Merge branch 'main' into debt/remove-easy-installdebt/remove-easy-install

64 files changed, 794 insertions, 779 deletions

diff --git a/setuptools/_distutils/_collections.py b/setuptools/_distutils/_collections.py
new file mode 100644
index 00000000..98fce800
--- /dev/null
+++ b/setuptools/_distutils/_collections.py
@@ -0,0 +1,56 @@
+import collections
+import itertools
+
+
+# from jaraco.collections 3.5.1
+class DictStack(list, collections.abc.Mapping):
+    """
+    A stack of dictionaries that behaves as a view on those dictionaries,
+    giving preference to the last.
+
+    >>> stack = DictStack([dict(a=1, c=2), dict(b=2, a=2)])
+    >>> stack['a']
+    2
+    >>> stack['b']
+    2
+    >>> stack['c']
+    2
+    >>> len(stack)
+    3
+    >>> stack.push(dict(a=3))
+    >>> stack['a']
+    3
+    >>> set(stack.keys()) == set(['a', 'b', 'c'])
+    True
+    >>> set(stack.items()) == set([('a', 3), ('b', 2), ('c', 2)])
+    True
+    >>> dict(**stack) == dict(stack) == dict(a=3, c=2, b=2)
+    True
+    >>> d = stack.pop()
+    >>> stack['a']
+    2
+    >>> d = stack.pop()
+    >>> stack['a']
+    1
+    >>> stack.get('b', None)
+    >>> 'c' in stack
+    True
+    """
+
+    def __iter__(self):
+        dicts = list.__iter__(self)
+        return iter(set(itertools.chain.from_iterable(c.keys() for c in dicts)))
+
+    def __getitem__(self, key):
+        for scope in reversed(tuple(list.__iter__(self))):
+            if key in scope:
+                return scope[key]
+        raise KeyError(key)
+
+    push = list.append
+
+    def __contains__(self, other):
+        return collections.abc.Mapping.__contains__(self, other)
+
+    def __len__(self):
+        return len(list(iter(self)))
diff --git a/setuptools/_distutils/_macos_compat.py b/setuptools/_distutils/_macos_compat.py
new file mode 100644
index 00000000..17769e91
--- /dev/null
+++ b/setuptools/_distutils/_macos_compat.py
@@ -0,0 +1,12 @@
+import sys
+import importlib
+
+
+def bypass_compiler_fixup(cmd, args):
+    return cmd
+
+
+if sys.platform == 'darwin':
+    compiler_fixup = importlib.import_module('_osx_support').compiler_fixup
+else:
+    compiler_fixup = bypass_compiler_fixup
diff --git a/setuptools/_distutils/_msvccompiler.py b/setuptools/_distutils/_msvccompiler.py
index b7a06082..f2f801c5 100644
--- a/setuptools/_distutils/_msvccompiler.py
+++ b/setuptools/_distutils/_msvccompiler.py
@@ -203,7 +203,7 @@ class MSVCCompiler(CCompiler) :
 
 
     def __init__(self, verbose=0, dry_run=0, force=0):
-        CCompiler.__init__ (self, verbose, dry_run, force)
+        super().__init__(verbose, dry_run, force)
         # target platform (.plat_name is consistent with 'bdist')
         self.plat_name = None
         self.initialized = False
@@ -527,7 +527,7 @@ class MSVCCompiler(CCompiler) :
             return
         warnings.warn(
             "Fallback spawn triggered. Please update distutils monkeypatch.")
-        with unittest.mock.patch('os.environ', env):
+        with unittest.mock.patch.dict('os.environ', env):
             bag.value = super().spawn(cmd)
 
     # -- Miscellaneous methods -----------------------------------------
diff --git a/setuptools/_distutils/bcppcompiler.py b/setuptools/_distutils/bcppcompiler.py
index 071fea5d..2eb6d2e9 100644
--- a/setuptools/_distutils/bcppcompiler.py
+++ b/setuptools/_distutils/bcppcompiler.py
@@ -55,7 +55,7 @@ class BCPPCompiler(CCompiler) :
                   dry_run=0,
                   force=0):
 
-        CCompiler.__init__ (self, verbose, dry_run, force)
+        super().__init__(verbose, dry_run, force)
 
         # These executables are assumed to all be in the path.
         # Borland doesn't seem to use any special registry settings to
diff --git a/setuptools/_distutils/command/bdist_msi.py b/setuptools/_distutils/command/bdist_msi.py
index 0863a188..15259532 100644
--- a/setuptools/_distutils/command/bdist_msi.py
+++ b/setuptools/_distutils/command/bdist_msi.py
@@ -27,7 +27,7 @@ class PyDialog(Dialog):
     def __init__(self, *args, **kw):
         """Dialog(database, name, x, y, w, h, attributes, title, first,
         default, cancel, bitmap=true)"""
-        Dialog.__init__(self, *args)
+        super().__init__(*args)
         ruler = self.h - 36
         bmwidth = 152*ruler/328
         #if kw.get("bitmap", True):
diff --git a/setuptools/_distutils/command/build.py b/setuptools/_distutils/command/build.py
index 4355a632..9606b81a 100644
--- a/setuptools/_distutils/command/build.py
+++ b/setuptools/_distutils/command/build.py
@@ -81,7 +81,8 @@ class build(Command):
                             "--plat-name only supported on Windows (try "
                             "using './configure --help' on your platform)")
 
-        plat_specifier = ".%s-%d.%d" % (self.plat_name, *sys.version_info[:2])
+        plat_specifier = ".%s-%s" % (self.plat_name,
+                                     sys.implementation.cache_tag)
 
         # Make it so Python 2.x and Python 2.x with --with-pydebug don't
         # share the same build directories. Doing so confuses the build
diff --git a/setuptools/_distutils/command/build_ext.py b/setuptools/_distutils/command/build_ext.py
index 22628baf..181671bf 100644
--- a/setuptools/_distutils/command/build_ext.py
+++ b/setuptools/_distutils/command/build_ext.py
@@ -202,9 +202,7 @@ class build_ext(Command):
             # Append the source distribution include and library directories,
             # this allows distutils on windows to work in the source tree
             self.include_dirs.append(os.path.dirname(get_config_h_filename()))
-            _sys_home = getattr(sys, '_home', None)
-            if _sys_home:
-                self.library_dirs.append(_sys_home)
+            self.library_dirs.append(sys.base_exec_prefix)
 
             # Use the .lib files for the correct architecture
             if self.plat_name == 'win32':
diff --git a/setuptools/_distutils/command/build_scripts.py b/setuptools/_distutils/command/build_scripts.py
index e3312cf0..e56511da 100644
--- a/setuptools/_distutils/command/build_scripts.py
+++ b/setuptools/_distutils/command/build_scripts.py
@@ -2,7 +2,8 @@
 
 Implements the Distutils 'build_scripts' command."""
 
-import os, re
+import os
+import re
 from stat import ST_MODE
 from distutils import sysconfig
 from distutils.core import Command
@@ -11,8 +12,14 @@ from distutils.util import convert_path
 from distutils import log
 import tokenize
 
-# check if Python is called on the first line with this expression
-first_line_re = re.compile(b'^#!.*python[0-9.]*([ \t].*)?$')
+shebang_pattern = re.compile('^#!.*python[0-9.]*([ \t].*)?$')
+"""
+Pattern matching a Python interpreter indicated in first line of a script.
+"""
+
+# for Setuptools compatibility
+first_line_re = shebang_pattern
+
 
 class build_scripts(Command):
 
@@ -26,13 +33,11 @@ class build_scripts(Command):
 
     boolean_options = ['force']
 
-
     def initialize_options(self):
         self.build_dir = None
         self.scripts = None
         self.force = None
         self.executable = None
-        self.outfiles = None
 
     def finalize_options(self):
         self.set_undefined_options('build',
@@ -49,104 +54,117 @@ class build_scripts(Command):
             return
         self.copy_scripts()
 
-
     def copy_scripts(self):
-        r"""Copy each script listed in 'self.scripts'; if it's marked as a
-        Python script in the Unix way (first line matches 'first_line_re',
-        ie. starts with "\#!" and contains "python"), then adjust the first
-        line to refer to the current Python interpreter as we copy.
+        """
+        Copy each script listed in ``self.scripts``.
+
+        If a script is marked as a Python script (first line matches
+        'shebang_pattern', i.e. starts with ``#!`` and contains
+        "python"), then adjust in the copy the first line to refer to
+        the current Python interpreter.
         """
         self.mkpath(self.build_dir)
         outfiles = []
         updated_files = []
         for script in self.scripts:
-            adjust = False
-            script = convert_path(script)
-            outfile = os.path.join(self.build_dir, os.path.basename(script))
-            outfiles.append(outfile)
-
-            if not self.force and not newer(script, outfile):
-                log.debug("not copying %s (up-to-date)", script)
-                continue
-
-            # Always open the file, but ignore failures in dry-run mode --
-            # that way, we'll get accurate feedback if we can read the
-            # script.
-            try:
-                f = open(script, "rb")
-            except OSError:
-                if not self.dry_run:
-                    raise
-                f = None
-            else:
-                encoding, lines = tokenize.detect_encoding(f.readline)
-                f.seek(0)
-                first_line = f.readline()
-                if not first_line:
-                    self.warn("%s is an empty file (skipping)" % script)
-                    continue
-
-                match = first_line_re.match(first_line)
-                if match:
-                    adjust = True
-                    post_interp = match.group(1) or b''
-
-            if adjust:
-                log.info("copying and adjusting %s -> %s", script,
-                         self.build_dir)
-                updated_files.append(outfile)
-                if not self.dry_run:
-                    if not sysconfig.python_build:
-                        executable = self.executable
-                    else:
-                        executable = os.path.join(
-                            sysconfig.get_config_var("BINDIR"),
-                           "python%s%s" % (sysconfig.get_config_var("VERSION"),
-                                           sysconfig.get_config_var("EXE")))
-                    executable = os.fsencode(executable)
-                    shebang = b"#!" + executable + post_interp + b"\n"
-                    # Python parser starts to read a script using UTF-8 until
-                    # it gets a #coding:xxx cookie. The shebang has to be the
-                    # first line of a file, the #coding:xxx cookie cannot be
-                    # written before. So the shebang has to be decodable from
-                    # UTF-8.
-                    try:
-                        shebang.decode('utf-8')
-                    except UnicodeDecodeError:
-                        raise ValueError(
-                            "The shebang ({!r}) is not decodable "
-                            "from utf-8".format(shebang))
-                    # If the script is encoded to a custom encoding (use a
-                    # #coding:xxx cookie), the shebang has to be decodable from
-                    # the script encoding too.
-                    try:
-                        shebang.decode(encoding)
-                    except UnicodeDecodeError:
-                        raise ValueError(
-                            "The shebang ({!r}) is not decodable "
-                            "from the script encoding ({})"
-                            .format(shebang, encoding))
-                    with open(outfile, "wb") as outf:
-                        outf.write(shebang)
-                        outf.writelines(f.readlines())
-                if f:
-                    f.close()
-            else:
-                if f:
-                    f.close()
-                updated_files.append(outfile)
-                self.copy_file(script, outfile)
-
-        if os.name == 'posix':
-            for file in outfiles:
-                if self.dry_run:
-                    log.info("changing mode of %s", file)
-                else:
-                    oldmode = os.stat(file)[ST_MODE] & 0o7777
-                    newmode = (oldmode | 0o555) & 0o7777
-                    if newmode != oldmode:
-                        log.info("changing mode of %s from %o to %o",
-                                 file, oldmode, newmode)
-                        os.chmod(file, newmode)
-        # XXX should we modify self.outfiles?
+            self._copy_script(script, outfiles, updated_files)
+
+        self._change_modes(outfiles)
+
         return outfiles, updated_files
+
+    def _copy_script(self, script, outfiles, updated_files):
+        shebang_match = None
+        script = convert_path(script)
+        outfile = os.path.join(self.build_dir, os.path.basename(script))
+        outfiles.append(outfile)
+
+        if not self.force and not newer(script, outfile):
+            log.debug("not copying %s (up-to-date)", script)
+            return
+
+        # Always open the file, but ignore failures in dry-run mode
+        # in order to attempt to copy directly.
+        try:
+            f = tokenize.open(script)
+        except OSError:
+            if not self.dry_run:
+                raise
+            f = None
+        else:
+            first_line = f.readline()
+            if not first_line:
+                self.warn("%s is an empty file (skipping)" % script)
+                return
+
+            shebang_match = shebang_pattern.match(first_line)
+
+        updated_files.append(outfile)
+        if shebang_match:
+            log.info("copying and adjusting %s -> %s", script,
+                     self.build_dir)
+            if not self.dry_run:
+                if not sysconfig.python_build:
+                    executable = self.executable
+                else:
+                    executable = os.path.join(
+                        sysconfig.get_config_var("BINDIR"),
+                        "python%s%s" % (
+                            sysconfig.get_config_var("VERSION"),
+                            sysconfig.get_config_var("EXE")))
+                post_interp = shebang_match.group(1) or ''
+                shebang = "#!" + executable + post_interp + "\n"
+                self._validate_shebang(shebang, f.encoding)
+                with open(outfile, "w", encoding=f.encoding) as outf:
+                    outf.write(shebang)
+                    outf.writelines(f.readlines())
+            if f:
+                f.close()
+        else:
+            if f:
+                f.close()
+            self.copy_file(script, outfile)
+
+    def _change_modes(self, outfiles):
+        if os.name != 'posix':
+            return
+
+        for file in outfiles:
+            self._change_mode(file)
+
+    def _change_mode(self, file):
+        if self.dry_run:
+            log.info("changing mode of %s", file)
+            return
+
+        oldmode = os.stat(file)[ST_MODE] & 0o7777
+        newmode = (oldmode | 0o555) & 0o7777
+        if newmode != oldmode:
+            log.info("changing mode of %s from %o to %o",
+                     file, oldmode, newmode)
+            os.chmod(file, newmode)
+
+    @staticmethod
+    def _validate_shebang(shebang, encoding):
+        # Python parser starts to read a script using UTF-8 until
+        # it gets a #coding:xxx cookie. The shebang has to be the
+        # first line of a file, the #coding:xxx cookie cannot be
+        # written before. So the shebang has to be encodable to
+        # UTF-8.
+        try:
+            shebang.encode('utf-8')
+        except UnicodeEncodeError:
+            raise ValueError(
+                "The shebang ({!r}) is not encodable "
+                "to utf-8".format(shebang))
+
+        # If the script is encoded to a custom encoding (use a
+        # #coding:xxx cookie), the shebang has to be encodable to
+        # the script encoding too.
+        try:
+            shebang.encode(encoding)
+        except UnicodeEncodeError:
+            raise ValueError(
+                "The shebang ({!r}) is not encodable "
+                "to the script encoding ({})"
+                .format(shebang, encoding))
diff --git a/setuptools/_distutils/command/check.py b/setuptools/_distutils/command/check.py
index ada25006..af311ca9 100644
--- a/setuptools/_distutils/command/check.py
+++ b/setuptools/_distutils/command/check.py
@@ -2,6 +2,8 @@
 
