diff --git a/newsfragments/4478.feature.rst b/newsfragments/4478.feature.rst
new file mode 100644
index 0000000000..bd53339464
--- /dev/null
+++ b/newsfragments/4478.feature.rst
@@ -0,0 +1 @@
+Synced with pypa/distutils@c97a3db2f including better support for free threaded Python on Windows (pypa/distutils#310), improved typing support, and linter accommodations.
diff --git a/pyproject.toml b/pyproject.toml
index a19d4ac164..643b59591a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -102,7 +102,7 @@ core = [
 
 	# for distutils
 	"jaraco.collections",
-	"jaraco.functools>=4",
+	"jaraco.functools >= 4",
 	"packaging",
 	"more_itertools",
 ]
diff --git a/setuptools/_distutils/cmd.py b/setuptools/_distutils/cmd.py
index 2bb97956ab..9c6fa6566c 100644
--- a/setuptools/_distutils/cmd.py
+++ b/setuptools/_distutils/cmd.py
@@ -4,15 +4,21 @@
 in the distutils.command package.
 """
 
+from __future__ import annotations
+
 import logging
 import os
 import re
 import sys
+from collections.abc import Callable
+from typing import Any, ClassVar, TypeVar, overload
 
 from . import _modified, archive_util, dir_util, file_util, util
 from ._log import log
 from .errors import DistutilsOptionError
 
+_CommandT = TypeVar("_CommandT", bound="Command")
+
 
 class Command:
     """Abstract base class for defining command classes, the "worker bees"
@@ -44,7 +50,14 @@ class Command:
     # 'sub_commands' is usually defined at the *end* of a class, because
     # predicates can be unbound methods, so they must already have been
     # defined.  The canonical example is the "install" command.
-    sub_commands = []
+    sub_commands: ClassVar[  # Any to work around variance issues
+        list[tuple[str, Callable[[Any], bool] | None]]
+    ] = []
+
+    user_options: ClassVar[
+        # Specifying both because list is invariant. Avoids mypy override assignment issues
+        list[tuple[str, str, str]] | list[tuple[str, str | None, str]]
+    ] = []
 
     # -- Creation/initialization methods -------------------------------
 
@@ -305,7 +318,17 @@ def get_finalized_command(self, command, create=True):
 
     # XXX rename to 'get_reinitialized_command()'? (should do the
     # same in dist.py, if so)
-    def reinitialize_command(self, command, reinit_subcommands=False):
+    @overload
+    def reinitialize_command(
+        self, command: str, reinit_subcommands: bool = False
+    ) -> Command: ...
+    @overload
+    def reinitialize_command(
+        self, command: _CommandT, reinit_subcommands: bool = False
+    ) -> _CommandT: ...
+    def reinitialize_command(
+        self, command: str | Command, reinit_subcommands=False
+    ) -> Command:
         return self.distribution.reinitialize_command(command, reinit_subcommands)
 
     def run_command(self, command):
diff --git a/setuptools/_distutils/command/bdist.py b/setuptools/_distutils/command/bdist.py
index f334075159..1ec3c35f40 100644
--- a/setuptools/_distutils/command/bdist.py
+++ b/setuptools/_distutils/command/bdist.py
@@ -5,6 +5,7 @@
 
 import os
 import warnings
+from typing import ClassVar
 
 from ..core import Command
 from ..errors import DistutilsOptionError, DistutilsPlatformError
@@ -23,7 +24,7 @@ def show_formats():
     pretty_printer.print_help("List of available distribution formats:")
 
 
-class ListCompat(dict):
+class ListCompat(dict[str, tuple[str, str]]):
     # adapter to allow for Setuptools compatibility in format_commands
     def append(self, item):
         warnings.warn(
@@ -70,7 +71,7 @@ class bdist(Command):
     ]
 
     # The following commands do not take a format option from bdist
-    no_format_option = ('bdist_rpm',)
+    no_format_option: ClassVar[tuple[str, ...]] = ('bdist_rpm',)
 
     # This won't do in reality: will need to distinguish RPM-ish Linux,
     # Debian-ish Linux, Solaris, FreeBSD, ..., Windows, Mac OS.
diff --git a/setuptools/_distutils/command/build.py b/setuptools/_distutils/command/build.py
index caf55073af..ccd2c706a3 100644
--- a/setuptools/_distutils/command/build.py
+++ b/setuptools/_distutils/command/build.py
@@ -113,7 +113,8 @@ def finalize_options(self):  # noqa: C901
             self.build_temp = os.path.join(self.build_base, 'temp' + plat_specifier)
         if self.build_scripts is None:
             self.build_scripts = os.path.join(
-                self.build_base, 'scripts-%d.%d' % sys.version_info[:2]
+                self.build_base,
+                f'scripts-{sys.version_info.major}.{sys.version_info.minor}',
             )
 
         if self.executable is None and sys.executable:
diff --git a/setuptools/_distutils/command/build_clib.py b/setuptools/_distutils/command/build_clib.py
index a600d09373..3e1832768b 100644
--- a/setuptools/_distutils/command/build_clib.py
+++ b/setuptools/_distutils/command/build_clib.py
@@ -16,6 +16,7 @@
 
 import os
 from distutils._log import log
+from typing import ClassVar
 
 from ..core import Command
 from ..errors import DistutilsSetupError
@@ -31,7 +32,7 @@ def show_compilers():
 class build_clib(Command):
     description = "build C/C++ libraries used by Python extensions"
 
-    user_options = [
+    user_options: ClassVar[list[tuple[str, str, str]]] = [
         ('build-clib=', 'b', "directory to build C/C++ libraries to"),
         ('build-temp=', 't', "directory to put temporary build by-products"),
         ('debug', 'g', "compile with debugging information"),
@@ -138,8 +139,7 @@ def check_library_list(self, libraries):
 
             if '/' in name or (os.sep != '/' and os.sep in name):
                 raise DistutilsSetupError(
-                    f"bad library name '{lib[0]}': "
-                    "may not contain directory separators"
+                    f"bad library name '{lib[0]}': may not contain directory separators"
                 )
 
             if not isinstance(build_info, dict):
diff --git a/setuptools/_distutils/command/build_ext.py b/setuptools/_distutils/command/build_ext.py
index a7e3038be6..cf60bd0ad8 100644
--- a/setuptools/_distutils/command/build_ext.py
+++ b/setuptools/_distutils/command/build_ext.py
@@ -23,7 +23,7 @@
 )
 from ..extension import Extension
 from ..sysconfig import customize_compiler, get_config_h_filename, get_python_version
-from ..util import get_platform, is_mingw
+from ..util import get_platform, is_freethreaded, is_mingw
 
 # An extension name is just a dot-separated list of Python NAMEs (ie.
 # the same as a fully-qualified module name).
@@ -333,6 +333,12 @@ def run(self):  # noqa: C901
         if os.name == 'nt' and self.plat_name != get_platform():
             self.compiler.initialize(self.plat_name)
 
