hard disable Py_LIMITED_API for free-threaded builds (#125)

* all Linux x86_64 tests pass on 3.13t_x86_64 as of 3.13.0rc2
* update some broken test assumptions around limited API support and eager global GC
* add non-artifact CI job for 3.13t

.github/workflows/ci.yaml

@@ -83,6 +83,9 @@ jobs:
             omit: ${{ env.skip_ci_redundant_jobs }}
 
           - spec: cp313-manylinux_x86_64
+            
+          - spec: cp313t-manylinux_x86_64
+            skip_artifact_upload: 'true'
   
           - spec: cp38-manylinux_i686
             omit: ${{ env.skip_ci_redundant_jobs }}
@@ -290,6 +293,7 @@ jobs:
         CIBW_MUSLLINUX_I686_IMAGE: ${{ matrix.musllinux_img || 'musllinux_1_1' }}
         CIBW_MUSLLINUX_AARCH64_IMAGE: ${{ matrix.musllinux_img || 'musllinux_1_1' }}
         CIBW_PRERELEASE_PYTHONS: 'True'
+        CIBW_FREE_THREADED_SUPPORT: 'True'
         CIBW_TEST_REQUIRES: pytest setuptools  # 3.12+ no longer includes distutils, just always ensure setuptools is present
         CIBW_TEST_COMMAND: PYTHONUNBUFFERED=1 python -m pytest ${{ matrix.test_args || '{project}' }}  # default to test all
       run: |
@@ -311,7 +315,7 @@ jobs:
         name: ${{ steps.build.outputs.artifact_name }}
         path: dist/*.whl
         if-no-files-found: error
-      if: ${{ env.skip_artifact_upload != 'true' }}
+      if: ${{ (matrix.skip_artifact_upload != 'true') && (env.skip_artifact_upload != 'true') }}
 
   make_macos_matrix:
     runs-on: ubuntu-22.04

src/cffi/recompiler.py

@@ -1,4 +1,4 @@
-import os, sys, io
+import io, os, sys, sysconfig
 from . import ffiplatform, model
 from .error import VerificationError
 from .cffi_opcode import *
@@ -7,9 +7,9 @@
 VERSION_EMBEDDED = 0x2701
 VERSION_CHAR16CHAR32 = 0x2801
 
-USE_LIMITED_API = (sys.platform != 'win32' or sys.version_info < (3, 0) or
-                   sys.version_info >= (3, 5))
-
+USE_LIMITED_API = ((sys.platform != 'win32' or sys.version_info < (3, 0) or
+                   sys.version_info >= (3, 5)) and
+                   not sysconfig.get_config_var("Py_GIL_DISABLED"))  # free-threaded doesn't yet support limited API
 
 class GlobalExpr:
     def __init__(self, name, address, type_op, size=0, check_value=0):

src/cffi/setuptools_ext.py

@@ -1,5 +1,6 @@
 import os
 import sys
+import sysconfig
 
 try:
     basestring
@@ -87,6 +88,7 @@ def _set_py_limited_api(Extension, kwds):
     Recently (2020) we started shipping only >= 3.5 wheels, though.  So
     we'll give it another try and set py_limited_api on Windows >= 3.5.
     """
+    from cffi._shimmed_dist_utils import log
     from cffi import recompiler
 
     if ('py_limited_api' not in kwds and not hasattr(sys, 'gettotalrefcount')
@@ -102,6 +104,12 @@ def _set_py_limited_api(Extension, kwds):
             # warning.
             kwds['py_limited_api'] = True
 
+    if sysconfig.get_config_var("Py_GIL_DISABLED"):
+        if kwds.get('py_limited_api'):
+            log.info("Ignoring py_limited_api=True for free-threaded build.")
+
+        kwds['py_limited_api'] = False
+
     if kwds.get('py_limited_api') is False:
         # avoid setting Py_LIMITED_API if py_limited_api=False
         # which _cffi_include.h does unless _CFFI_NO_LIMITED_API is defined

testing/cffi0/test_zintegration.py

@@ -1,5 +1,6 @@
 import py, os, sys, shutil
 import subprocess
+import sysconfig
 import textwrap
 from testing.udir import udir
 import pytest
@@ -179,7 +180,8 @@ def test_set_py_limited_api(self):
         except ImportError as e:
             pytest.skip(str(e))
         orig_version = setuptools.__version__
-        expecting_limited_api = not hasattr(sys, 'gettotalrefcount')
+        # free-threaded Python does not yet support limited API
+        expecting_limited_api = not hasattr(sys, 'gettotalrefcount') and not sysconfig.get_config_var("Py_GIL_DISABLED")
         try:
             setuptools.__version__ = '26.0.0'
             from setuptools import Extension

testing/cffi1/test_ffi_obj.py

@@ -35,16 +35,17 @@ def test_ffi_cache_type():
 def test_ffi_type_not_immortal():
     import weakref, gc
     ffi = _cffi1_backend.FFI()
-    t1 = ffi.typeof("int **")
-    t2 = ffi.typeof("int *")
+    # this test can fail on free-threaded builds lazier GC if the type was used by another test
+    t1 = ffi.typeof("unsigned short int **")
+    t2 = ffi.typeof("unsigned short int *")
     w1 = weakref.ref(t1)
     w2 = weakref.ref(t2)
     del t1, ffi
     gc.collect()
     assert w1() is None
     assert w2() is t2
     ffi = _cffi1_backend.FFI()
-    assert ffi.typeof(ffi.new("int **")[0]) is t2
+    assert ffi.typeof(ffi.new("unsigned short int **")[0]) is t2
     #
     ffi = _cffi1_backend.FFI()
     t1 = ffi.typeof("int ***")