 Implements the Distutils 'check' command.
 """
+from email.utils import getaddresses
+
 from distutils.core import Command
 from distutils.errors import DistutilsSetupError
 
@@ -17,7 +19,7 @@ try:
         def __init__(self, source, report_level, halt_level, stream=None,
                      debug=0, encoding='ascii', error_handler='replace'):
             self.messages = []
-            Reporter.__init__(self, source, report_level, halt_level, stream,
+            super().__init__(source, report_level, halt_level, stream,
                               debug, encoding, error_handler)
 
         def system_message(self, level, message, *children, **kwargs):
@@ -96,19 +98,39 @@ class check(Command):
 
         if missing:
             self.warn("missing required meta-data: %s"  % ', '.join(missing))
-        if metadata.author:
-            if not metadata.author_email:
-                self.warn("missing meta-data: if 'author' supplied, " +
-                          "'author_email' should be supplied too")
-        elif metadata.maintainer:
-            if not metadata.maintainer_email:
-                self.warn("missing meta-data: if 'maintainer' supplied, " +
-                          "'maintainer_email' should be supplied too")
-        else:
+        if not (
+            self._check_contact("author", metadata) or
+            self._check_contact("maintainer", metadata)
+        ):
             self.warn("missing meta-data: either (author and author_email) " +
                       "or (maintainer and maintainer_email) " +
                       "should be supplied")
 
+    def _check_contact(self, kind, metadata):
+        """
+        Returns True if the contact's name is specified and False otherwise.
+        This function will warn if the contact's email is not specified.
+        """
+        name = getattr(metadata, kind) or ''
+        email = getattr(metadata, kind + '_email') or ''
+
+        msg = ("missing meta-data: if '{}' supplied, " +
+               "'{}' should be supplied too")
+
+        if name and email:
+            return True
+
+        if name:
+            self.warn(msg.format(kind, kind + '_email'))
+            return True
+
+        addresses = [(alias, addr) for alias, addr in getaddresses([email])]
+        if any(alias and addr for alias, addr in addresses):
+            # The contact's name can be encoded in the email: `Name <email>`
+            return True
+
+        return False
+
     def check_restructuredtext(self):
         """Checks if the long string fields are reST-compliant."""
         data = self.distribution.get_long_description()
diff --git a/setuptools/_distutils/command/install.py b/setuptools/_distutils/command/install.py
index c756b6db..41c17d8a 100644
--- a/setuptools/_distutils/command/install.py
+++ b/setuptools/_distutils/command/install.py
@@ -17,6 +17,7 @@ from distutils.file_util import write_file
 from distutils.util import convert_path, subst_vars, change_root
 from distutils.util import get_platform
 from distutils.errors import DistutilsOptionError
+from .. import _collections
 
 from site import USER_BASE
 from site import USER_SITE
@@ -67,8 +68,8 @@ if HAS_USER_SITE:
     INSTALL_SCHEMES['nt_user'] = {
         'purelib': '{usersite}',
         'platlib': '{usersite}',
-        'headers': '{userbase}/{implementation}{py_version_nodot}/Include/{dist_name}',
-        'scripts': '{userbase}/{implementation}{py_version_nodot}/Scripts',
+        'headers': '{userbase}/{implementation}{py_version_nodot_plat}/Include/{dist_name}',
+        'scripts': '{userbase}/{implementation}{py_version_nodot_plat}/Scripts',
         'data'   : '{userbase}',
         }
 
@@ -118,6 +119,65 @@ def _get_implementation():
         return 'Python'
 
 
+def _select_scheme(ob, name):
+    scheme = _inject_headers(name, _load_scheme(_resolve_scheme(name)))
+    vars(ob).update(_remove_set(ob, _scheme_attrs(scheme)))
+
+
+def _remove_set(ob, attrs):
+    """
+    Include only attrs that are None in ob.
+    """
+    return {
+        key: value
+        for key, value in attrs.items()
+        if getattr(ob, key) is None
+    }
+
+
+def _resolve_scheme(name):
+    os_name, sep, key = name.partition('_')
+    try:
+        resolved = sysconfig.get_preferred_scheme(key)
+    except Exception:
+        resolved = _pypy_hack(name)
+    return resolved
+
+
+def _load_scheme(name):
+    return _load_schemes()[name]
+
+
+def _inject_headers(name, scheme):
+    """
+    Given a scheme name and the resolved scheme,
+    if the scheme does not include headers, resolve
+    the fallback scheme for the name and use headers
+    from it. pypa/distutils#88
+    """
+    # Bypass the preferred scheme, which may not
+    # have defined headers.
+    fallback = _load_scheme(_pypy_hack(name))
+    scheme.setdefault('headers', fallback['headers'])
+    return scheme
+
+
+def _scheme_attrs(scheme):
+    """Resolve install directories by applying the install schemes."""
+    return {
+        f'install_{key}': scheme[key]
+        for key in SCHEME_KEYS
+    }
+
+
+def _pypy_hack(name):
+    PY37 = sys.version_info < (3, 8)
+    old_pypy = hasattr(sys, 'pypy_version_info') and PY37
+    prefix = not name.endswith(('_user', '_home'))
+    pypy_name = 'pypy' + '_nt' * (os.name == 'nt')
+    return pypy_name if old_pypy and prefix else name
+
+
 class install(Command):
 
     description = "install everything from build directory"
@@ -335,25 +395,35 @@ class install(Command):
         except AttributeError:
             # sys.abiflags may not be defined on all platforms.
             abiflags = ''
-        self.config_vars = {'dist_name': self.distribution.get_name(),
-                            '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],
-                            'sys_prefix': prefix,
-                            'prefix': prefix,
-                            'sys_exec_prefix': exec_prefix,
-                            'exec_prefix': exec_prefix,
-                            'abiflags': abiflags,
-                            'platlibdir': getattr(sys, 'platlibdir', 'lib'),
-                            'implementation_lower': _get_implementation().lower(),
-                            'implementation': _get_implementation(),
-                           }
+        local_vars = {
+            'dist_name': self.distribution.get_name(),
+            '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],
+            'sys_prefix': prefix,
+            'prefix': prefix,
+            'sys_exec_prefix': exec_prefix,
+            'exec_prefix': exec_prefix,
+            'abiflags': abiflags,
+            'platlibdir': getattr(sys, 'platlibdir', 'lib'),
+            'implementation_lower': _get_implementation().lower(),
+            'implementation': _get_implementation(),
+        }
+
+        # vars for compatibility on older Pythons
+        compat_vars = dict(
+            # Python 3.9 and earlier
+            py_version_nodot_plat=getattr(sys, 'winver', '').replace('.', ''),
+        )
 
         if HAS_USER_SITE:
-            self.config_vars['userbase'] = self.install_userbase
-            self.config_vars['usersite'] = self.install_usersite
+            local_vars['userbase'] = self.install_userbase
+            local_vars['usersite'] = self.install_usersite
+
+        self.config_vars = _collections.DictStack(
+            [compat_vars, sysconfig.get_config_vars(), local_vars])
 
         self.expand_basedirs()
 
@@ -361,15 +431,13 @@ class install(Command):
 
         # Now define config vars for the base directories so we can expand
         # everything else.
-        self.config_vars['base'] = self.install_base
-        self.config_vars['platbase'] = self.install_platbase
-        self.config_vars['installed_base'] = (
-            sysconfig.get_config_vars()['installed_base'])
+        local_vars['base'] = self.install_base
+        local_vars['platbase'] = self.install_platbase
 
         if DEBUG:
             from pprint import pprint
             print("config vars:")
-            pprint(self.config_vars)
+            pprint(dict(self.config_vars))
 
         # Expand "~" and configuration variables in the installation
         # directories.
@@ -445,12 +513,17 @@ class install(Command):
     def finalize_unix(self):
         """Finalizes options for posix platforms."""
         if self.install_base is not None or self.install_platbase is not None:
-            if ((self.install_lib is None and
-                 self.install_purelib is None and
-                 self.install_platlib is None) or
+            incomplete_scheme = (
+                (
+                    self.install_lib is None and
+                    self.install_purelib is None and
+                    self.install_platlib is None
+                ) or
                 self.install_headers is None or
                 self.install_scripts is None or
-                self.install_data is None):
+                self.install_data is None
+            )
+            if incomplete_scheme:
                 raise DistutilsOptionError(
                       "install-base or install-platbase supplied, but "
                       "installation scheme is incomplete")
@@ -471,8 +544,13 @@ class install(Command):
                     raise DistutilsOptionError(
                           "must not supply exec-prefix without prefix")
 
-                self.prefix = os.path.normpath(sys.prefix)
-                self.exec_prefix = os.path.normpath(sys.exec_prefix)
+                # Allow Fedora to add components to the prefix
+                _prefix_addition = getattr(sysconfig, '_prefix_addition', "")
+
+                self.prefix = (
+                    os.path.normpath(sys.prefix) + _prefix_addition)
+                self.exec_prefix = (
+                    os.path.normpath(sys.exec_prefix) + _prefix_addition)
 
             else:
                 if self.exec_prefix is None:
@@ -505,20 +583,7 @@ class install(Command):
                       "I don't know how to install stuff on '%s'" % os.name)
 
     def select_scheme(self, name):
-        """Sets the install directories by applying the install schemes."""
-        # it's the caller's problem if they supply a bad name!
-        if (hasattr(sys, 'pypy_version_info') and
-                sys.version_info < (3, 8) and
-                not name.endswith(('_user', '_home'))):
-            if os.name == 'nt':
-                name = 'pypy_nt'
-            else:
-                name = 'pypy'
-        scheme = _load_schemes()[name]
-        for key in SCHEME_KEYS:
-            attrname = 'install_' + key
-            if getattr(self, attrname) is None:
-                setattr(self, attrname, scheme[key])
+        _select_scheme(self, name)
 
     def _expand_attrs(self, attrs):
         for attr in attrs:
@@ -592,7 +657,7 @@ class install(Command):
             return
         home = convert_path(os.path.expanduser("~"))
         for name, path in self.config_vars.items():
-            if path.startswith(home) and not os.path.isdir(path):
+            if str(path).startswith(home) and not os.path.isdir(path):
                 self.debug_print("os.makedirs('%s', 0o700)" % path)
                 os.makedirs(path, 0o700)
 
diff --git a/setuptools/_distutils/cygwinccompiler.py b/setuptools/_distutils/cygwinccompiler.py
index f80ca622..c5c86d8f 100644
--- a/setuptools/_distutils/cygwinccompiler.py
+++ b/setuptools/_distutils/cygwinccompiler.py
@@ -50,15 +50,15 @@ cygwin in no-cygwin mode).
 import os
 import sys
 import copy
-from subprocess import Popen, PIPE, check_output
-import re
+import shlex
+import warnings
+from subprocess import check_output
 
 from distutils.unixccompiler import UnixCCompiler
 from distutils.file_util import write_file
 from distutils.errors import (DistutilsExecError, CCompilerError,
         CompileError, UnknownFileError)
-from distutils.version import LooseVersion
-from distutils.spawn import find_executable
+from distutils.version import LooseVersion, suppress_known_deprecation
 
 def get_msvcr():
     """Include the appropriate MSVC runtime library if Python was built
@@ -108,7 +108,7 @@ class CygwinCCompiler(UnixCCompiler):
 
     def __init__(self, verbose=0, dry_run=0, force=0):
 
-        UnixCCompiler.__init__(self, verbose, dry_run, force)
+        super().__init__(verbose, dry_run, force)
 
         status, details = check_config_h()
         self.debug_print("Python's GCC status: %s (details: %s)" %
@@ -123,33 +123,8 @@ class CygwinCCompiler(UnixCCompiler):
         self.cc = os.environ.get('CC', 'gcc')
         self.cxx = os.environ.get('CXX', 'g++')
 