+        # The official Windows free threaded Python installer doesn't set
+        # Py_GIL_DISABLED because its pyconfig.h is shared with the
+        # default build, so define it here (pypa/setuptools#4662).
+        if os.name == 'nt' and is_freethreaded():
+            self.compiler.define_macro('Py_GIL_DISABLED', '1')
+
         # And make sure that any compile/link-related options (which might
         # come from the command-line or from the setup script) are set in
         # that CCompiler object -- that way, they automatically apply to
@@ -437,8 +443,7 @@ def check_extensions_list(self, extensions):  # noqa: C901
                 for macro in macros:
                     if not (isinstance(macro, tuple) and len(macro) in (1, 2)):
                         raise DistutilsSetupError(
-                            "'macros' element of build info dict "
-                            "must be 1- or 2-tuple"
+                            "'macros' element of build info dict must be 1- or 2-tuple"
                         )
                     if len(macro) == 1:
                         ext.undef_macros.append(macro[0])
@@ -666,8 +671,7 @@ def find_swig(self):
                 return "swig.exe"
         else:
             raise DistutilsPlatformError(
-                "I don't know how to find (much less run) SWIG "
-                f"on platform '{os.name}'"
+                f"I don't know how to find (much less run) SWIG on platform '{os.name}'"
             )
 
     # -- Name generators -----------------------------------------------
diff --git a/setuptools/_distutils/command/build_scripts.py b/setuptools/_distutils/command/build_scripts.py
index 9e5963c243..1c6fd3caff 100644
--- a/setuptools/_distutils/command/build_scripts.py
+++ b/setuptools/_distutils/command/build_scripts.py
@@ -8,6 +8,7 @@
 from distutils import sysconfig
 from distutils._log import log
 from stat import ST_MODE
+from typing import ClassVar
 
 from .._modified import newer
 from ..core import Command
@@ -25,7 +26,7 @@
 class build_scripts(Command):
     description = "\"build\" scripts (copy and fixup #! line)"
 
-    user_options = [
+    user_options: ClassVar[list[tuple[str, str, str]]] = [
         ('build-dir=', 'd', "directory to \"build\" (copy) to"),
         ('force', 'f', "forcibly build everything (ignore file timestamps"),
         ('executable=', 'e', "specify final destination interpreter path"),
diff --git a/setuptools/_distutils/command/check.py b/setuptools/_distutils/command/check.py
index 93d754e73d..078c1ce87e 100644
--- a/setuptools/_distutils/command/check.py
+++ b/setuptools/_distutils/command/check.py
@@ -4,6 +4,7 @@
 """
 
 import contextlib
+from typing import ClassVar
 
 from ..core import Command
 from ..errors import DistutilsSetupError
@@ -41,15 +42,12 @@ class check(Command):
     """This command checks the meta-data of the package."""
 
     description = "perform some checks on the package"
-    user_options = [
+    user_options: ClassVar[list[tuple[str, str, str]]] = [
         ('metadata', 'm', 'Verify meta-data'),
         (
             'restructuredtext',
             'r',
-            (
-                'Checks if long string meta-data syntax '
-                'are reStructuredText-compliant'
-            ),
+            'Checks if long string meta-data syntax are reStructuredText-compliant',
         ),
         ('strict', 's', 'Will exit with an error if a check fails'),
     ]
diff --git a/setuptools/_distutils/command/command_template b/setuptools/_distutils/command/command_template
index 6106819db8..a4a751ad3c 100644
--- a/setuptools/_distutils/command/command_template
+++ b/setuptools/_distutils/command/command_template
@@ -8,18 +8,18 @@ Implements the Distutils 'x' command.
 __revision__ = "$Id$"
 
 from distutils.core import Command
+from typing import ClassVar
 
 
 class x(Command):
-
     # Brief (40-50 characters) description of the command
     description = ""
 
     # List of option tuples: long name, short name (None if no short
     # name), and help string.
-    user_options = [('', '',
-                     ""),
-                   ]
+    user_options: ClassVar[list[tuple[str, str, str]]] = [
+        ('', '', ""),
+    ]
 
     def initialize_options(self):
         self. = None
diff --git a/setuptools/_distutils/command/install.py b/setuptools/_distutils/command/install.py
index ceb453e041..9400995024 100644
--- a/setuptools/_distutils/command/install.py
+++ b/setuptools/_distutils/command/install.py
@@ -407,8 +407,8 @@ def finalize_options(self):  # noqa: C901
             'dist_version': self.distribution.get_version(),
             'dist_fullname': self.distribution.get_fullname(),
             'py_version': py_version,
-            'py_version_short': '%d.%d' % sys.version_info[:2],
-            'py_version_nodot': '%d%d' % sys.version_info[:2],
+            'py_version_short': f'{sys.version_info.major}.{sys.version_info.minor}',
+            'py_version_nodot': f'{sys.version_info.major}{sys.version_info.minor}',
             'sys_prefix': prefix,
             'prefix': prefix,
             'sys_exec_prefix': exec_prefix,
diff --git a/setuptools/_distutils/command/install_data.py b/setuptools/_distutils/command/install_data.py
index a90ec3b4d0..36f5bcc8bf 100644
--- a/setuptools/_distutils/command/install_data.py
+++ b/setuptools/_distutils/command/install_data.py
@@ -9,7 +9,7 @@
 
 import functools
 import os
-from typing import Iterable
+from collections.abc import Iterable
 
 from ..core import Command
 from ..util import change_root, convert_path
@@ -22,8 +22,7 @@ class install_data(Command):
         (
             'install-dir=',
             'd',
-            "base directory for installing data files "
-            "[default: installation base dir]",
+            "base directory for installing data files [default: installation base dir]",
         ),
         ('root=', None, "install everything relative to this alternate root directory"),
         ('force', 'f', "force installation (overwrite existing files)"),
diff --git a/setuptools/_distutils/command/install_egg_info.py b/setuptools/_distutils/command/install_egg_info.py
index 4fbb3440ab..230e94ab46 100644
--- a/setuptools/_distutils/command/install_egg_info.py
+++ b/setuptools/_distutils/command/install_egg_info.py
@@ -8,6 +8,7 @@
 import os
 import re
 import sys
+from typing import ClassVar
 
 from .. import dir_util
 from .._log import log
@@ -18,7 +19,7 @@ class install_egg_info(Command):
     """Install an .egg-info file for the package"""
 
     description = "Install package's PKG-INFO metadata as an .egg-info file"
-    user_options = [
+    user_options: ClassVar[list[tuple[str, str, str]]] = [
         ('install-dir=', 'd', "directory to install to"),
     ]
 
@@ -31,11 +32,9 @@ def basename(self):
         Allow basename to be overridden by child class.
         Ref pypa/distutils#2.
         """
-        return "%s-%s-py%d.%d.egg-info" % (
-            to_filename(safe_name(self.distribution.get_name())),
-            to_filename(safe_version(self.distribution.get_version())),
-            *sys.version_info[:2],
-        )
+        name = to_filename(safe_name(self.distribution.get_name()))
+        version = to_filename(safe_version(self.distribution.get_version()))
+        return f"{name}-{version}-py{sys.version_info.major}.{sys.version_info.minor}.egg-info"
 
     def finalize_options(self):
         self.set_undefined_options('install_lib', ('install_dir', 'install_dir'))
diff --git a/setuptools/_distutils/command/install_headers.py b/setuptools/_distutils/command/install_headers.py
index fbb3b242ea..586121e089 100644
--- a/setuptools/_distutils/command/install_headers.py
+++ b/setuptools/_distutils/command/install_headers.py
@@ -3,6 +3,8 @@
 Implements the Distutils 'install_headers' command, to install C/C++ header
 files to the Python include directory."""
 
