322,7 @@ cdef class Unpacker:
         PyMem_Free(self.buf)
         self.buf = NULL
 
+    @cython.critical_section
     def __init__(self, file_like=None, *, Py_ssize_t read_size=0,
                  bint use_list=True, bint raw=False, int timestamp=0, bint strict_map_key=True,
                  object object_hook=None, object object_pairs_hook=None, object list_hook=None,
@@ -384,6 +383,7 @@ cdef class Unpacker:
                  max_str_len, max_bin_len, max_array_len,
                  max_map_len, max_ext_len)
 
+    @cython.critical_section
     def feed(self, object next_bytes):
         """Append `next_bytes` to internal buffer."""
         cdef Py_buffer pybuff
@@ -484,6 +484,7 @@ cdef class Unpacker:
             else:
                 raise ValueError("Unpack failed: error = %d" % (ret,))
 
+    @cython.critical_section
     def read_bytes(self, Py_ssize_t nbytes):
         """Read a specified number of raw bytes from the stream"""
         cdef Py_ssize_t nread
@@ -496,6 +497,7 @@ cdef class Unpacker:
         self.stream_offset += nread
         return ret
 
+    @cython.critical_section
     def unpack(self):
         """Unpack one object
 
@@ -503,6 +505,7 @@ cdef class Unpacker:
         """
         return self._unpack(unpack_construct)
 
+    @cython.critical_section
     def skip(self):
         """Read and ignore one object, returning None
 
@@ -510,6 +513,7 @@ cdef class Unpacker:
         """
         return self._unpack(unpack_skip)
 
+    @cython.critical_section
     def read_array_header(self):
         """assuming the next object is an array, return its size n, such that
         the next n unpack() calls will iterate over its contents.
@@ -518,6 +522,7 @@ cdef class Unpacker:
         """
         return self._unpack(read_array_header)
 
+    @cython.critical_section
     def read_map_header(self):
         """assuming the next object is a map, return its size n, such that the
         next n * 2 unpack() calls will iterate over its key-value pairs.
@@ -526,6 +531,7 @@ cdef class Unpacker:
         """
         return self._unpack(read_map_header)
 
+    @cython.critical_section
     def tell(self):
         """Returns the current position of the Unpacker in bytes, i.e., the
         number of bytes that were read from the input, also the starting
@@ -536,6 +542,7 @@ cdef class Unpacker:
     def __iter__(self):
         return self
 
+    @cython.critical_section
     def __next__(self):
         return self._unpack(unpack_construct, 1)