-        if ('gcc' in self.cc): # Start gcc workaround
-            self.gcc_version, self.ld_version, self.dllwrap_version = \
-                get_versions()
-            self.debug_print(self.compiler_type + ": gcc %s, ld %s, dllwrap %s\n" %
-                             (self.gcc_version,
-                              self.ld_version,
-                              self.dllwrap_version) )
-
-            # ld_version >= "2.10.90" and < "2.13" should also be able to use
-            # gcc -mdll instead of dllwrap
-            # Older dllwraps had own version numbers, newer ones use the
-            # same as the rest of binutils ( also ld )
-            # dllwrap 2.10.90 is buggy
-            if self.ld_version >= "2.10.90":
-                self.linker_dll = self.cc
-            else:
-                self.linker_dll = "dllwrap"
-
-            # ld_version >= "2.13" support -shared so use it instead of
-            # -mdll -static
-            if self.ld_version >= "2.13":
-                shared_option = "-shared"
-            else:
-                shared_option = "-mdll -static"
-        else: # Assume linker is up to date
-            self.linker_dll = self.cc
-            shared_option = "-shared"
+        self.linker_dll = self.cc
+        shared_option = "-shared"
 
         self.set_executables(compiler='%s -mcygwin -O -Wall' % self.cc,
                              compiler_so='%s -mcygwin -mdll -O -Wall' % self.cc,
@@ -158,17 +133,24 @@ class CygwinCCompiler(UnixCCompiler):
                              linker_so=('%s -mcygwin %s' %
                                         (self.linker_dll, shared_option)))
 
-        # cygwin and mingw32 need different sets of libraries
-        if ('gcc' in self.cc and self.gcc_version == "2.91.57"):
-            # cygwin shouldn't need msvcrt, but without the dlls will crash
-            # (gcc version 2.91.57) -- perhaps something about initialization
-            self.dll_libraries=["msvcrt"]
-            self.warn(
-                "Consider upgrading to a newer version of gcc")
-        else:
-            # Include the appropriate MSVC runtime library if Python was built
-            # with MSVC 7.0 or later.
-            self.dll_libraries = get_msvcr()
+        # Include the appropriate MSVC runtime library if Python was built
+        # with MSVC 7.0 or later.
+        self.dll_libraries = get_msvcr()
+
+    @property
+    def gcc_version(self):
+        # Older numpy dependend on this existing to check for ancient
+        # gcc versions. This doesn't make much sense with clang etc so
+        # just hardcode to something recent.
+        # https://github.com/numpy/numpy/pull/20333
+        warnings.warn(
+            "gcc_version attribute of CygwinCCompiler is deprecated. "
+            "Instead of returning actual gcc version a fixed value 11.2.0 is returned.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        with suppress_known_deprecation():
+            return LooseVersion("11.2.0")
 
     def _compile(self, obj, src, ext, cc_args, extra_postargs, pp_opts):
         """Compiles the source by spawning GCC and windres if needed."""
@@ -230,24 +212,17 @@ class CygwinCCompiler(UnixCCompiler):
 
             # next add options for def-file and to creating import libraries
 
-            # dllwrap uses different options than gcc/ld
-            if self.linker_dll == "dllwrap":
-                extra_preargs.extend(["--output-lib", lib_file])
-                # for dllwrap we have to use a special option
-                extra_preargs.extend(["--def", def_file])
-            # we use gcc/ld here and can be sure ld is >= 2.9.10
-            else:
-                # doesn't work: bfd_close build\...\libfoo.a: Invalid operation
-                #extra_preargs.extend(["-Wl,--out-implib,%s" % lib_file])
-                # for gcc/ld the def-file is specified as any object files
-                objects.append(def_file)
+            # doesn't work: bfd_close build\...\libfoo.a: Invalid operation
+            #extra_preargs.extend(["-Wl,--out-implib,%s" % lib_file])
+            # for gcc/ld the def-file is specified as any object files
+            objects.append(def_file)
 
         #end: if ((export_symbols is not None) and
         #        (target_desc != self.EXECUTABLE or self.linker_dll == "gcc")):
 
         # who wants symbols and a many times larger output file
         # should explicitly switch the debug mode on
-        # otherwise we let dllwrap/ld strip the output file
+        # otherwise we let ld strip the output file
         # (On my machine: 10KiB < stripped_file < ??100KiB
         #   unstripped_file = stripped_file + XXX KiB
         #  ( XXX=254 for a typical python extension))
@@ -293,21 +268,9 @@ class Mingw32CCompiler(CygwinCCompiler):
 
     def __init__(self, verbose=0, dry_run=0, force=0):
 
-        CygwinCCompiler.__init__ (self, verbose, dry_run, force)
-
-        # ld_version >= "2.13" support -shared so use it instead of
-        # -mdll -static
-        if ('gcc' in self.cc and self.ld_version < "2.13"):
-            shared_option = "-mdll -static"
-        else:
-            shared_option = "-shared"
+        super().__init__ (verbose, dry_run, force)
 
-        # A real mingw32 doesn't need to specify a different entry point,
-        # but cygwin 2.91.57 in no-cygwin-mode needs it.
-        if ('gcc' in self.cc and self.gcc_version <= "2.91.57"):
-            entry_point = '--entry _DllMain@12'
-        else:
-            entry_point = ''
+        shared_option = "-shared"
 
         if is_cygwincc(self.cc):
             raise CCompilerError(
@@ -317,9 +280,9 @@ class Mingw32CCompiler(CygwinCCompiler):
                              compiler_so='%s -mdll -O -Wall' % self.cc,
                              compiler_cxx='%s -O -Wall' % self.cxx,
                              linker_exe='%s' % self.cc,
-                             linker_so='%s %s %s'
-                                        % (self.linker_dll, shared_option,
-                                           entry_point))
+                             linker_so='%s %s'
+                                        % (self.linker_dll, shared_option))
+
         # Maybe we should also append -mthreads, but then the finished
         # dlls need another dll (mingwm10.dll see Mingw32 docs)
         # (-mthreads: Support thread-safe exception handling on `Mingw32')
@@ -386,38 +349,14 @@ def check_config_h():
         return (CONFIG_H_UNCERTAIN,
                 "couldn't read '%s': %s" % (fn, exc.strerror))
 
-RE_VERSION = re.compile(br'(\d+\.\d+(\.\d+)*)')
-
-def _find_exe_version(cmd):
-    """Find the version of an executable by running `cmd` in the shell.
-
-    If the command is not found, or the output does not match
-    `RE_VERSION`, returns None.
-    """
-    executable = cmd.split()[0]
-    if find_executable(executable) is None:
-        return None
-    out = Popen(cmd, shell=True, stdout=PIPE).stdout
-    try:
-        out_string = out.read()
-    finally:
-        out.close()
-    result = RE_VERSION.search(out_string)
-    if result is None:
-        return None
-    # LooseVersion works with strings
-    # so we need to decode our bytes
-    return LooseVersion(result.group(1).decode())
-
-def get_versions():
-    """ Try to find out the versions of gcc, ld and dllwrap.
-
-    If not possible it returns None for it.
-    """
-    commands = ['gcc -dumpversion', 'ld -v', 'dllwrap --version']
-    return tuple([_find_exe_version(cmd) for cmd in commands])
-
 def is_cygwincc(cc):
     '''Try to determine if the compiler that would be used is from cygwin.'''
-    out_string = check_output([cc, '-dumpmachine'])
+    out_string = check_output(shlex.split(cc) + ['-dumpmachine'])
     return out_string.strip().endswith(b'cygwin')
+
+
+get_versions = None
+"""
+A stand-in for the previous get_versions() function to prevent failures
+when monkeypatched. See pypa/setuptools#2969.
+"""
diff --git a/setuptools/_distutils/log.py b/setuptools/_distutils/log.py
index 8ef6b28e..a68b156b 100644
--- a/setuptools/_distutils/log.py
+++ b/setuptools/_distutils/log.py
@@ -3,13 +3,14 @@
 # The class here is styled after PEP 282 so that it could later be
 # replaced with a standard Python logging implementation.
 
+import sys
+
 DEBUG = 1
 INFO = 2
 WARN = 3
 ERROR = 4
 FATAL = 5
 
-import sys
 
 class Log:
 
@@ -54,6 +55,7 @@ class Log:
     def fatal(self, msg, *args):
         self._log(FATAL, msg, args)
 
+
 _global_log = Log()
 log = _global_log.log
 debug = _global_log.debug
@@ -62,12 +64,14 @@ warn = _global_log.warn
 error = _global_log.error
 fatal = _global_log.fatal
 
+
 def set_threshold(level):
     # return the old threshold for use from tests
     old = _global_log.threshold
     _global_log.threshold = level
     return old
 
+
 def set_verbosity(v):
     if v <= 0:
         set_threshold(WARN)
diff --git a/setuptools/_distutils/msvc9compiler.py b/setuptools/_distutils/msvc9compiler.py
index a1b3b02f..6b627383 100644
--- a/setuptools/_distutils/msvc9compiler.py
+++ b/setuptools/_distutils/msvc9compiler.py
@@ -291,8 +291,6 @@ def query_vcvarsall(version, arch="x86"):
 
 # More globals
 VERSION = get_build_version()
-if VERSION < 8.0:
-    raise DistutilsPlatformError("VC %0.1f is not supported by this module" % VERSION)
 # MACROS = MacroExpander(VERSION)
 
 class MSVCCompiler(CCompiler) :
@@ -326,7 +324,7 @@ class MSVCCompiler(CCompiler) :
     exe_extension = '.exe'
 
     def __init__(self, verbose=0, dry_run=0, force=0):
-        CCompiler.__init__ (self, verbose, dry_run, force)
+        super().__init__(verbose, dry_run, force)
         self.__version = VERSION
         self.__root = r"Software\Microsoft\VisualStudio"
         # self.__macros = MACROS
@@ -339,6 +337,8 @@ class MSVCCompiler(CCompiler) :
     def initialize(self, plat_name=None):
         # multi-init means we would need to check platform same each time...
         assert not self.initialized, "don't init multiple times"
+        if self.__version < 8.0:
+            raise DistutilsPlatformError("VC %0.1f is not supported by this module" % self.__version)
         if plat_name is None:
             plat_name = get_platform()
         # sanity check for platforms to prevent obscure errors later.
diff --git a/setuptools/_distutils/msvccompiler.py b/setuptools/_distutils/msvccompiler.py
index 2d447b85..e1367b89 100644
--- a/setuptools/_distutils/msvccompiler.py
+++ b/setuptools/_distutils/msvccompiler.py
@@ -228,7 +228,7 @@ class MSVCCompiler(CCompiler) :
     exe_extension = '.exe'
 
     def __init__(self, verbose=0, dry_run=0, force=0):
-        CCompiler.__init__ (self, verbose, dry_run, force)
+        super().__init__(verbose, dry_run, force)
         self.__version = get_build_version()
         self.__arch = get_build_architecture()
         if self.__arch == "Intel":
diff --git a/setuptools/_distutils/py39compat.py b/setuptools/_distutils/py39compat.py
new file mode 100644
index 00000000..9de95013
--- /dev/null
+++ b/setuptools/_distutils/py39compat.py
@@ -0,0 +1,21 @@
+import sys
+import platform
+
+
+def add_ext_suffix_39(vars):
+    """
+    Ensure vars contains 'EXT_SUFFIX'. pypa/distutils#130
+    """
+    import _imp
+    ext_suffix = _imp.extension_suffixes()[0]
+    vars.update(
+        EXT_SUFFIX=ext_suffix,
+        # sysconfig sets SO to match EXT_SUFFIX, so maintain
+        # that expectation.
+        # https://github.com/python/cpython/blob/785cc6770588de087d09e89a69110af2542be208/Lib/sysconfig.py#L671-L673
+        SO=ext_suffix,
+    )
+
+
+needs_ext_suffix = sys.version_info < (3, 10) and platform.system() == 'Windows'
+add_ext_suffix = add_ext_suffix_39 if needs_ext_suffix else lambda vars: None
diff --git a/setuptools/_distutils/spawn.py b/setuptools/_distutils/spawn.py
index 6e1c89f1..b2d10e39 100644
--- a/setuptools/_distutils/spawn.py
+++ b/setuptools/_distutils/spawn.py
@@ -10,7 +10,7 @@ import sys
 import os
 import subprocess
 
-from distutils.errors import DistutilsPlatformError, DistutilsExecError
+from distutils.errors import DistutilsExecError
 from distutils.debug import DEBUG
 from distutils import log
 
diff --git a/setuptools/_distutils/sysconfig.py b/setuptools/_distutils/sysconfig.py
index d36d94f7..55a42e16 100644
--- a/setuptools/_distutils/sysconfig.py
+++ b/setuptools/_distutils/sysconfig.py
@@ -9,12 +9,13 @@ Written by:   Fred L. Drake, Jr.
 Email:        <fdrake@acm.org>
 """
 
-import _imp
 import os
 import re
 import sys
+import sysconfig
 
 from .errors import DistutilsPlatformError
+from . import py39compat
 
 IS_PYPY = '__pypy__' in sys.builtin_module_names
 
@@ -47,6 +48,7 @@ def _is_python_source_dir(d):
             return True
     return False
 
+
 _sys_home = getattr(sys, '_home', None)
 
 if os.name == 'nt':
@@ -58,11 +60,13 @@ if os.name == 'nt':
     project_base = _fix_pcbuild(project_base)
     _sys_home = _fix_pcbuild(_sys_home)
 
+
 def _python_build():
     if _sys_home:
         return _is_python_source_dir(_sys_home)
     return _is_python_source_dir(project_base)
 
+
 python_build = _python_build()
 
 
@@ -78,6 +82,7 @@ except AttributeError:
     # this attribute, which is fine.
     pass
 
+
 def get_python_version():
     """Return a string containing the major and minor Python version,
     leaving off the patchlevel.  Sample return values could be '1.5'
@@ -191,7 +196,6 @@ def get_python_lib(plat_specific=0, standard_lib=0, prefix=None):
             "on platform '%s'" % os.name)
 
 
-
 def customize_compiler(compiler):
     """Do any platform-specific customization of a CCompiler instance.
 