+from typing import ClassVar
+
 from ..core import Command
 
 
@@ -10,7 +12,7 @@
 class install_headers(Command):
     description = "install C/C++ header files"
 
-    user_options = [
+    user_options: ClassVar[list[tuple[str, str, str]]] = [
         ('install-dir=', 'd', "directory to install header files to"),
         ('force', 'f', "force installation (overwrite existing files)"),
     ]
diff --git a/setuptools/_distutils/command/sdist.py b/setuptools/_distutils/command/sdist.py
index d723a1c9fb..acb3a41650 100644
--- a/setuptools/_distutils/command/sdist.py
+++ b/setuptools/_distutils/command/sdist.py
@@ -8,6 +8,7 @@
 from distutils._log import log
 from glob import glob
 from itertools import filterfalse
+from typing import ClassVar
 
 from ..core import Command
 from ..errors import DistutilsOptionError, DistutilsTemplateError
@@ -114,7 +115,7 @@ def checking_metadata(self):
 
     sub_commands = [('check', checking_metadata)]
 
-    READMES = ('README', 'README.txt', 'README.rst')
+    READMES: ClassVar[tuple[str, ...]] = ('README', 'README.txt', 'README.rst')
 
     def initialize_options(self):
         # 'template' and 'manifest' are, respectively, the names of
@@ -362,8 +363,7 @@ def read_template(self):
                 # convert_path function
                 except (DistutilsTemplateError, ValueError) as msg:
                     self.warn(
-                        "%s, line %d: %s"
-                        % (template.filename, template.current_line, msg)
+                        f"{template.filename}, line {int(template.current_line)}: {msg}"
                     )
         finally:
             template.close()
diff --git a/setuptools/_distutils/compat/__init__.py b/setuptools/_distutils/compat/__init__.py
index e12534a32c..c715ee9cc5 100644
--- a/setuptools/_distutils/compat/__init__.py
+++ b/setuptools/_distutils/compat/__init__.py
@@ -1,7 +1,5 @@
 from __future__ import annotations
 
-from .py38 import removeprefix
-
 
 def consolidate_linker_args(args: list[str]) -> list[str] | str:
     """
@@ -12,4 +10,4 @@ def consolidate_linker_args(args: list[str]) -> list[str] | str:
 
     if not all(arg.startswith('-Wl,') for arg in args):
         return args
-    return '-Wl,' + ','.join(removeprefix(arg, '-Wl,') for arg in args)
+    return '-Wl,' + ','.join(arg.removeprefix('-Wl,') for arg in args)
diff --git a/setuptools/_distutils/compat/py38.py b/setuptools/_distutils/compat/py38.py
deleted file mode 100644
index afe5345553..0000000000
--- a/setuptools/_distutils/compat/py38.py
+++ /dev/null
@@ -1,34 +0,0 @@
-import sys
-
-if sys.version_info < (3, 9):
-
-    def removesuffix(self, suffix):
-        # suffix='' should not call self[:-0].
-        if suffix and self.endswith(suffix):
-            return self[: -len(suffix)]
-        else:
-            return self[:]
-
-    def removeprefix(self, prefix):
-        if self.startswith(prefix):
-            return self[len(prefix) :]
-        else:
-            return self[:]
-
-else:
-
-    def removesuffix(self, suffix):
-        return self.removesuffix(suffix)
-
-    def removeprefix(self, prefix):
-        return self.removeprefix(prefix)
-
-
-def aix_platform(osname, version, release):
-    try:
-        import _aix_support
-
-        return _aix_support.aix_platform()
-    except ImportError:
-        pass
-    return f"{osname}-{version}.{release}"
diff --git a/setuptools/_distutils/core.py b/setuptools/_distutils/core.py
index bc06091abb..bd62546bdd 100644
--- a/setuptools/_distutils/core.py
+++ b/setuptools/_distutils/core.py
@@ -6,9 +6,12 @@
 really defined in distutils.dist and distutils.cmd.
 """
 
+from __future__ import annotations
+
 import os
 import sys
 import tokenize
+from collections.abc import Iterable
 
 from .cmd import Command
 from .debug import DEBUG
@@ -215,7 +218,7 @@ def run_commands(dist):
     return dist
 
 
-def run_setup(script_name, script_args=None, stop_after="run"):
+def run_setup(script_name, script_args: Iterable[str] | None = None, stop_after="run"):
     """Run a setup script in a somewhat controlled environment, and
     return the Distribution instance that drives things.  This is useful
     if you need to find out the distribution meta-data (passed as
diff --git a/setuptools/_distutils/dist.py b/setuptools/_distutils/dist.py
index 154301baff..33ed8ebd7a 100644
--- a/setuptools/_distutils/dist.py
+++ b/setuptools/_distutils/dist.py
@@ -4,6 +4,8 @@
 being built/installed/distributed.
 """
 
+from __future__ import annotations
+
 import contextlib
 import logging
 import os
@@ -13,6 +15,7 @@
 import warnings
 from collections.abc import Iterable
 from email import message_from_file
+from typing import TYPE_CHECKING, Literal, TypeVar, overload
 
 from packaging.utils import canonicalize_name, canonicalize_version
 
@@ -27,6 +30,12 @@
 from .fancy_getopt import FancyGetopt, translate_longopt
 from .util import check_environ, rfc822_escape, strtobool
 
+if TYPE_CHECKING:
+    # type-only import because of mutual dependence between these modules
+    from .cmd import Command
+
+_CommandT = TypeVar("_CommandT", bound="Command")
+
 # Regex to define acceptable Distutils command names.  This is not *quite*
 # the same as a Python NAME -- I don't allow leading underscores.  The fact
 # that they're very similar is no coincidence; the default naming scheme is
@@ -139,7 +148,7 @@ def __init__(self, attrs=None):  # noqa: C901
         self.dry_run = False
         self.help = False
         for attr in self.display_option_names:
-            setattr(self, attr, 0)
+            setattr(self, attr, False)
 
         # Store the distribution meta-data (name, version, author, and so
         # forth) in a separate object -- we're getting to have enough
@@ -169,7 +178,7 @@ def __init__(self, attrs=None):  # noqa: C901
         # and sys.argv[1:], but they can be overridden when the caller is
         # not necessarily a setup script run from the command-line.
         self.script_name = None
-        self.script_args = None
+        self.script_args: list[str] | None = None
 
