Re-add 3.13t in CI

* Split `cffi` depedency into two cases: 1.17 for versions up to 3.13, 2.0 for 3.14+
* Skip building cffi backend for 3.13t

Author: clin1234

.github/workflows/test.yml

@@ -117,6 +117,7 @@ jobs:
           pytest --numprocesses=auto --hypothesis-profile=${HYPOTHESIS_PROFILE} -v tests/
 
       - name: Test CFFI Backend
+        if: matrix.py != '3.13t'
         env:
           PYTHON_ZSTANDARD_IMPORT_POLICY: 'cffi'
         run: |

.github/workflows/wheel.yml

@@ -29,7 +29,9 @@ jobs:
           - 'cp311-cp311'
           - 'cp312-cp312'
           - 'cp313-cp313'
+          - 'cp313-cp313t'
           - 'cp314-cp314'
+          - 'cp313-cp314t'
         exclude:
           - image: 'musllinux_1_1_aarch64'
             py: 'cp314-cp314'

pyproject.toml

@@ -19,13 +19,17 @@ classifiers = [
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
     "Programming Language :: Python :: 3.14",
+    "Programming Language :: Python :: Free Threading :: 1 - Unstable",
+    "Programming Language :: Python :: Free Threading",
+
 ]
 keywords = ["zstandard", "zstd", "compression"]
 dependencies = []
 
 [project.optional-dependencies]
 cffi = [
-    'cffi>=2.0.0b1 ; python_version >= "3.13" and platform_python_implementation != "PyPy"',
+    "cffi~=1.17; platform_python_implementation != 'PyPy' and python_version < '3.14'",
+    "cffi>=2.0.0b; platform_python_implementation != 'PyPy' and python_version >= '3.14'",
 ]
 
 [project.urls]
@@ -34,7 +38,8 @@ Documentation = "https://python-zstandard.readthedocs.io/en/latest/"
 
 [build-system]
 requires = [
-    "cffi>=2.0.0b1 ; platform_python_implementation != 'PyPy'",
+    "cffi~=1.17; platform_python_implementation != 'PyPy' and python_version < '3.14'",
+    "cffi>=2.0.0b; platform_python_implementation != 'PyPy' and python_version >= '3.14'",
     "packaging",
     "setuptools",
 ]

setup.py

@@ -10,6 +10,7 @@
 import os
 import platform
 import sys
+import sysconfig
 
 from setuptools import setup
 
@@ -30,8 +31,8 @@
 # garbage collection pitfalls.
 # Require 1.17 everywhere so we don't have to think about supporting older
 # versions.
-# Require 2.0 for improved free-threading support
-MINIMUM_CFFI_VERSION = "2.0"
+# Require 2.0 for Python 3.14+ to add improved free-threading support
+MINIMUM_CFFI_VERSION = "2.0" if sys.version_info[0:2] >= (3, 14) else "1.17"
 
 ext_suffix = os.environ.get("SETUPTOOLS_EXT_SUFFIX")
 if ext_suffix:
@@ -90,6 +91,10 @@
 if platform.python_implementation() == "PyPy":
     C_BACKEND = False
 
+# cffi 2.0 only introduced no-GIL support for 3.14+.
+if platform.python_implementation() == "CPython" and sys.version_info[0:2] == (3, 13) and sysconfig.get_config_var("Py_GIL_DISABLED"):
+    CFFI_BACKEND = False
+
 if "--legacy" in sys.argv:
     SUPPORT_LEGACY = True
     sys.argv.remove("--legacy")