@@ -216,8 +220,9 @@ def customize_compiler(compiler):
                 _config_vars['CUSTOMIZED_OSX_COMPILER'] = 'True'
 
         (cc, cxx, cflags, ccshared, ldshared, shlib_suffix, ar, ar_flags) = \
-            get_config_vars('CC', 'CXX', 'CFLAGS',
-                            'CCSHARED', 'LDSHARED', 'SHLIB_SUFFIX', 'AR', 'ARFLAGS')
+            get_config_vars(
+                'CC', 'CXX', 'CFLAGS',
+                'CCSHARED', 'LDSHARED', 'SHLIB_SUFFIX', 'AR', 'ARFLAGS')
 
         if 'CC' in os.environ:
             newcc = os.environ['CC']
@@ -274,31 +279,14 @@ def get_config_h_filename():
             inc_dir = os.path.join(_sys_home or project_base, "PC")
         else:
             inc_dir = _sys_home or project_base
+        return os.path.join(inc_dir, 'pyconfig.h')
     else:
-        inc_dir = get_python_inc(plat_specific=1)
-
-    return os.path.join(inc_dir, 'pyconfig.h')
-
-
-# Allow this value to be patched by pkgsrc. Ref pypa/distutils#16.
-_makefile_tmpl = 'config-{python_ver}{build_flags}{multiarch}'
+        return sysconfig.get_config_h_filename()
 
 
 def get_makefile_filename():
     """Return full pathname of installed Makefile from the Python build."""
-    if python_build:
-        return os.path.join(_sys_home or project_base, "Makefile")
-    lib_dir = get_python_lib(plat_specific=0, standard_lib=1)
-    multiarch = (
-        '-%s' % sys.implementation._multiarch
-        if hasattr(sys.implementation, '_multiarch') else ''
-    )
-    config_file = _makefile_tmpl.format(
-        python_ver=get_python_version(),
-        build_flags=build_flags,
-        multiarch=multiarch,
-    )
-    return os.path.join(lib_dir, config_file, 'Makefile')
+    return sysconfig.get_makefile_filename()
 
 
 def parse_config_h(fp, g=None):
@@ -308,26 +296,7 @@ def parse_config_h(fp, g=None):
     optional dictionary is passed in as the second argument, it is
     used instead of a new dictionary.
     """
-    if g is None:
-        g = {}
-    define_rx = re.compile("#define ([A-Z][A-Za-z0-9_]+) (.*)\n")
-    undef_rx = re.compile("/[*] #undef ([A-Z][A-Za-z0-9_]+) [*]/\n")
-    #
-    while True:
-        line = fp.readline()
-        if not line:
-            break
-        m = define_rx.match(line)
-        if m:
-            n, v = m.group(1, 2)
-            try: v = int(v)
-            except ValueError: pass
-            g[n] = v
-        else:
-            m = undef_rx.match(line)
-            if m:
-                g[m.group(1)] = 0
-    return g
+    return sysconfig.parse_config_h(fp, vars=g)
 
 
 # Regexes needed for parsing Makefile (and similar syntaxes,
@@ -336,6 +305,7 @@ _variable_rx = re.compile(r"([a-zA-Z][a-zA-Z0-9_]+)\s*=\s*(.*)")
 _findvar1_rx = re.compile(r"\$\(([A-Za-z][A-Za-z0-9_]*)\)")
 _findvar2_rx = re.compile(r"\${([A-Za-z][A-Za-z0-9_]*)}")
 
+
 def parse_makefile(fn, g=None):
     """Parse a Makefile-style file.
 
@@ -344,7 +314,9 @@ def parse_makefile(fn, g=None):
     used instead of a new dictionary.
     """
     from distutils.text_file import TextFile
-    fp = TextFile(fn, strip_comments=1, skip_blanks=1, join_lines=1, errors="surrogateescape")
+    fp = TextFile(
+        fn, strip_comments=1, skip_blanks=1, join_lines=1,
+        errors="surrogateescape")
 
     if g is None:
         g = {}
@@ -353,7 +325,7 @@ def parse_makefile(fn, g=None):
 
     while True:
         line = fp.readline()
-        if line is None: # eof
+        if line is None:  # eof
             break
         m = _variable_rx.match(line)
         if m:
@@ -397,7 +369,8 @@ def parse_makefile(fn, g=None):
                     item = os.environ[n]
 
                 elif n in renamed_variables:
-                    if name.startswith('PY_') and name[3:] in renamed_variables:
+                    if name.startswith('PY_') and \
+                            name[3:] in renamed_variables:
                         item = ""
 
                     elif 'PY_' + n in notdone:
@@ -413,7 +386,8 @@ def parse_makefile(fn, g=None):
                     if "$" in after:
                         notdone[name] = value
                     else:
-                        try: value = int(value)
+                        try:
+                            value = int(value)
                         except ValueError:
                             done[name] = value.strip()
                         else:
@@ -421,7 +395,7 @@ def parse_makefile(fn, g=None):
                         del notdone[name]
 
                         if name.startswith('PY_') \
-                            and name[3:] in renamed_variables:
+                                and name[3:] in renamed_variables:
 
                             name = name[3:]
                             if name not in done:
@@ -470,51 +444,6 @@ def expand_makefile_vars(s, vars):
 _config_vars = None
 
 
-_sysconfig_name_tmpl = '_sysconfigdata_{abi}_{platform}_{multiarch}'
-
-
-def _init_posix():
-    """Initialize the module as appropriate for POSIX systems."""
-    # _sysconfigdata is generated at build time, see the sysconfig module
-    name = os.environ.get(
-        '_PYTHON_SYSCONFIGDATA_NAME',
-        _sysconfig_name_tmpl.format(
-            abi=sys.abiflags,
-            platform=sys.platform,
-            multiarch=getattr(sys.implementation, '_multiarch', ''),
-        ),
-    )
-    try:
-        _temp = __import__(name, globals(), locals(), ['build_time_vars'], 0)
-    except ImportError:
-        # Python 3.5 and pypy 7.3.1
-        _temp = __import__(
-            '_sysconfigdata', globals(), locals(), ['build_time_vars'], 0)
-    build_time_vars = _temp.build_time_vars
-    global _config_vars
-    _config_vars = {}
-    _config_vars.update(build_time_vars)
-
-
-def _init_nt():
-    """Initialize the module as appropriate for NT"""
-    g = {}
-    # set basic install directories
-    g['LIBDEST'] = get_python_lib(plat_specific=0, standard_lib=1)
-    g['BINLIBDEST'] = get_python_lib(plat_specific=1, standard_lib=1)
-
-    # XXX hmmm.. a normal install puts include files here
-    g['INCLUDEPY'] = get_python_inc(plat_specific=0)
-
-    g['EXT_SUFFIX'] = _imp.extension_suffixes()[0]
-    g['EXE'] = ".exe"
-    g['VERSION'] = get_python_version().replace(".", "")
-    g['BINDIR'] = os.path.dirname(os.path.abspath(sys.executable))
-
-    global _config_vars
-    _config_vars = g
-
-
 def get_config_vars(*args):
     """With no arguments, return a dictionary of all configuration
     variables relevant for the current platform.  Generally this includes
@@ -527,60 +456,8 @@ def get_config_vars(*args):
     """
     global _config_vars
     if _config_vars is None:
-        func = globals().get("_init_" + os.name)
-        if func:
-            func()
-        else:
-            _config_vars = {}
-
-        # Normalized versions of prefix and exec_prefix are handy to have;
-        # in fact, these are the standard versions used most places in the
-        # Distutils.
-        _config_vars['prefix'] = PREFIX
-        _config_vars['exec_prefix'] = EXEC_PREFIX
-
-        if not IS_PYPY:
-            # For backward compatibility, see issue19555
-            SO = _config_vars.get('EXT_SUFFIX')
-            if SO is not None:
-                _config_vars['SO'] = SO
-
-            # Always convert srcdir to an absolute path
-            srcdir = _config_vars.get('srcdir', project_base)
-            if os.name == 'posix':
-                if python_build:
-                    # If srcdir is a relative path (typically '.' or '..')
-                    # then it should be interpreted relative to the directory
-                    # containing Makefile.
-                    base = os.path.dirname(get_makefile_filename())
-                    srcdir = os.path.join(base, srcdir)
-                else:
-                    # srcdir is not meaningful since the installation is
-                    # spread about the filesystem.  We choose the
-                    # directory containing the Makefile since we know it
-                    # exists.
-                    srcdir = os.path.dirname(get_makefile_filename())
-            _config_vars['srcdir'] = os.path.abspath(os.path.normpath(srcdir))
-
-            # Convert srcdir into an absolute path if it appears necessary.
-            # Normally it is relative to the build directory.  However, during
-            # testing, for example, we might be running a non-installed python
-            # from a different directory.
-            if python_build and os.name == "posix":
-                base = project_base
-                if (not os.path.isabs(_config_vars['srcdir']) and
-                    base != os.getcwd()):
-                    # srcdir is relative and we are not in the same directory
-                    # as the executable. Assume executable is in the build
-                    # directory and make srcdir absolute.
-                    srcdir = os.path.join(base, _config_vars['srcdir'])
-                    _config_vars['srcdir'] = os.path.normpath(srcdir)
-
-        # OS X platforms require special customization to handle
-        # multi-architecture, multi-os-version installers
-        if sys.platform == 'darwin':
-            import _osx_support
-            _osx_support.customize_config_vars(_config_vars)
+        _config_vars = sysconfig.get_config_vars().copy()
+        py39compat.add_ext_suffix(_config_vars)
 
     if args:
         vals = []
@@ -590,6 +467,7 @@ def get_config_vars(*args):
     else:
         return _config_vars
 
+
 def get_config_var(name):
     """Return the value of a single variable using the dictionary
     returned by 'get_config_vars()'.  Equivalent to
@@ -597,5 +475,6 @@ def get_config_var(name):
     """
     if name == 'SO':
         import warnings
-        warnings.warn('SO is deprecated, use EXT_SUFFIX', DeprecationWarning, 2)
+        warnings.warn(
+            'SO is deprecated, use EXT_SUFFIX', DeprecationWarning, 2)
     return get_config_vars().get(name)
diff --git a/setuptools/_distutils/tests/py38compat.py b/setuptools/_distutils/tests/py38compat.py
index 32269c7b..c949f58e 100644
--- a/setuptools/_distutils/tests/py38compat.py
+++ b/setuptools/_distutils/tests/py38compat.py
@@ -2,6 +2,11 @@
 
 import contextlib
 import builtins
+import sys
+
+from test.support import requires_zlib
+import test.support
+
 
 ModuleNotFoundError = getattr(builtins, 'ModuleNotFoundError', ImportError)
 
@@ -51,3 +56,7 @@ try:
     from test.support.warnings_helper import save_restore_warnings_filters
 except (ModuleNotFoundError, ImportError):
     save_restore_warnings_filters = _save_restore_warnings_filters
+
+
+if sys.version_info < (3, 9):
+    requires_zlib = lambda: test.support.requires_zlib
diff --git a/setuptools/_distutils/tests/test_archive_util.py b/setuptools/_distutils/tests/test_archive_util.py
index ce6456dc..800b9018 100644
--- a/setuptools/_distutils/tests/test_archive_util.py
+++ b/setuptools/_distutils/tests/test_archive_util.py
@@ -14,16 +14,11 @@ from distutils.archive_util import (check_archive_formats, make_tarball,
 from distutils.spawn import find_executable, spawn
 from distutils.tests import support
 from test.support import run_unittest, patch
+from .unix_compat import require_unix_id, require_uid_0, grp, pwd, UID_0_SUPPORT
 
 from .py38compat import change_cwd
 from .py38compat import check_warnings
 
-try:
-    import grp
-    import pwd
-    UID_GID_SUPPORT = True
-except ImportError:
-    UID_GID_SUPPORT = False
 
 try:
     import zipfile
@@ -339,7 +334,7 @@ class ArchiveUtilTestCase(support.TempdirManager,
     def test_make_archive_owner_group(self):
         # testing make_archive with owner and group, with various combinations
         # this works even if there's not gid/uid support
-        if UID_GID_SUPPORT:
+        if UID_0_SUPPORT:
             group = grp.getgrgid(0)[0]
             owner = pwd.getpwuid(0)[0]
         else:
@@ -364,7 +359,8 @@ class ArchiveUtilTestCase(support.TempdirManager,
         self.assertTrue(os.path.exists(res))
 