         # 'command_options' is where we store command options between
         # parsing them (from config files, the command-line, etc.) and when
@@ -269,6 +278,8 @@ def __init__(self, attrs=None):  # noqa: C901
         self.want_user_cfg = True
 
         if self.script_args is not None:
+            # Coerce any possible iterable from attrs into a list
+            self.script_args = list(self.script_args)
             for arg in self.script_args:
                 if not arg.startswith('-'):
                     break
@@ -722,7 +733,7 @@ def print_command_list(self, commands, header, max_length):
             except AttributeError:
                 description = "(no description available)"
 
-            print("  %-*s  %s" % (max_length, cmd, description))
+            print(f"  {cmd:<{max_length}}  {description}")
 
     def print_commands(self):
         """Print out a help message listing all available commands with a
@@ -829,7 +840,15 @@ def get_command_class(self, command):
 
         raise DistutilsModuleError(f"invalid command '{command}'")
 
-    def get_command_obj(self, command, create=True):
+    @overload
+    def get_command_obj(
+        self, command: str, create: Literal[True] = True
+    ) -> Command: ...
+    @overload
+    def get_command_obj(
+        self, command: str, create: Literal[False]
+    ) -> Command | None: ...
+    def get_command_obj(self, command: str, create: bool = True) -> Command | None:
         """Return the command object for 'command'.  Normally this object
         is cached on a previous call to 'get_command_obj()'; if no command
         object for 'command' is in the cache, then we either create and
@@ -900,7 +919,17 @@ def _set_command_options(self, command_obj, option_dict=None):  # noqa: C901
             except ValueError as msg:
                 raise DistutilsOptionError(msg)
 
-    def reinitialize_command(self, command, reinit_subcommands=False):
+    @overload
+    def reinitialize_command(
+        self, command: str, reinit_subcommands: bool = False
+    ) -> Command: ...
+    @overload
+    def reinitialize_command(
+        self, command: _CommandT, reinit_subcommands: bool = False
+    ) -> _CommandT: ...
+    def reinitialize_command(
+        self, command: str | Command, reinit_subcommands=False
+    ) -> Command:
         """Reinitializes a command to the state it was in when first
         returned by 'get_command_obj()': ie., initialized but not yet
         finalized.  This provides the opportunity to sneak option
diff --git a/setuptools/_distutils/extension.py b/setuptools/_distutils/extension.py
index 33159079c1..e053273436 100644
--- a/setuptools/_distutils/extension.py
+++ b/setuptools/_distutils/extension.py
@@ -26,12 +26,14 @@ class Extension:
       name : string
         the full name of the extension, including any packages -- ie.
         *not* a filename or pathname, but Python dotted name
-      sources : [string | os.PathLike]
-        list of source filenames, relative to the distribution root
-        (where the setup script lives), in Unix form (slash-separated)
-        for portability.  Source files may be C, C++, SWIG (.i),
-        platform-specific resource files, or whatever else is recognized
-        by the "build_ext" command as source for a Python extension.
+      sources : Iterable[string | os.PathLike]
+        iterable of source filenames (except strings, which could be misinterpreted
+        as a single filename), relative to the distribution root (where the setup
+        script lives), in Unix form (slash-separated) for portability. Can be any
+        non-string iterable (list, tuple, set, etc.) containing strings or
+        PathLike objects. Source files may be C, C++, SWIG (.i), platform-specific
+        resource files, or whatever else is recognized by the "build_ext" command
+        as source for a Python extension.
       include_dirs : [string]
         list of directories to search for C/C++ header files (in Unix
         form for portability)
@@ -105,17 +107,23 @@ def __init__(
         **kw,  # To catch unknown keywords
     ):
         if not isinstance(name, str):
-            raise AssertionError("'name' must be a string")  # noqa: TRY004
-        if not (
-            isinstance(sources, list)
-            and all(isinstance(v, (str, os.PathLike)) for v in sources)
-        ):
-            raise AssertionError(
-                "'sources' must be a list of strings or PathLike objects."
+            raise TypeError("'name' must be a string")
+
+        # handle the string case first; since strings are iterable, disallow them
+        if isinstance(sources, str):
+            raise TypeError(
+                "'sources' must be an iterable of strings or PathLike objects, not a string"
+            )
+
+        # now we check if it's iterable and contains valid types
+        try:
+            self.sources = list(map(os.fspath, sources))
+        except TypeError:
+            raise TypeError(
+                "'sources' must be an iterable of strings or PathLike objects"
             )
 
         self.name = name
-        self.sources = list(map(os.fspath, sources))
         self.include_dirs = include_dirs or []
         self.define_macros = define_macros or []
         self.undef_macros = undef_macros or []
diff --git a/setuptools/_distutils/fancy_getopt.py b/setuptools/_distutils/fancy_getopt.py
index 907cc2b73c..1a1d3a05da 100644
--- a/setuptools/_distutils/fancy_getopt.py
+++ b/setuptools/_distutils/fancy_getopt.py
@@ -8,11 +8,14 @@
   * options set attributes of a passed-in object
 """
 
+from __future__ import annotations
+
 import getopt
 import re
 import string
 import sys
-from typing import Any, Sequence
+from collections.abc import Sequence
+from typing import Any
 
 from .errors import DistutilsArgError, DistutilsGetoptError
 
@@ -167,8 +170,7 @@ def _grok_option_table(self):  # noqa: C901
 
             if not ((short is None) or (isinstance(short, str) and len(short) == 1)):
                 raise DistutilsGetoptError(
-                    f"invalid short option '{short}': "
-                    "must a single character or None"
+                    f"invalid short option '{short}': must a single character or None"
                 )
 
             self.repeat[long] = repeat
@@ -219,7 +221,7 @@ def _grok_option_table(self):  # noqa: C901
                 self.short_opts.append(short)
                 self.short2long[short[0]] = long
 
-    def getopt(self, args=None, object=None):  # noqa: C901
+    def getopt(self, args: Sequence[str] | None = None, object=None):  # noqa: C901
         """Parse command-line options in args. Store as attributes on object.
 
         If 'args' is None or not supplied, uses 'sys.argv[1:]'.  If
@@ -351,18 +353,18 @@ def generate_help(self, header=None):  # noqa: C901
             # Case 1: no short option at all (makes life easy)
             if short is None:
                 if text:
-                    lines.append("  --%-*s  %s" % (max_opt, long, text[0]))
+                    lines.append(f"  --{long:<{max_opt}}  {text[0]}")
                 else:
-                    lines.append("  --%-*s  " % (max_opt, long))
+                    lines.append(f"  --{long:<{max_opt}}")
 
             # Case 2: we have a short option, so we have to include it
             # just after the long option
             else:
                 opt_names = f"{long} (-{short})"
                 if text:
-                    lines.append("  --%-*s  %s" % (max_opt, opt_names, text[0]))
+                    lines.append(f"  --{opt_names:<{max_opt}}  {text[0]}")
                 else:
-                    lines.append("  --%-*s" % opt_names)
+                    lines.append(f"  --{opt_names:<{max_opt}}")
 
             for ell in text[1:]:
                 lines.append(big_indent + ell)
@@ -375,7 +377,7 @@ def print_help(self, header=None, file=None):
             file.write(line + "\n")
 
 
-def fancy_getopt(options, negative_opt, object, args):
+def fancy_getopt(options, negative_opt, object, args: Sequence[str] | None):
     parser = FancyGetopt(options)
     parser.set_negative_aliases(negative_opt)
     return parser.getopt(args, object)
@@ -464,6 +466,6 @@ def __init__(self, options: Sequence[Any] = []):
 say, "How should I know?"].)"""
 
     for w in (10, 20, 30, 40):
-        print("width: %d" % w)
+        print(f"width: {w}")
         print("\n".join(wrap_text(text, w)))
         print()
diff --git a/setuptools/_distutils/file_util.py b/setuptools/_distutils/file_util.py
index 85ee4dafcb..0acc8cb84b 100644
--- a/setuptools/_distutils/file_util.py
+++ b/setuptools/_distutils/file_util.py
@@ -118,7 +118,7 @@ def copy_file(  # noqa: C901
     if update and not newer(src, dst):
         if verbose >= 1:
             log.debug("not copying %s (output up-to-date)", src)
-        return (dst, 0)
+        return (dst, False)
 
     try:
         action = _copy_action[link]
@@ -132,7 +132,7 @@ def copy_file(  # noqa: C901
             log.info("%s %s -> %s", action, src, dst)
 
     if dry_run:
-        return (dst, 1)
+        return (dst, True)
 
     # If linking (hard or symbolic), use the appropriate system call
     # (Unix only, of course, but that's the caller's responsibility)
@@ -146,11 +146,11 @@ def copy_file(  # noqa: C901
                 #  even under Unix, see issue #8876).
                 pass
             else:
-                return (dst, 1)
+                return (dst, True)
     elif link == 'sym':
         if not (os.path.exists(dst) and os.path.samefile(src, dst)):
             os.symlink(src, dst)
-            return (dst, 1)
+            return (dst, True)
 
     # Otherwise (non-Mac, not linking), copy the file contents and
     # (optionally) copy the times and mode.
@@ -165,7 +165,7 @@ def copy_file(  # noqa: C901
         if preserve_mode:
             os.chmod(dst, S_IMODE(st[ST_MODE]))
 
-    return (dst, 1)
+    return (dst, True)
 
 
 # XXX I suspect this is Unix-specific -- need porting help!
diff --git a/setuptools/_distutils/filelist.py b/setuptools/_distutils/filelist.py
index 44ae9e67ef..9857b19549 100644
--- a/setuptools/_distutils/filelist.py
+++ b/setuptools/_distutils/filelist.py
@@ -127,10 +127,7 @@ def process_template_line(self, line):  # noqa: C901
             for pattern in patterns:
                 if not self.exclude_pattern(pattern, anchor=True):
                     log.warning(
-                        (
-                            "warning: no previously-included files "
-                            "found matching '%s'"
-                        ),
+                        "warning: no previously-included files found matching '%s'",
                         pattern,
                     )
 
diff --git a/setuptools/_distutils/spawn.py b/setuptools/_distutils/spawn.py
index 107b011397..ba280334d1 100644
--- a/setuptools/_distutils/spawn.py
+++ b/setuptools/_distutils/spawn.py
@@ -12,7 +12,7 @@
 import subprocess
 import sys
 import warnings
-from typing import Mapping
+from collections.abc import Mapping
 
 from ._log import log
 from .debug import DEBUG
diff --git a/setuptools/_distutils/sysconfig.py b/setuptools/_distutils/sysconfig.py
index da1eecbe7e..358d1079dc 100644
--- a/setuptools/_distutils/sysconfig.py
+++ b/setuptools/_distutils/sysconfig.py
@@ -107,7 +107,7 @@ def get_python_version():
     leaving off the patchlevel.  Sample return values could be '1.5'
     or '2.2'.
     """
-    return '%d.%d' % sys.version_info[:2]
+    return f'{sys.version_info.major}.{sys.version_info.minor}'
 
 
 def get_python_inc(plat_specific=False, prefix=None):
@@ -340,6 +340,7 @@ def customize_compiler(compiler):
 
         ldshared = _add_flags(ldshared, 'LD')
         ldcxxshared = _add_flags(ldcxxshared, 'LD')
+        cflags = os.environ.get('CFLAGS', cflags)
         cflags = _add_flags(cflags, 'C')
         ldshared = _add_flags(ldshared, 'C')
         cxxflags = os.environ.get('CXXFLAGS', cxxflags)
diff --git a/setuptools/_distutils/tests/__init__.py b/setuptools/_distutils/tests/__init__.py
index 93fbf49074..5a8ab06100 100644
--- a/setuptools/_distutils/tests/__init__.py
+++ b/setuptools/_distutils/tests/__init__.py
@@ -8,7 +8,7 @@
 """
 
 import shutil
-from typing import Sequence
+from collections.abc import Sequence
 
 
 def missing_compiler_executable(cmd_names: Sequence[str] = []):  # pragma: no cover
diff --git a/setuptools/_distutils/tests/compat/py38.py b/setuptools/_distutils/tests/compat/py38.py
deleted file mode 100644
index 211d3a6c50..0000000000
--- a/setuptools/_distutils/tests/compat/py38.py
+++ /dev/null
@@ -1,50 +0,0 @@
-# flake8: noqa
-
-import contextlib
-import builtins
-import sys
-
-from test.support import requires_zlib
-import test.support
-
-
-ModuleNotFoundError = getattr(builtins, 'ModuleNotFoundError', ImportError)
-
-try:
-    from test.support.warnings_helper import check_warnings
-except (ModuleNotFoundError, ImportError):
-    from test.support import check_warnings
-
-
-try:
-    from test.support.os_helper import (
-        rmtree,
-        EnvironmentVarGuard,
-        unlink,
-        skip_unless_symlink,
-        temp_dir,
-    )
-except (ModuleNotFoundError, ImportError):
-    from test.support import (
-        rmtree,
-        EnvironmentVarGuard,
-        unlink,
-        skip_unless_symlink,
-        temp_dir,
-    )
-
-
-try:
-    from test.support.import_helper import (
-        DirsOnSysPath,
-        CleanImport,
-    )
-except (ModuleNotFoundError, ImportError):
-    from test.support import (
-        DirsOnSysPath,
-        CleanImport,
-    )
-
-
-if sys.version_info < (3, 9):
-    requires_zlib = lambda: test.support.requires_zlib
diff --git a/setuptools/_distutils/tests/compat/py39.py b/setuptools/_distutils/tests/compat/py39.py
new file mode 100644
index 0000000000..aca3939a0c
--- /dev/null
+++ b/setuptools/_distutils/tests/compat/py39.py
@@ -0,0 +1,40 @@
+import sys
+
+if sys.version_info >= (3, 10):
+    from test.support.import_helper import (
+        CleanImport as CleanImport,
+    )
+    from test.support.import_helper import (
+        DirsOnSysPath as DirsOnSysPath,
+    )
+    from test.support.os_helper import (
+        EnvironmentVarGuard as EnvironmentVarGuard,
+    )
+    from test.support.os_helper import (
+        rmtree as rmtree,
+    )
+    from test.support.os_helper import (
+        skip_unless_symlink as skip_unless_symlink,
+    )
+    from test.support.os_helper import (
+        unlink as unlink,
+    )
+else:
+    from test.support import (
+        CleanImport as CleanImport,
+    )
+    from test.support import (
+        DirsOnSysPath as DirsOnSysPath,
+    )
+    from test.support import (
+        EnvironmentVarGuard as EnvironmentVarGuard,
+    )
+    from test.support import (
+        rmtree as rmtree,
+    )
+    from test.support import (
+        skip_unless_symlink as skip_unless_symlink,
+    )
+    from test.support import (
+        unlink as unlink,
+    )
diff --git a/setuptools/_distutils/tests/test_bdist_rpm.py b/setuptools/_distutils/tests/test_bdist_rpm.py
index 1109fdf117..75051430e2 100644
--- a/setuptools/_distutils/tests/test_bdist_rpm.py
+++ b/setuptools/_distutils/tests/test_bdist_rpm.py
@@ -8,8 +8,7 @@
 from distutils.tests import support
 