     @unittest.skipUnless(ZLIB_SUPPORT, "Requires zlib")
-    @unittest.skipUnless(UID_GID_SUPPORT, "Requires grp and pwd support")
+    @require_unix_id
+    @require_uid_0
     def test_tarfile_root_owner(self):
         tmpdir =  self._create_files()
         base_name = os.path.join(self.mkdtemp(), 'archive')
@@ -391,7 +387,7 @@ class ArchiveUtilTestCase(support.TempdirManager,
             archive.close()
 
 def test_suite():
-    return unittest.makeSuite(ArchiveUtilTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(ArchiveUtilTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_bdist.py b/setuptools/_distutils/tests/test_bdist.py
index 130d8bf1..8b7498e3 100644
--- a/setuptools/_distutils/tests/test_bdist.py
+++ b/setuptools/_distutils/tests/test_bdist.py
@@ -51,7 +51,7 @@ class BuildTestCase(support.TempdirManager,
 
 
 def test_suite():
-    return unittest.makeSuite(BuildTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(BuildTestCase)
 
 if __name__ == '__main__':
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_bdist_dumb.py b/setuptools/_distutils/tests/test_bdist_dumb.py
index 01a233bc..bb860c8a 100644
--- a/setuptools/_distutils/tests/test_bdist_dumb.py
+++ b/setuptools/_distutils/tests/test_bdist_dumb.py
@@ -91,7 +91,7 @@ class BuildDumbTestCase(support.TempdirManager,
         self.assertEqual(contents, sorted(wanted))
 
 def test_suite():
-    return unittest.makeSuite(BuildDumbTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(BuildDumbTestCase)
 
 if __name__ == '__main__':
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_bdist_msi.py b/setuptools/_distutils/tests/test_bdist_msi.py
index 937266f8..b1831ef2 100644
--- a/setuptools/_distutils/tests/test_bdist_msi.py
+++ b/setuptools/_distutils/tests/test_bdist_msi.py
@@ -22,7 +22,7 @@ class BDistMSITestCase(support.TempdirManager,
 
 
 def test_suite():
-    return unittest.makeSuite(BDistMSITestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(BDistMSITestCase)
 
 if __name__ == '__main__':
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_bdist_rpm.py b/setuptools/_distutils/tests/test_bdist_rpm.py
index 6453a02b..08a7cb46 100644
--- a/setuptools/_distutils/tests/test_bdist_rpm.py
+++ b/setuptools/_distutils/tests/test_bdist_rpm.py
@@ -3,13 +3,16 @@
 import unittest
 import sys
 import os
-from test.support import run_unittest, requires_zlib
+from test.support import run_unittest
 
 from distutils.core import Distribution
 from distutils.command.bdist_rpm import bdist_rpm
 from distutils.tests import support
 from distutils.spawn import find_executable
 
+from .py38compat import requires_zlib
+
+
 SETUP_PY = """\
 from distutils.core import setup
 import foo
@@ -44,7 +47,7 @@ class BuildRpmTestCase(support.TempdirManager,
     # spurious sdtout/stderr output under Mac OS X
     @unittest.skipUnless(sys.platform.startswith('linux'),
                          'spurious sdtout/stderr output under Mac OS X')
-    @requires_zlib
+    @requires_zlib()
     @unittest.skipIf(find_executable('rpm') is None,
                      'the rpm command is not found')
     @unittest.skipIf(find_executable('rpmbuild') is None,
@@ -87,7 +90,7 @@ class BuildRpmTestCase(support.TempdirManager,
     # spurious sdtout/stderr output under Mac OS X
     @unittest.skipUnless(sys.platform.startswith('linux'),
                          'spurious sdtout/stderr output under Mac OS X')
-    @requires_zlib
+    @requires_zlib()
     # http://bugs.python.org/issue1533164
     @unittest.skipIf(find_executable('rpm') is None,
                      'the rpm command is not found')
@@ -129,7 +132,7 @@ class BuildRpmTestCase(support.TempdirManager,
         os.remove(os.path.join(pkg_dir, 'dist', 'foo-0.1-1.noarch.rpm'))
 
 def test_suite():
-    return unittest.makeSuite(BuildRpmTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(BuildRpmTestCase)
 
 if __name__ == '__main__':
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_bdist_wininst.py b/setuptools/_distutils/tests/test_bdist_wininst.py
index 31cf2628..59f25167 100644
--- a/setuptools/_distutils/tests/test_bdist_wininst.py
+++ b/setuptools/_distutils/tests/test_bdist_wininst.py
@@ -34,7 +34,7 @@ class BuildWinInstTestCase(support.TempdirManager,
         self.assertGreater(len(exe_file), 10)
 
 def test_suite():
-    return unittest.makeSuite(BuildWinInstTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(BuildWinInstTestCase)
 
 if __name__ == '__main__':
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_build.py b/setuptools/_distutils/tests/test_build.py
index b020a5ba..93724419 100644
--- a/setuptools/_distutils/tests/test_build.py
+++ b/setuptools/_distutils/tests/test_build.py
@@ -24,10 +24,10 @@ class BuildTestCase(support.TempdirManager,
         wanted = os.path.join(cmd.build_base, 'lib')
         self.assertEqual(cmd.build_purelib, wanted)
 
-        # build_platlib is 'build/lib.platform-x.x[-pydebug]'
+        # build_platlib is 'build/lib.platform-cache_tag[-pydebug]'
         # examples:
-        #   build/lib.macosx-10.3-i386-2.7
-        plat_spec = '.%s-%d.%d' % (cmd.plat_name, *sys.version_info[:2])
+        #   build/lib.macosx-10.3-i386-cpython39
+        plat_spec = '.%s-%s' % (cmd.plat_name, sys.implementation.cache_tag)
         if hasattr(sys, 'gettotalrefcount'):
             self.assertTrue(cmd.build_platlib.endswith('-pydebug'))
             plat_spec += '-pydebug'
@@ -50,7 +50,7 @@ class BuildTestCase(support.TempdirManager,
         self.assertEqual(cmd.executable, os.path.normpath(sys.executable))
 
 def test_suite():
-    return unittest.makeSuite(BuildTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(BuildTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_build_clib.py b/setuptools/_distutils/tests/test_build_clib.py
index 259c4352..d50ead7c 100644
--- a/setuptools/_distutils/tests/test_build_clib.py
+++ b/setuptools/_distutils/tests/test_build_clib.py
@@ -130,7 +130,7 @@ class BuildCLibTestCase(support.TempdirManager,
         self.assertIn('libfoo.a', os.listdir(build_temp))
 
 def test_suite():
-    return unittest.makeSuite(BuildCLibTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(BuildCLibTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_build_ext.py b/setuptools/_distutils/tests/test_build_ext.py
index 85ecf4b7..920e4dc8 100644
--- a/setuptools/_distutils/tests/test_build_ext.py
+++ b/setuptools/_distutils/tests/test_build_ext.py
@@ -493,12 +493,16 @@ class BuildExtTestCase(TempdirManager,
         # format the target value as defined in the Apple
         # Availability Macros.  We can't use the macro names since
         # at least one value we test with will not exist yet.
-        if target[1] < 10:
+        if target[:2] < (10, 10):
             # for 10.1 through 10.9.x -> "10n0"
             target = '%02d%01d0' % target
         else:
             # for 10.10 and beyond -> "10nn00"
-            target = '%02d%02d00' % target
+            if len(target) >= 2:
+                target = '%02d%02d00' % target
+            else:
+                # 11 and later can have no minor version (11 instead of 11.0)
+                target = '%02d0000' % target
         deptarget_ext = Extension(
             'deptarget',
             [deptarget_c],
@@ -538,8 +542,8 @@ class ParallelBuildExtTestCase(BuildExtTestCase):
 
 def test_suite():
     suite = unittest.TestSuite()
-    suite.addTest(unittest.makeSuite(BuildExtTestCase))
-    suite.addTest(unittest.makeSuite(ParallelBuildExtTestCase))
+    suite.addTest(unittest.TestLoader().loadTestsFromTestCase(BuildExtTestCase))
+    suite.addTest(unittest.TestLoader().loadTestsFromTestCase(ParallelBuildExtTestCase))
     return suite
 
 if __name__ == '__main__':
diff --git a/setuptools/_distutils/tests/test_build_py.py b/setuptools/_distutils/tests/test_build_py.py
index 0712e92c..a590a485 100644
--- a/setuptools/_distutils/tests/test_build_py.py
+++ b/setuptools/_distutils/tests/test_build_py.py
@@ -173,7 +173,7 @@ class BuildPyTestCase(support.TempdirManager,
 
 
 def test_suite():
-    return unittest.makeSuite(BuildPyTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(BuildPyTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_build_scripts.py b/setuptools/_distutils/tests/test_build_scripts.py
index 954fc763..f299e51e 100644
--- a/setuptools/_distutils/tests/test_build_scripts.py
+++ b/setuptools/_distutils/tests/test_build_scripts.py
@@ -106,7 +106,7 @@ class BuildScriptsTestCase(support.TempdirManager,
             self.assertIn(name, built)
 
 def test_suite():
-    return unittest.makeSuite(BuildScriptsTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(BuildScriptsTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_check.py b/setuptools/_distutils/tests/test_check.py
index e534aca1..b41dba3d 100644
--- a/setuptools/_distutils/tests/test_check.py
+++ b/setuptools/_distutils/tests/test_check.py
@@ -71,6 +71,28 @@ class CheckTestCase(support.LoggingSilencer,
         cmd = self._run(metadata)
         self.assertEqual(cmd._warnings, 0)
 
+    def test_check_author_maintainer(self):
+        for kind in ("author", "maintainer"):
+            # ensure no warning when author_email or maintainer_email is given
+            # (the spec allows these fields to take the form "Name <email>")
+            metadata = {'url': 'xxx',
+                        kind + '_email': 'Name <name@email.com>',
+                        'name': 'xxx', 'version': 'xxx'}
+            cmd = self._run(metadata)
+            self.assertEqual(cmd._warnings, 0)
+
+            # the check should warn if only email is given and it does not
+            # contain the name
+            metadata[kind + '_email'] = 'name@email.com'
+            cmd = self._run(metadata)
+            self.assertEqual(cmd._warnings, 1)
+
+            # the check should warn if only the name is given
+            metadata[kind] = "Name"
+            del metadata[kind + '_email']
+            cmd = self._run(metadata)
+            self.assertEqual(cmd._warnings, 1)
+
     @unittest.skipUnless(HAS_DOCUTILS, "won't test without docutils")
     def test_check_document(self):
         pkg_info, dist = self.create_dist()
@@ -157,7 +179,7 @@ class CheckTestCase(support.LoggingSilencer,
                                  'restructuredtext': 1})
 
 def test_suite():
-    return unittest.makeSuite(CheckTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(CheckTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_clean.py b/setuptools/_distutils/tests/test_clean.py
index c605afd8..92367499 100644
--- a/setuptools/_distutils/tests/test_clean.py
+++ b/setuptools/_distutils/tests/test_clean.py
@@ -43,7 +43,7 @@ class cleanTestCase(support.TempdirManager,
         cmd.run()
 
 def test_suite():
-    return unittest.makeSuite(cleanTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(cleanTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_cmd.py b/setuptools/_distutils/tests/test_cmd.py
index cf5197c3..2319214a 100644
--- a/setuptools/_distutils/tests/test_cmd.py
+++ b/setuptools/_distutils/tests/test_cmd.py
@@ -120,7 +120,7 @@ class CommandTestCase(unittest.TestCase):
             debug.DEBUG = False
 
 def test_suite():
-    return unittest.makeSuite(CommandTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(CommandTestCase)
 
 if __name__ == '__main__':
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_config.py b/setuptools/_distutils/tests/test_config.py
index 344084af..27bd9d44 100644
--- a/setuptools/_distutils/tests/test_config.py
+++ b/setuptools/_distutils/tests/test_config.py
@@ -66,7 +66,7 @@ class BasePyPIRCCommandTestCase(support.TempdirManager,
 
         class command(PyPIRCCommand):
             def __init__(self, dist):
-                PyPIRCCommand.__init__(self, dist)
+                super().__init__(dist)
             def initialize_options(self):
                 pass
             finalize_options = initialize_options
@@ -135,7 +135,7 @@ class PyPIRCCommandTestCase(BasePyPIRCCommandTestCase):
 
 
 def test_suite():
-    return unittest.makeSuite(PyPIRCCommandTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(PyPIRCCommandTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_config_cmd.py b/setuptools/_distutils/tests/test_config_cmd.py
index 4cd9a6b9..2c84719a 100644
--- a/setuptools/_distutils/tests/test_config_cmd.py
+++ b/setuptools/_distutils/tests/test_config_cmd.py
@@ -92,7 +92,7 @@ class ConfigTestCase(support.LoggingSilencer,
             self.assertFalse(os.path.exists(f))
 
 def test_suite():
-    return unittest.makeSuite(ConfigTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(ConfigTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_core.py b/setuptools/_distutils/tests/test_core.py
index d99cfd26..7270d699 100644
--- a/setuptools/_distutils/tests/test_core.py
+++ b/setuptools/_distutils/tests/test_core.py
@@ -159,7 +159,7 @@ class CoreTestCase(support.EnvironGuard, unittest.TestCase):
         self.assertEqual(stdout.readlines()[0], wanted)
 
 def test_suite():
-    return unittest.makeSuite(CoreTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(CoreTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_cygwinccompiler.py b/setuptools/_distutils/tests/test_cygwinccompiler.py
index 2a02eed4..8715a535 100644
--- a/setuptools/_distutils/tests/test_cygwinccompiler.py
+++ b/setuptools/_distutils/tests/test_cygwinccompiler.py
@@ -2,28 +2,14 @@
 import unittest
 import sys
 import os
-from io import BytesIO
 from test.support import run_unittest
 