 import pytest
-
-from .compat.py38 import requires_zlib
+from test.support import requires_zlib
 
 SETUP_PY = """\
 from distutils.core import setup
diff --git a/setuptools/_distutils/tests/test_build.py b/setuptools/_distutils/tests/test_build.py
index d379aca0bb..f7fe69acd1 100644
--- a/setuptools/_distutils/tests/test_build.py
+++ b/setuptools/_distutils/tests/test_build.py
@@ -40,7 +40,9 @@ def test_finalize_options(self):
         assert cmd.build_temp == wanted
 
         # build_scripts is build/scripts-x.x
-        wanted = os.path.join(cmd.build_base, 'scripts-%d.%d' % sys.version_info[:2])
+        wanted = os.path.join(
+            cmd.build_base, f'scripts-{sys.version_info.major}.{sys.version_info.minor}'
+        )
         assert cmd.build_scripts == wanted
 
         # executable is os.path.normpath(sys.executable)
diff --git a/setuptools/_distutils/tests/test_build_ext.py b/setuptools/_distutils/tests/test_build_ext.py
index 8bd3cef855..beeba4850c 100644
--- a/setuptools/_distutils/tests/test_build_ext.py
+++ b/setuptools/_distutils/tests/test_build_ext.py
@@ -19,11 +19,7 @@
 )
 from distutils.extension import Extension
 from distutils.tests import missing_compiler_executable
-from distutils.tests.support import (
-    TempdirManager,
-    copy_xxmodule_c,
-    fixup_build_ext,
-)
+from distutils.tests.support import TempdirManager, copy_xxmodule_c, fixup_build_ext
 from io import StringIO
 
 import jaraco.path
@@ -31,7 +27,7 @@
 import pytest
 from test import support
 
-from .compat import py38 as import_helper
+from .compat import py39 as import_helper
 
 
 @pytest.fixture()
@@ -522,14 +518,15 @@ def _try_compile_deployment_target(self, operator, target):  # pragma: no cover
         # at least one value we test with will not exist yet.
         if target[:2] < (10, 10):
             # for 10.1 through 10.9.x -> "10n0"
-            target = '%02d%01d0' % target
+            tmpl = '{:02}{:01}0'
         else:
             # for 10.10 and beyond -> "10nn00"
             if len(target) >= 2:
-                target = '%02d%02d00' % target
+                tmpl = '{:02}{:02}00'
             else:
                 # 11 and later can have no minor version (11 instead of 11.0)
-                target = '%02d0000' % target
+                tmpl = '{:02}0000'
+        target = tmpl.format(*target)
         deptarget_ext = Extension(
             'deptarget',
             [self.tmp_path / 'deptargetmodule.c'],
diff --git a/setuptools/_distutils/tests/test_dir_util.py b/setuptools/_distutils/tests/test_dir_util.py
index fcc37ac568..326cb34614 100644
--- a/setuptools/_distutils/tests/test_dir_util.py
+++ b/setuptools/_distutils/tests/test_dir_util.py
@@ -3,6 +3,7 @@
 import os
 import pathlib
 import stat
+import sys
 import unittest.mock as mock
 from distutils import dir_util, errors
 from distutils.dir_util import (
@@ -106,8 +107,9 @@ def test_copy_tree_exception_in_listdir(self):
         """
         An exception in listdir should raise a DistutilsFileError
         """
-        with mock.patch("os.listdir", side_effect=OSError()), pytest.raises(
-            errors.DistutilsFileError
+        with (
+            mock.patch("os.listdir", side_effect=OSError()),
+            pytest.raises(errors.DistutilsFileError),
         ):
             src = self.tempdirs[-1]
             dir_util.copy_tree(src, None)
@@ -123,6 +125,9 @@ class FailPath(pathlib.Path):
             def mkdir(self, *args, **kwargs):
                 raise OSError("Failed to create directory")
 
+            if sys.version_info < (3, 12):
+                _flavour = pathlib.Path()._flavour
+
         target = tmp_path / 'foodir'
 
         with pytest.raises(errors.DistutilsFileError):
diff --git a/setuptools/_distutils/tests/test_dist.py b/setuptools/_distutils/tests/test_dist.py
index 4d78a19803..2c5beebe64 100644
--- a/setuptools/_distutils/tests/test_dist.py
+++ b/setuptools/_distutils/tests/test_dist.py
@@ -13,6 +13,7 @@
 from distutils.cmd import Command
 from distutils.dist import Distribution, fix_help_options
 from distutils.tests import support
+from typing import ClassVar
 
 import jaraco.path
 import pytest
@@ -23,7 +24,7 @@
 class test_dist(Command):
     """Sample distutils extension command."""
 
-    user_options = [
+    user_options: ClassVar[list[tuple[str, str, str]]] = [
         ("sample-option=", "S", "help text"),
     ]
 
@@ -246,6 +247,12 @@ def test_find_config_files_disable(self, temp_home):
         # make sure --no-user-cfg disables the user cfg file
         assert len(all_files) - 1 == len(files)
 
+    def test_script_args_list_coercion(self):
+        d = Distribution(attrs={'script_args': ('build', '--no-user-cfg')})
+
+        # make sure script_args is a list even if it started as a different iterable
+        assert d.script_args == ['build', '--no-user-cfg']
+
     @pytest.mark.skipif(
         'platform.system() == "Windows"',
         reason='Windows does not honor chmod 000',
diff --git a/setuptools/_distutils/tests/test_extension.py b/setuptools/_distutils/tests/test_extension.py
index 41872e04e8..5e8e768223 100644
--- a/setuptools/_distutils/tests/test_extension.py
+++ b/setuptools/_distutils/tests/test_extension.py
@@ -6,8 +6,7 @@
 from distutils.extension import Extension, read_setup_file
 
 import pytest
-
-from .compat.py38 import check_warnings
+from test.support.warnings_helper import check_warnings
 
 
 class TestExtension:
@@ -63,22 +62,32 @@ def test_read_setup_file(self):
 
     def test_extension_init(self):
         # the first argument, which is the name, must be a string
-        with pytest.raises(AssertionError):
+        with pytest.raises(TypeError):
             Extension(1, [])
         ext = Extension('name', [])
         assert ext.name == 'name'
 
         # the second argument, which is the list of files, must
-        # be a list of strings or PathLike objects
-        with pytest.raises(AssertionError):
+        # be an iterable of strings or PathLike objects, and not a string
+        with pytest.raises(TypeError):
             Extension('name', 'file')
-        with pytest.raises(AssertionError):
+        with pytest.raises(TypeError):
             Extension('name', ['file', 1])
         ext = Extension('name', ['file1', 'file2'])
         assert ext.sources == ['file1', 'file2']
         ext = Extension('name', [pathlib.Path('file1'), pathlib.Path('file2')])
         assert ext.sources == ['file1', 'file2']
 
+        # any non-string iterable of strings or PathLike objects should work
+        ext = Extension('name', ('file1', 'file2'))  # tuple
+        assert ext.sources == ['file1', 'file2']
+        ext = Extension('name', {'file1', 'file2'})  # set
+        assert sorted(ext.sources) == ['file1', 'file2']
+        ext = Extension('name', iter(['file1', 'file2']))  # iterator
+        assert ext.sources == ['file1', 'file2']
+        ext = Extension('name', [pathlib.Path('file1'), 'file2'])  # mixed types
+        assert ext.sources == ['file1', 'file2']
+
         # others arguments have defaults
         for attr in (
             'include_dirs',
diff --git a/setuptools/_distutils/tests/test_file_util.py b/setuptools/_distutils/tests/test_file_util.py
index 85ac2136b3..a75d4a0317 100644
--- a/setuptools/_distutils/tests/test_file_util.py
+++ b/setuptools/_distutils/tests/test_file_util.py
@@ -44,18 +44,19 @@ def test_move_file_verbosity(self, caplog):
 
     def test_move_file_exception_unpacking_rename(self):
         # see issue 22182
-        with mock.patch("os.rename", side_effect=OSError("wrong", 1)), pytest.raises(
-            DistutilsFileError
+        with (
+            mock.patch("os.rename", side_effect=OSError("wrong", 1)),
+            pytest.raises(DistutilsFileError),
         ):
             jaraco.path.build({self.source: 'spam eggs'})
             move_file(self.source, self.target, verbose=False)
 
     def test_move_file_exception_unpacking_unlink(self):
         # see issue 22182
-        with mock.patch(
-            "os.rename", side_effect=OSError(errno.EXDEV, "wrong")
-        ), mock.patch("os.unlink", side_effect=OSError("wrong", 1)), pytest.raises(
-            DistutilsFileError
+        with (
+            mock.patch("os.rename", side_effect=OSError(errno.EXDEV, "wrong")),
+            mock.patch("os.unlink", side_effect=OSError("wrong", 1)),
+            pytest.raises(DistutilsFileError),
         ):
             jaraco.path.build({self.source: 'spam eggs'})
             move_file(self.source, self.target, verbose=False)
diff --git a/setuptools/_distutils/tests/test_filelist.py b/setuptools/_distutils/tests/test_filelist.py
index ec7e5cf363..130e6fb53b 100644
--- a/setuptools/_distutils/tests/test_filelist.py
+++ b/setuptools/_distutils/tests/test_filelist.py
@@ -10,7 +10,7 @@
 import jaraco.path
 import pytest
 
-from .compat import py38 as os_helper
+from .compat import py39 as os_helper
 
 MANIFEST_IN = """\
 include ok
diff --git a/setuptools/_distutils/tests/test_spawn.py b/setuptools/_distutils/tests/test_spawn.py
index fd7b669cbf..3b9fc926f6 100644
--- a/setuptools/_distutils/tests/test_spawn.py
+++ b/setuptools/_distutils/tests/test_spawn.py
@@ -12,7 +12,7 @@
 import pytest
 from test.support import unix_shell
 
-from .compat import py38 as os_helper
+from .compat import py39 as os_helper
 
 
 class TestSpawn(support.TempdirManager):
@@ -73,9 +73,12 @@ def test_find_executable(self, tmp_path):
         # PATH='': no match, except in the current directory
         with os_helper.EnvironmentVarGuard() as env:
             env['PATH'] = ''
-            with mock.patch(
-                'distutils.spawn.os.confstr', return_value=tmp_dir, create=True
-            ), mock.patch('distutils.spawn.os.defpath', tmp_dir):
+            with (
+                mock.patch(
+                    'distutils.spawn.os.confstr', return_value=tmp_dir, create=True
+                ),
+                mock.patch('distutils.spawn.os.defpath', tmp_dir),
+            ):
                 rv = find_executable(program)
                 assert rv is None
 
@@ -87,9 +90,10 @@ def test_find_executable(self, tmp_path):
         # PATH=':': explicitly looks in the current directory
         with os_helper.EnvironmentVarGuard() as env:
             env['PATH'] = os.pathsep
-            with mock.patch(
-                'distutils.spawn.os.confstr', return_value='', create=True
-            ), mock.patch('distutils.spawn.os.defpath', ''):
+            with (
+                mock.patch('distutils.spawn.os.confstr', return_value='', create=True),
+                mock.patch('distutils.spawn.os.defpath', ''),
+            ):
                 rv = find_executable(program)
                 assert rv is None
 
@@ -103,16 +107,22 @@ def test_find_executable(self, tmp_path):
             env.pop('PATH', None)
 
             # without confstr
-            with mock.patch(
-                'distutils.spawn.os.confstr', side_effect=ValueError, create=True
-            ), mock.patch('distutils.spawn.os.defpath', tmp_dir):
+            with (
+                mock.patch(
+                    'distutils.spawn.os.confstr', side_effect=ValueError, create=True
+                ),
+                mock.patch('distutils.spawn.os.defpath', tmp_dir),
+            ):
                 rv = find_executable(program)
                 assert rv == filename
 