-from distutils import cygwinccompiler
 from distutils.cygwinccompiler import (check_config_h,
                                        CONFIG_H_OK, CONFIG_H_NOTOK,
-                                       CONFIG_H_UNCERTAIN, get_versions,
+                                       CONFIG_H_UNCERTAIN,
                                        get_msvcr)
 from distutils.tests import support
 
-class FakePopen(object):
-    test_class = None
-
-    def __init__(self, cmd, shell, stdout):
-        self.cmd = cmd.split()[0]
-        exes = self.test_class._exes
-        if self.cmd in exes:
-            # issue #6438 in Python 3.x, Popen returns bytes
-            self.stdout = BytesIO(exes[self.cmd])
-        else:
-            self.stdout = os.popen(cmd, 'r')
-
 
 class CygwinCCompilerTestCase(support.TempdirManager,
                               unittest.TestCase):
@@ -35,29 +21,16 @@ class CygwinCCompilerTestCase(support.TempdirManager,
         from distutils import sysconfig
         self.old_get_config_h_filename = sysconfig.get_config_h_filename
         sysconfig.get_config_h_filename = self._get_config_h_filename
-        self.old_find_executable = cygwinccompiler.find_executable
-        cygwinccompiler.find_executable = self._find_executable
-        self._exes = {}
-        self.old_popen = cygwinccompiler.Popen
-        FakePopen.test_class = self
-        cygwinccompiler.Popen = FakePopen
 
     def tearDown(self):
         sys.version = self.version
         from distutils import sysconfig
         sysconfig.get_config_h_filename = self.old_get_config_h_filename
-        cygwinccompiler.find_executable = self.old_find_executable
-        cygwinccompiler.Popen = self.old_popen
         super(CygwinCCompilerTestCase, self).tearDown()
 
     def _get_config_h_filename(self):
         return self.python_h
 
-    def _find_executable(self, name):
-        if name in self._exes:
-            return name
-        return None
-
     def test_check_config_h(self):
 
         # check_config_h looks for "GCC" in sys.version first
@@ -81,40 +54,6 @@ class CygwinCCompilerTestCase(support.TempdirManager,
         self.write_file(self.python_h, 'xxx __GNUC__ xxx')
         self.assertEqual(check_config_h()[0], CONFIG_H_OK)
 
-    def test_get_versions(self):
-
-        # get_versions calls distutils.spawn.find_executable on
-        # 'gcc', 'ld' and 'dllwrap'
-        self.assertEqual(get_versions(), (None, None, None))
-
-        # Let's fake we have 'gcc' and it returns '3.4.5'
-        self._exes['gcc'] = b'gcc (GCC) 3.4.5 (mingw special)\nFSF'
-        res = get_versions()
-        self.assertEqual(str(res[0]), '3.4.5')
-
-        # and let's see what happens when the version
-        # doesn't match the regular expression
-        # (\d+\.\d+(\.\d+)*)
-        self._exes['gcc'] = b'very strange output'
-        res = get_versions()
-        self.assertEqual(res[0], None)
-
-        # same thing for ld
-        self._exes['ld'] = b'GNU ld version 2.17.50 20060824'
-        res = get_versions()
-        self.assertEqual(str(res[1]), '2.17.50')
-        self._exes['ld'] = b'@(#)PROGRAM:ld  PROJECT:ld64-77'
-        res = get_versions()
-        self.assertEqual(res[1], None)
-
-        # and dllwrap
-        self._exes['dllwrap'] = b'GNU dllwrap 2.17.50 20060824\nFSF'
-        res = get_versions()
-        self.assertEqual(str(res[2]), '2.17.50')
-        self._exes['dllwrap'] = b'Cheese Wrap'
-        res = get_versions()
-        self.assertEqual(res[2], None)
-
     def test_get_msvcr(self):
 
         # none
@@ -151,7 +90,7 @@ class CygwinCCompilerTestCase(support.TempdirManager,
         self.assertRaises(ValueError, get_msvcr)
 
 def test_suite():
-    return unittest.makeSuite(CygwinCCompilerTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(CygwinCCompilerTestCase)
 
 if __name__ == '__main__':
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_dep_util.py b/setuptools/_distutils/tests/test_dep_util.py
index c6fae39c..0d52740a 100644
--- a/setuptools/_distutils/tests/test_dep_util.py
+++ b/setuptools/_distutils/tests/test_dep_util.py
@@ -74,7 +74,7 @@ class DepUtilTestCase(support.TempdirManager, unittest.TestCase):
 
 
 def test_suite():
-    return unittest.makeSuite(DepUtilTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(DepUtilTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_dir_util.py b/setuptools/_distutils/tests/test_dir_util.py
index d436cf83..1b1f3bbb 100644
--- a/setuptools/_distutils/tests/test_dir_util.py
+++ b/setuptools/_distutils/tests/test_dir_util.py
@@ -133,7 +133,7 @@ class DirUtilTestCase(support.TempdirManager, unittest.TestCase):
 
 
 def test_suite():
-    return unittest.makeSuite(DirUtilTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(DirUtilTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_dist.py b/setuptools/_distutils/tests/test_dist.py
index 45eadee8..36155be1 100644
--- a/setuptools/_distutils/tests/test_dist.py
+++ b/setuptools/_distutils/tests/test_dist.py
@@ -525,8 +525,8 @@ class MetadataTestCase(support.TempdirManager, support.EnvironGuard,
 
 def test_suite():
     suite = unittest.TestSuite()
-    suite.addTest(unittest.makeSuite(DistributionTestCase))
-    suite.addTest(unittest.makeSuite(MetadataTestCase))
+    suite.addTest(unittest.TestLoader().loadTestsFromTestCase(DistributionTestCase))
+    suite.addTest(unittest.TestLoader().loadTestsFromTestCase(MetadataTestCase))
     return suite
 
 if __name__ == "__main__":
diff --git a/setuptools/_distutils/tests/test_extension.py b/setuptools/_distutils/tests/test_extension.py
index 2eb5b422..78a55daa 100644
--- a/setuptools/_distutils/tests/test_extension.py
+++ b/setuptools/_distutils/tests/test_extension.py
@@ -65,7 +65,7 @@ class ExtensionTestCase(unittest.TestCase):
                           "Unknown Extension options: 'chic'")
 
 def test_suite():
-    return unittest.makeSuite(ExtensionTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(ExtensionTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_file_util.py b/setuptools/_distutils/tests/test_file_util.py
index d2536075..81b90d6c 100644
--- a/setuptools/_distutils/tests/test_file_util.py
+++ b/setuptools/_distutils/tests/test_file_util.py
@@ -118,7 +118,7 @@ class FileUtilTestCase(support.TempdirManager, unittest.TestCase):
 
 
 def test_suite():
-    return unittest.makeSuite(FileUtilTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(FileUtilTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_filelist.py b/setuptools/_distutils/tests/test_filelist.py
index 9ec507b5..a90edcf1 100644
--- a/setuptools/_distutils/tests/test_filelist.py
+++ b/setuptools/_distutils/tests/test_filelist.py
@@ -344,8 +344,8 @@ class FindAllTestCase(unittest.TestCase):
 
 def test_suite():
     return unittest.TestSuite([
-        unittest.makeSuite(FileListTestCase),
-        unittest.makeSuite(FindAllTestCase),
+        unittest.TestLoader().loadTestsFromTestCase(FileListTestCase),
+        unittest.TestLoader().loadTestsFromTestCase(FindAllTestCase),
     ])
 
 
diff --git a/setuptools/_distutils/tests/test_install.py b/setuptools/_distutils/tests/test_install.py
index cce973dc..3aef9e43 100644
--- a/setuptools/_distutils/tests/test_install.py
+++ b/setuptools/_distutils/tests/test_install.py
@@ -56,14 +56,15 @@ class InstallTestCase(support.TempdirManager,
             expected = os.path.normpath(expected)
             self.assertEqual(got, expected)
 
-        libdir = os.path.join(destination, "lib", "python")
+        impl_name = sys.implementation.name.replace("cpython", "python")
+        libdir = os.path.join(destination, "lib", impl_name)
         check_path(cmd.install_lib, libdir)
         _platlibdir = getattr(sys, "platlibdir", "lib")
-        platlibdir = os.path.join(destination, _platlibdir, "python")
+        platlibdir = os.path.join(destination, _platlibdir, impl_name)
         check_path(cmd.install_platlib, platlibdir)
         check_path(cmd.install_purelib, libdir)
         check_path(cmd.install_headers,
-                   os.path.join(destination, "include", "python", "foopkg"))
+                   os.path.join(destination, "include", impl_name, "foopkg"))
         check_path(cmd.install_scripts, os.path.join(destination, "bin"))
         check_path(cmd.install_data, destination)
 
@@ -81,7 +82,9 @@ class InstallTestCase(support.TempdirManager,
         install_module.USER_SITE = self.user_site
 
         def _expanduser(path):
-            return self.tmpdir
+            if path.startswith('~'):
+                return os.path.normpath(self.tmpdir + path[1:])
+            return path
         self.old_expand = os.path.expanduser
         os.path.expanduser = _expanduser
 
@@ -122,6 +125,17 @@ class InstallTestCase(support.TempdirManager,
         self.assertIn('userbase', cmd.config_vars)
         self.assertIn('usersite', cmd.config_vars)
 
+        actual_headers = os.path.relpath(cmd.install_headers, self.user_base)
+        if os.name == 'nt':
+            site_path = os.path.relpath(
+                os.path.dirname(self.old_user_site), self.old_user_base)
+            include = os.path.join(site_path, 'Include')
+        else:
+            include = sysconfig.get_python_inc(0, '')
+        expect_headers = os.path.join(include, 'xx')
+
+        self.assertEqual(os.path.normcase(actual_headers), os.path.normcase(expect_headers))
+
     def test_handle_extra_path(self):
         dist = Distribution({'name': 'xx', 'extra_path': 'path,dirs'})
         cmd = install(dist)
@@ -244,7 +258,7 @@ class InstallTestCase(support.TempdirManager,
 
 
 def test_suite():
-    return unittest.makeSuite(InstallTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(InstallTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_install_data.py b/setuptools/_distutils/tests/test_install_data.py
index 32ab296a..6191d2fa 100644
--- a/setuptools/_distutils/tests/test_install_data.py
+++ b/setuptools/_distutils/tests/test_install_data.py
@@ -69,7 +69,7 @@ class InstallDataTestCase(support.TempdirManager,
         self.assertTrue(os.path.exists(os.path.join(inst, rone)))
 
 def test_suite():
-    return unittest.makeSuite(InstallDataTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(InstallDataTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_install_headers.py b/setuptools/_distutils/tests/test_install_headers.py
index 2217b321..1aa4d09c 100644
--- a/setuptools/_distutils/tests/test_install_headers.py
+++ b/setuptools/_distutils/tests/test_install_headers.py
@@ -33,7 +33,7 @@ class InstallHeadersTestCase(support.TempdirManager,
         self.assertEqual(len(cmd.get_outputs()), 2)
 
 def test_suite():
-    return unittest.makeSuite(InstallHeadersTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(InstallHeadersTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_install_lib.py b/setuptools/_distutils/tests/test_install_lib.py
index fda6315b..652653f2 100644
--- a/setuptools/_distutils/tests/test_install_lib.py
+++ b/setuptools/_distutils/tests/test_install_lib.py
@@ -109,7 +109,7 @@ class InstallLibTestCase(support.TempdirManager,
 
 
 def test_suite():
-    return unittest.makeSuite(InstallLibTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(InstallLibTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_install_scripts.py b/setuptools/_distutils/tests/test_install_scripts.py
index 1f7b1038..648db3b1 100644
--- a/setuptools/_distutils/tests/test_install_scripts.py
+++ b/setuptools/_distutils/tests/test_install_scripts.py
@@ -76,7 +76,7 @@ class InstallScriptsTestCase(support.TempdirManager,
 
 
 def test_suite():
-    return unittest.makeSuite(InstallScriptsTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(InstallScriptsTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_log.py b/setuptools/_distutils/tests/test_log.py
index 75cf9006..ec2ae028 100644
--- a/setuptools/_distutils/tests/test_log.py
+++ b/setuptools/_distutils/tests/test_log.py
@@ -40,7 +40,7 @@ class TestLog(unittest.TestCase):
                         'Fαtal\t\\xc8rr\\u014dr')
 
 def test_suite():
-    return unittest.makeSuite(TestLog)
+    return unittest.TestLoader().loadTestsFromTestCase(TestLog)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_msvc9compiler.py b/setuptools/_distutils/tests/test_msvc9compiler.py
index 77a07ef3..6235405e 100644
--- a/setuptools/_distutils/tests/test_msvc9compiler.py
+++ b/setuptools/_distutils/tests/test_msvc9compiler.py
@@ -178,7 +178,7 @@ class msvc9compilerTestCase(support.TempdirManager,
 