             # with confstr
-            with mock.patch(
-                'distutils.spawn.os.confstr', return_value=tmp_dir, create=True
-            ), mock.patch('distutils.spawn.os.defpath', ''):
+            with (
+                mock.patch(
+                    'distutils.spawn.os.confstr', return_value=tmp_dir, create=True
+                ),
+                mock.patch('distutils.spawn.os.defpath', ''),
+            ):
                 rv = find_executable(program)
                 assert rv == filename
 
diff --git a/setuptools/_distutils/tests/test_sysconfig.py b/setuptools/_distutils/tests/test_sysconfig.py
index 49274a36ae..867e7dcb39 100644
--- a/setuptools/_distutils/tests/test_sysconfig.py
+++ b/setuptools/_distutils/tests/test_sysconfig.py
@@ -130,9 +130,11 @@ def test_customize_compiler(self):
         comp = self.customize_compiler()
         assert comp.exes['archiver'] == 'env_ar --env-arflags'
         assert comp.exes['preprocessor'] == 'env_cpp --env-cppflags'
-        assert comp.exes['compiler'] == 'env_cc --sc-cflags --env-cflags --env-cppflags'
+        assert (
+            comp.exes['compiler'] == 'env_cc --env-cflags --env-cflags --env-cppflags'
+        )
         assert comp.exes['compiler_so'] == (
-            'env_cc --sc-cflags --env-cflags --env-cppflags --sc-ccshared'
+            'env_cc --env-cflags --env-cflags --env-cppflags --sc-ccshared'
         )
         assert (
             comp.exes['compiler_cxx']
diff --git a/setuptools/_distutils/tests/test_unixccompiler.py b/setuptools/_distutils/tests/test_unixccompiler.py
index 50b66544a8..2c2f4aaec2 100644
--- a/setuptools/_distutils/tests/test_unixccompiler.py
+++ b/setuptools/_distutils/tests/test_unixccompiler.py
@@ -12,7 +12,7 @@
 import pytest
 
 from . import support
-from .compat.py38 import EnvironmentVarGuard
+from .compat.py39 import EnvironmentVarGuard
 
 
 @pytest.fixture(autouse=True)
@@ -272,13 +272,12 @@ def gcvs(*args, _orig=sysconfig.get_config_vars):
 
         sysconfig.get_config_var = gcv
         sysconfig.get_config_vars = gcvs
-        with mock.patch.object(
-            self.cc, 'spawn', return_value=None
-        ) as mock_spawn, mock.patch.object(
-            self.cc, '_need_link', return_value=True
-        ), mock.patch.object(
-            self.cc, 'mkpath', return_value=None
-        ), EnvironmentVarGuard() as env:
+        with (
+            mock.patch.object(self.cc, 'spawn', return_value=None) as mock_spawn,
+            mock.patch.object(self.cc, '_need_link', return_value=True),
+            mock.patch.object(self.cc, 'mkpath', return_value=None),
+            EnvironmentVarGuard() as env,
+        ):
             env['CC'] = 'ccache my_cc'
             env['CXX'] = 'my_cxx'
             del env['LDSHARED']
diff --git a/setuptools/_distutils/tests/test_version.py b/setuptools/_distutils/tests/test_version.py
index 1508e1cc0a..b68f097724 100644
--- a/setuptools/_distutils/tests/test_version.py
+++ b/setuptools/_distutils/tests/test_version.py
@@ -53,9 +53,9 @@ def test_cmp_strict(self):
             res = StrictVersion(v1)._cmp(v2)
             assert res == wanted, f'cmp({v1}, {v2}) should be {wanted}, got {res}'
             res = StrictVersion(v1)._cmp(object())
-            assert (
-                res is NotImplemented
-            ), f'cmp({v1}, {v2}) should be NotImplemented, got {res}'
+            assert res is NotImplemented, (
+                f'cmp({v1}, {v2}) should be NotImplemented, got {res}'
+            )
 
     def test_cmp(self):
         versions = (
@@ -75,6 +75,6 @@ def test_cmp(self):
             res = LooseVersion(v1)._cmp(v2)
             assert res == wanted, f'cmp({v1}, {v2}) should be {wanted}, got {res}'
             res = LooseVersion(v1)._cmp(object())
-            assert (
-                res is NotImplemented
-            ), f'cmp({v1}, {v2}) should be NotImplemented, got {res}'
+            assert res is NotImplemented, (
+                f'cmp({v1}, {v2}) should be NotImplemented, got {res}'
+            )
diff --git a/setuptools/_distutils/text_file.py b/setuptools/_distutils/text_file.py
index fec29c73b0..89d9048d59 100644
--- a/setuptools/_distutils/text_file.py
+++ b/setuptools/_distutils/text_file.py
@@ -133,9 +133,9 @@ def gen_error(self, msg, line=None):
             line = self.current_line
         outmsg.append(self.filename + ", ")
         if isinstance(line, (list, tuple)):
-            outmsg.append("lines %d-%d: " % tuple(line))
+            outmsg.append("lines {}-{}: ".format(*line))
         else:
-            outmsg.append("line %d: " % line)
+            outmsg.append(f"line {int(line)}: ")
         outmsg.append(str(msg))
         return "".join(outmsg)
 
diff --git a/setuptools/_distutils/util.py b/setuptools/_distutils/util.py
index 609c1a50cd..83ad39e958 100644
--- a/setuptools/_distutils/util.py
+++ b/setuptools/_distutils/util.py
@@ -25,7 +25,7 @@
 from .spawn import spawn
 
 
-def get_host_platform():
+def get_host_platform() -> str:
     """
     Return a string that identifies the current platform. Use this
     function to distinguish platform-specific build directories and
@@ -34,15 +34,7 @@ def get_host_platform():
 
     # This function initially exposed platforms as defined in Python 3.9
     # even with older Python versions when distutils was split out.
-    # Now it delegates to stdlib sysconfig, but maintains compatibility.
-
-    if sys.version_info < (3, 9):
-        if os.name == "posix" and hasattr(os, 'uname'):
-            osname, host, release, version, machine = os.uname()
-            if osname[:3] == "aix":
-                from .compat.py38 import aix_platform
-
-                return aix_platform(osname, version, release)
+    # Now it delegates to stdlib sysconfig.
 
     return sysconfig.get_platform()
 
@@ -288,7 +280,7 @@ def split_quoted(s):
             elif s[end] == '"':  # slurp doubly-quoted string
                 m = _dquote_re.match(s, end)
             else:
-                raise RuntimeError("this can't happen (bad char '%c')" % s[end])
+                raise RuntimeError(f"this can't happen (bad char '{s[end]}')")
 
             if m is None:
                 raise ValueError(f"bad string (mismatched {s[end]} quotes?)")
@@ -503,3 +495,8 @@ def is_mingw():
     get_platform() starts with 'mingw'.
     """
     return sys.platform == 'win32' and get_platform().startswith('mingw')
+
+
+def is_freethreaded():
+    """Return True if the Python interpreter is built with free threading support."""
+    return bool(sysconfig.get_config_var('Py_GIL_DISABLED'))
diff --git a/setuptools/_distutils/version.py b/setuptools/_distutils/version.py
index 942b56bf94..2223ee9c8c 100644
--- a/setuptools/_distutils/version.py
+++ b/setuptools/_distutils/version.py
@@ -53,8 +53,7 @@ def __init__(self, vstring=None):
         if vstring:
             self.parse(vstring)
         warnings.warn(
-            "distutils Version classes are deprecated. "
-            "Use packaging.version instead.",
+            "distutils Version classes are deprecated. Use packaging.version instead.",
             DeprecationWarning,
             stacklevel=2,
         )