 
 def test_suite():
-    return unittest.makeSuite(msvc9compilerTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(msvc9compilerTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_msvccompiler.py b/setuptools/_distutils/tests/test_msvccompiler.py
index 46a51cd0..846e5bb8 100644
--- a/setuptools/_distutils/tests/test_msvccompiler.py
+++ b/setuptools/_distutils/tests/test_msvccompiler.py
@@ -98,7 +98,7 @@ class TestSpawn(unittest.TestCase):
         compiler = _msvccompiler.MSVCCompiler()
         compiler._paths = "expected"
         inner_cmd = 'import os; assert os.environ["PATH"] == "expected"'
-        command = ['python', '-c', inner_cmd]
+        command = [sys.executable, '-c', inner_cmd]
 
         threads = [
             CheckThread(target=compiler.spawn, args=[command])
@@ -132,7 +132,7 @@ class TestSpawn(unittest.TestCase):
 
 
 def test_suite():
-    return unittest.makeSuite(msvccompilerTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(msvccompilerTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_register.py b/setuptools/_distutils/tests/test_register.py
index 84607f99..5770ed58 100644
--- a/setuptools/_distutils/tests/test_register.py
+++ b/setuptools/_distutils/tests/test_register.py
@@ -319,7 +319,7 @@ class RegisterTestCase(BasePyPIRCCommandTestCase):
 
 
 def test_suite():
-    return unittest.makeSuite(RegisterTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(RegisterTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_sdist.py b/setuptools/_distutils/tests/test_sdist.py
index b087a817..4c51717c 100644
--- a/setuptools/_distutils/tests/test_sdist.py
+++ b/setuptools/_distutils/tests/test_sdist.py
@@ -7,6 +7,7 @@ import zipfile
 from os.path import join
 from textwrap import dedent
 from test.support import captured_stdout, run_unittest
+from .unix_compat import require_unix_id, require_uid_0, pwd, grp
 
 from .py38compat import check_warnings
 
@@ -16,13 +17,6 @@ try:
 except ImportError:
     ZLIB_SUPPORT = False
 
-try:
-    import grp
-    import pwd
-    UID_GID_SUPPORT = True
-except ImportError:
-    UID_GID_SUPPORT = False
-
 from distutils.command.sdist import sdist, show_formats
 from distutils.core import Distribution
 from distutils.tests.test_config import BasePyPIRCCommandTestCase
@@ -440,7 +434,8 @@ class SDistTestCase(BasePyPIRCCommandTestCase):
                                              'fake-1.0/README.manual'])
 
     @unittest.skipUnless(ZLIB_SUPPORT, "requires zlib")
-    @unittest.skipUnless(UID_GID_SUPPORT, "Requires grp and pwd support")
+    @require_unix_id
+    @require_uid_0
     @unittest.skipIf(find_executable('tar') is None,
                      "The tar command is not found")
     @unittest.skipIf(find_executable('gzip') is None,
@@ -488,7 +483,7 @@ class SDistTestCase(BasePyPIRCCommandTestCase):
             archive.close()
 
 def test_suite():
-    return unittest.makeSuite(SDistTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(SDistTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_spawn.py b/setuptools/_distutils/tests/test_spawn.py
index f620da78..c5ed8e2b 100644
--- a/setuptools/_distutils/tests/test_spawn.py
+++ b/setuptools/_distutils/tests/test_spawn.py
@@ -133,7 +133,7 @@ class SpawnTestCase(support.TempdirManager,
 
 
 def test_suite():
-    return unittest.makeSuite(SpawnTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(SpawnTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_sysconfig.py b/setuptools/_distutils/tests/test_sysconfig.py
index 80cd1599..e671f9e0 100644
--- a/setuptools/_distutils/tests/test_sysconfig.py
+++ b/setuptools/_distutils/tests/test_sysconfig.py
@@ -38,6 +38,14 @@ class SysconfigTestCase(support.EnvironGuard, unittest.TestCase):
         config_h = sysconfig.get_config_h_filename()
         self.assertTrue(os.path.isfile(config_h), config_h)
 
+    @unittest.skipIf(sys.platform == 'win32',
+                     'Makefile only exists on Unix like systems')
+    @unittest.skipIf(sys.implementation.name != 'cpython',
+                     'Makefile only exists in CPython')
+    def test_get_makefile_filename(self):
+        makefile = sysconfig.get_makefile_filename()
+        self.assertTrue(os.path.isfile(makefile), makefile)
+
     def test_get_python_lib(self):
         # XXX doesn't work on Linux when Python was never installed before
         #self.assertTrue(os.path.isdir(lib_dir), lib_dir)
@@ -283,10 +291,27 @@ class SysconfigTestCase(support.EnvironGuard, unittest.TestCase):
         outs, errs = p.communicate()
         self.assertEqual(0, p.returncode, "Subprocess failed: " + outs)
 
+    def test_parse_config_h(self):
+        config_h = sysconfig.get_config_h_filename()
+        input = {}
+        with open(config_h, encoding="utf-8") as f:
+            result = sysconfig.parse_config_h(f, g=input)
+        self.assertTrue(input is result)
+        with open(config_h, encoding="utf-8") as f:
+            result = sysconfig.parse_config_h(f)
+        self.assertTrue(isinstance(result, dict))
+
+    @unittest.skipUnless(sys.platform == 'win32',
+                     'Testing windows pyd suffix')
+    @unittest.skipUnless(sys.implementation.name == 'cpython',
+                     'Need cpython for this test')
+    def test_win_ext_suffix(self):
+        self.assertTrue(sysconfig.get_config_var("EXT_SUFFIX").endswith(".pyd"))
+        self.assertNotEqual(sysconfig.get_config_var("EXT_SUFFIX"), ".pyd")
 
 def test_suite():
     suite = unittest.TestSuite()
-    suite.addTest(unittest.makeSuite(SysconfigTestCase))
+    suite.addTest(unittest.TestLoader().loadTestsFromTestCase(SysconfigTestCase))
     return suite
 
 
diff --git a/setuptools/_distutils/tests/test_text_file.py b/setuptools/_distutils/tests/test_text_file.py
index 7e76240a..ebac3d52 100644
--- a/setuptools/_distutils/tests/test_text_file.py
+++ b/setuptools/_distutils/tests/test_text_file.py
@@ -101,7 +101,7 @@ class TextFileTestCase(support.TempdirManager, unittest.TestCase):
             in_file.close()
 
 def test_suite():
-    return unittest.makeSuite(TextFileTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(TextFileTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_unixccompiler.py b/setuptools/_distutils/tests/test_unixccompiler.py
index 63c7dd37..c8b4c149 100644
--- a/setuptools/_distutils/tests/test_unixccompiler.py
+++ b/setuptools/_distutils/tests/test_unixccompiler.py
@@ -3,6 +3,7 @@ import os
 import sys
 import unittest
 from test.support import run_unittest
+from unittest.mock import patch
 
 from .py38compat import EnvironmentVarGuard
 
@@ -11,9 +12,12 @@ from distutils.errors import DistutilsPlatformError
 from distutils.unixccompiler import UnixCCompiler
 from distutils.util import _clear_cached_macosx_ver
 
-class UnixCCompilerTestCase(unittest.TestCase):
+from . import support
+
+class UnixCCompilerTestCase(support.TempdirManager, unittest.TestCase):
 
     def setUp(self):
+        super().setUp()
         self._backup_platform = sys.platform
         self._backup_get_config_var = sysconfig.get_config_var
         self._backup_get_config_vars = sysconfig.get_config_vars
@@ -23,6 +27,7 @@ class UnixCCompilerTestCase(unittest.TestCase):
         self.cc = CompilerWrapper()
 
     def tearDown(self):
+        super().tearDown()
         sys.platform = self._backup_platform
         sysconfig.get_config_var = self._backup_get_config_var
         sysconfig.get_config_vars = self._backup_get_config_vars
@@ -211,6 +216,42 @@ class UnixCCompilerTestCase(unittest.TestCase):
         self.assertEqual(self.cc.linker_so[0], 'my_cc')
 
     @unittest.skipIf(sys.platform == 'win32', "can't test on Windows")
+    def test_cc_overrides_ldshared_for_cxx_correctly(self):
+        """
+        Ensure that setting CC env variable also changes default linker
+        correctly when building C++ extensions.
+
+        pypa/distutils#126
+        """
+        def gcv(v):
+            if v == 'LDSHARED':
+                return 'gcc-4.2 -bundle -undefined dynamic_lookup '
+            elif v == 'CXX':
+                return 'g++-4.2'
+            return 'gcc-4.2'
+
+        def gcvs(*args, _orig=sysconfig.get_config_vars):
+            if args:
+                return list(map(sysconfig.get_config_var, args))
+            return _orig()
+
+        sysconfig.get_config_var = gcv
+        sysconfig.get_config_vars = gcvs
+        with patch.object(self.cc, 'spawn', return_value=None) as mock_spawn, \
+                patch.object(self.cc, '_need_link', return_value=True), \
+                patch.object(self.cc, 'mkpath', return_value=None), \
+                EnvironmentVarGuard() as env:
+            env['CC'] = 'ccache my_cc'
+            env['CXX'] = 'my_cxx'
+            del env['LDSHARED']
+            sysconfig.customize_compiler(self.cc)
+            self.assertEqual(self.cc.linker_so[0:2], ['ccache', 'my_cc'])
+            self.cc.link(None, [], 'a.out', target_lang='c++')
+            call_args = mock_spawn.call_args[0][0]
+            expected = ['my_cxx', '-bundle', '-undefined', 'dynamic_lookup']
+            assert call_args[:4] == expected
+
+    @unittest.skipIf(sys.platform == 'win32', "can't test on Windows")
     def test_explicit_ldshared(self):
         # Issue #18080:
         # ensure that setting CC env variable does not change
@@ -237,11 +278,12 @@ class UnixCCompilerTestCase(unittest.TestCase):
         # ensure that setting output_dir does not raise
         # FileNotFoundError: [Errno 2] No such file or directory: 'a.out'
         self.cc.output_dir = 'scratch'
+        os.chdir(self.mkdtemp())
         self.cc.has_function('abort', includes=['stdlib.h'])
 
 
 def test_suite():
-    return unittest.makeSuite(UnixCCompilerTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(UnixCCompilerTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_upload.py b/setuptools/_distutils/tests/test_upload.py
index bca5516d..ce3e84a2 100644
--- a/setuptools/_distutils/tests/test_upload.py
+++ b/setuptools/_distutils/tests/test_upload.py
@@ -217,7 +217,7 @@ class uploadTestCase(BasePyPIRCCommandTestCase):
 
 
 def test_suite():
-    return unittest.makeSuite(uploadTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(uploadTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_util.py b/setuptools/_distutils/tests/test_util.py
index bf0d4333..2738388e 100644
--- a/setuptools/_distutils/tests/test_util.py
+++ b/setuptools/_distutils/tests/test_util.py
@@ -2,6 +2,7 @@
 import os
 import sys
 import unittest
+import sysconfig as stdlib_sysconfig
 from copy import copy
 from test.support import run_unittest
 from unittest import mock
@@ -10,12 +11,10 @@ from distutils.errors import DistutilsPlatformError, DistutilsByteCompileError
 from distutils.util import (get_platform, convert_path, change_root,
                             check_environ, split_quoted, strtobool,
                             rfc822_escape, byte_compile,
-                            grok_environment_error)
+                            grok_environment_error, get_host_platform)
 from distutils import util # used to patch _environ_checked
-from distutils.sysconfig import get_config_vars
 from distutils import sysconfig
 from distutils.tests import support
-import _osx_support
 
 class UtilTestCase(support.EnvironGuard, unittest.TestCase):
 
@@ -63,110 +62,26 @@ class UtilTestCase(support.EnvironGuard, unittest.TestCase):
     def _get_uname(self):
         return self._uname
 
-    def test_get_platform(self):
-
-        # windows XP, 32bits
-        os.name = 'nt'
-        sys.version = ('2.4.4 (#71, Oct 18 2006, 08:34:43) '
-                       '[MSC v.1310 32 bit (Intel)]')
-        sys.platform = 'win32'
-        self.assertEqual(get_platform(), 'win32')
-
-        # windows XP, amd64
-        os.name = 'nt'
-        sys.version = ('2.4.4 (#71, Oct 18 2006, 08:34:43) '
-                       '[MSC v.1310 32 bit (Amd64)]')
-        sys.platform = 'win32'
-        self.assertEqual(get_platform(), 'win-amd64')
-
-        # macbook
-        os.name = 'posix'
-        sys.version = ('2.5 (r25:51918, Sep 19 2006, 08:49:13) '
-                       '\n[GCC 4.0.1 (Apple Computer, Inc. build 5341)]')
-        sys.platform = 'darwin'
-        self._set_uname(('Darwin', 'macziade', '8.11.1',
-                   ('Darwin Kernel Version 8.11.1: '
-                    'Wed Oct 10 18:23:28 PDT 2007; '
-                    'root:xnu-792.25.20~1/RELEASE_I386'), 'i386'))
-        _osx_support._remove_original_values(get_config_vars())
-        get_config_vars()['MACOSX_DEPLOYMENT_TARGET'] = '10.3'
-
-        get_config_vars()['CFLAGS'] = ('-fno-strict-aliasing -DNDEBUG -g '
-                                       '-fwrapv -O3 -Wall -Wstrict-prototypes')
-
-        cursize = sys.maxsize
-        sys.maxsize = (2 ** 31)-1
-        try:
-            self.assertEqual(get_platform(), 'macosx-10.3-i386')
-        finally:
-            sys.maxsize = cursize
-
-        # macbook with fat binaries (fat, universal or fat64)
-        _osx_support._remove_original_values(get_config_vars())
-        get_config_vars()['MACOSX_DEPLOYMENT_TARGET'] = '10.4'
-        get_config_vars()['CFLAGS'] = ('-arch ppc -arch i386 -isysroot '
-                                       '/Developer/SDKs/MacOSX10.4u.sdk  '
-                                       '-fno-strict-aliasing -fno-common '
-                                       '-dynamic -DNDEBUG -g -O3')
-
-        self.assertEqual(get_platform(), 'macosx-10.4-fat')
-
-        _osx_support._remove_original_values(get_config_vars())
-        os.environ['MACOSX_DEPLOYMENT_TARGET'] = '10.1'
-        self.assertEqual(get_platform(), 'macosx-10.4-fat')
-
+    def test_get_host_platform(self):
+        with unittest.mock.patch('os.name', 'nt'):
+             with unittest.mock.patch('sys.version', '... [... (ARM64)]'):
+                self.assertEqual(get_host_platform(), 'win-arm64')
+             with unittest.mock.patch('sys.version', '... [... (ARM)]'):
+                self.assertEqual(get_host_platform(), 'win-arm32')
 
-        _osx_support._remove_original_values(get_config_vars())
-        get_config_vars()['CFLAGS'] = ('-arch x86_64 -arch i386 -isysroot '
-                                       '/Developer/SDKs/MacOSX10.4u.sdk  '
-                                       '-fno-strict-aliasing -fno-common '
-                                       '-dynamic -DNDEBUG -g -O3')
+        with unittest.mock.patch('sys.version_info', (3, 9, 0, 'final', 0)):
+            self.assertEqual(get_host_platform(), stdlib_sysconfig.get_platform())
 
-        self.assertEqual(get_platform(), 'macosx-10.4-intel')
-
-        _osx_support._remove_original_values(get_config_vars())
-        get_config_vars()['CFLAGS'] = ('-arch x86_64 -arch ppc -arch i386 -isysroot '
-                                       '/Developer/SDKs/MacOSX10.4u.sdk  '
-                                       '-fno-strict-aliasing -fno-common '
-                                       '-dynamic -DNDEBUG -g -O3')
-        self.assertEqual(get_platform(), 'macosx-10.4-fat3')
-
-        _osx_support._remove_original_values(get_config_vars())
-        get_config_vars()['CFLAGS'] = ('-arch ppc64 -arch x86_64 -arch ppc -arch i386 -isysroot '
-                                       '/Developer/SDKs/MacOSX10.4u.sdk  '
-                                       '-fno-strict-aliasing -fno-common '
-                                       '-dynamic -DNDEBUG -g -O3')
-        self.assertEqual(get_platform(), 'macosx-10.4-universal')
-
-        _osx_support._remove_original_values(get_config_vars())
-        get_config_vars()['CFLAGS'] = ('-arch x86_64 -arch ppc64 -isysroot '
-                                       '/Developer/SDKs/MacOSX10.4u.sdk  '
-                                       '-fno-strict-aliasing -fno-common '
-                                       '-dynamic -DNDEBUG -g -O3')
-
-        self.assertEqual(get_platform(), 'macosx-10.4-fat64')
-
-        for arch in ('ppc', 'i386', 'x86_64', 'ppc64'):
-            _osx_support._remove_original_values(get_config_vars())
-            get_config_vars()['CFLAGS'] = ('-arch %s -isysroot '
-                                           '/Developer/SDKs/MacOSX10.4u.sdk  '
-                                           '-fno-strict-aliasing -fno-common '
-                                           '-dynamic -DNDEBUG -g -O3'%(arch,))
-
-            self.assertEqual(get_platform(), 'macosx-10.4-%s'%(arch,))
-
-
-        # linux debian sarge
-        os.name = 'posix'
-        sys.version = ('2.3.5 (#1, Jul  4 2007, 17:28:59) '
-                       '\n[GCC 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)]')
-        sys.platform = 'linux2'
-        self._set_uname(('Linux', 'aglae', '2.6.21.1dedibox-r7',
-                    '#1 Mon Apr 30 17:25:38 CEST 2007', 'i686'))
-
-        self.assertEqual(get_platform(), 'linux-i686')
-
-        # XXX more platforms to tests here
+    def test_get_platform(self):
+        with unittest.mock.patch('os.name', 'nt'):
+            with unittest.mock.patch.dict('os.environ', {'VSCMD_ARG_TGT_ARCH': 'x86'}):
+                 self.assertEqual(get_platform(), 'win32')
+            with unittest.mock.patch.dict('os.environ', {'VSCMD_ARG_TGT_ARCH': 'x64'}):
+                 self.assertEqual(get_platform(), 'win-amd64')
+            with unittest.mock.patch.dict('os.environ', {'VSCMD_ARG_TGT_ARCH': 'arm'}):
+                 self.assertEqual(get_platform(), 'win-arm32')
+            with unittest.mock.patch.dict('os.environ', {'VSCMD_ARG_TGT_ARCH': 'arm64'}):
+                 self.assertEqual(get_platform(), 'win-arm64')
 
     def test_convert_path(self):
         # linux/mac
@@ -303,7 +218,7 @@ class UtilTestCase(support.EnvironGuard, unittest.TestCase):
 
 
 def test_suite():
-    return unittest.makeSuite(UtilTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(UtilTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/test_version.py b/setuptools/_distutils/tests/test_version.py
index 8671cd2f..8405aa3a 100644
--- a/setuptools/_distutils/tests/test_version.py
+++ b/setuptools/_distutils/tests/test_version.py
@@ -1,11 +1,19 @@
 """Tests for distutils.version."""
 import unittest
+import distutils
 from distutils.version import LooseVersion
 from distutils.version import StrictVersion
 from test.support import run_unittest
 
 class VersionTestCase(unittest.TestCase):
 
+    def setUp(self):
+        self.ctx = distutils.version.suppress_known_deprecation()
+        self.ctx.__enter__()
+
+    def tearDown(self):
+        self.ctx.__exit__(None, None, None)
+
     def test_prerelease(self):
         version = StrictVersion('1.2.3a1')
         self.assertEqual(version.version, (1, 2, 3))
@@ -81,7 +89,7 @@ class VersionTestCase(unittest.TestCase):
                           (v1, v2, res))
 
 def test_suite():
-    return unittest.makeSuite(VersionTestCase)
+    return unittest.TestLoader().loadTestsFromTestCase(VersionTestCase)
 
 if __name__ == "__main__":
     run_unittest(test_suite())
diff --git a/setuptools/_distutils/tests/unix_compat.py b/setuptools/_distutils/tests/unix_compat.py
new file mode 100644
index 00000000..b7718c26
--- /dev/null
+++ b/setuptools/_distutils/tests/unix_compat.py
@@ -0,0 +1,16 @@
+import sys
+import unittest
+
+try:
+    import grp
+    import pwd
+except ImportError:
+    grp = pwd = None
+
+
+UNIX_ID_SUPPORT = grp and pwd
+UID_0_SUPPORT = UNIX_ID_SUPPORT and sys.platform != "cygwin"
+
+require_unix_id = unittest.skipUnless(
+    UNIX_ID_SUPPORT, "Requires grp and pwd support")
+require_uid_0 = unittest.skipUnless(UID_0_SUPPORT, "Requires UID 0 support")
diff --git a/setuptools/_distutils/unixccompiler.py b/setuptools/_distutils/unixccompiler.py
index a07e5988..715408f5 100644
--- a/setuptools/_distutils/unixccompiler.py
+++ b/setuptools/_distutils/unixccompiler.py
@@ -22,9 +22,7 @@ from distutils.ccompiler import \
 from distutils.errors import \
      DistutilsExecError, CompileError, LibError, LinkError
 from distutils import log
-
-if sys.platform == 'darwin':
-    import _osx_support
+from ._macos_compat import compiler_fixup
 
 # XXX Things not currently handled:
 #   * optimization/debug/warning flags; we just use whatever's in Python's
@@ -42,6 +40,66 @@ if sys.platform == 'darwin':
 #     options and carry on.
 
 
+def _split_env(cmd):
+    """
+    For macOS, split command into 'env' portion (if any)
+    and the rest of the linker command.
+
+    >>> _split_env(['a', 'b', 'c'])
+    ([], ['a', 'b', 'c'])
+    >>> _split_env(['/usr/bin/env', 'A=3', 'gcc'])
+    (['/usr/bin/env', 'A=3'], ['gcc'])
+    """
+    pivot = 0
+    if os.path.basename(cmd[0]) == "env":
+        pivot = 1
+        while '=' in cmd[pivot]:
+            pivot += 1
+    return cmd[:pivot], cmd[pivot:]
+
+
+def _split_aix(cmd):
+    """
+    AIX platforms prefix the compiler with the ld_so_aix
+    script, so split that from the linker command.
+
+    >>> _split_aix(['a', 'b', 'c'])
+    ([], ['a', 'b', 'c'])
+    >>> _split_aix(['/bin/foo/ld_so_aix', 'gcc'])
+    (['/bin/foo/ld_so_aix'], ['gcc'])
+    """
+    pivot = os.path.basename(cmd[0]) == 'ld_so_aix'
+    return cmd[:pivot], cmd[pivot:]
+
+
+def _linker_params(linker_cmd, compiler_cmd):
+    """
+    The linker command usually begins with the compiler
+    command (possibly multiple elements), followed by zero or more
+    params for shared library building.
+
+    If the LDSHARED env variable overrides the linker command,
+    however, the commands may not match.
+
+    Return the best guess of the linker parameters by stripping
+    the linker command. If the compiler command does not
+    match the linker command, assume the linker command is
+    just the first element.
+
+    >>> _linker_params('gcc foo bar'.split(), ['gcc'])
+    ['foo', 'bar']
+    >>> _linker_params('gcc foo bar'.split(), ['other'])
+    ['foo', 'bar']
+    >>> _linker_params('ccache gcc foo bar'.split(), 'ccache gcc'.split())
+    ['foo', 'bar']
+    >>> _linker_params(['gcc'], ['gcc'])
+    []
+    """
+    c_len = len(compiler_cmd)
+    pivot = c_len if linker_cmd[:c_len] == compiler_cmd else 1
+    return linker_cmd[pivot:]
+
+
 class UnixCCompiler(CCompiler):
 
     compiler_type = 'unix'
@@ -109,10 +167,8 @@ class UnixCCompiler(CCompiler):
                 raise CompileError(msg)
 
     def _compile(self, obj, src, ext, cc_args, extra_postargs, pp_opts):
-        compiler_so = self.compiler_so
-        if sys.platform == 'darwin':
-            compiler_so = _osx_support.compiler_fixup(compiler_so,
-                                                    cc_args + extra_postargs)
+        compiler_so = compiler_fixup(
+            self.compiler_so, cc_args + extra_postargs)
         try:
             self.spawn(compiler_so + cc_args + [src, '-o', obj] +
                        extra_postargs)
@@ -173,33 +229,22 @@ class UnixCCompiler(CCompiler):
                 ld_args.extend(extra_postargs)
             self.mkpath(os.path.dirname(output_filename))
             try:
-                if target_desc == CCompiler.EXECUTABLE:
-                    linker = self.linker_exe[:]
-                else:
-                    linker = self.linker_so[:]
+                # Select a linker based on context: linker_exe when
+                # building an executable or linker_so (with shared options)
+                # when building a shared library.
+                building_exe = target_desc == CCompiler.EXECUTABLE
+                linker = (self.linker_exe if building_exe else self.linker_so)[:]
+
                 if target_lang == "c++" and self.compiler_cxx:
-                    # skip over environment variable settings if /usr/bin/env
-                    # is used to set up the linker's environment.
-                    # This is needed on OSX. Note: this assumes that the
-                    # normal and C++ compiler have the same environment
-                    # settings.
-                    i = 0
-                    if os.path.basename(linker[0]) == "env":
-                        i = 1
-                        while '=' in linker[i]:
-                            i += 1
-
-                    if os.path.basename(linker[i]) == 'ld_so_aix':
-                        # AIX platforms prefix the compiler with the ld_so_aix
-                        # script, so we need to adjust our linker index
-                        offset = 1
-                    else:
-                        offset = 0
-
-                    linker[i+offset] = self.compiler_cxx[i]
-
-                if sys.platform == 'darwin':
-                    linker = _osx_support.compiler_fixup(linker, ld_args)
+                    env, linker_ne = _split_env(linker)
+                    aix, linker_na = _split_aix(linker_ne)
+                    _, compiler_cxx_ne = _split_env(self.compiler_cxx)
+                    _, linker_exe_ne = _split_env(self.linker_exe)
+
+                    params = _linker_params(linker_na, linker_exe_ne)
+                    linker = env + aix + compiler_cxx_ne + params
+
+                linker = compiler_fixup(linker, ld_args)
 
                 self.spawn(linker + ld_args)
             except DistutilsExecError as msg:
diff --git a/setuptools/_distutils/util.py b/setuptools/_distutils/util.py
index ac6d446d..6d506d7e 100644
--- a/setuptools/_distutils/util.py
+++ b/setuptools/_distutils/util.py
@@ -9,6 +9,7 @@ import re
 import importlib.util
 import string
 import sys
+import sysconfig
 from distutils.errors import DistutilsPlatformError
 from distutils.dep_util import newer
 from distutils.spawn import spawn
@@ -20,82 +21,29 @@ from .py35compat import _optim_args_from_interpreter_flags
 def get_host_platform():
     """Return a string that identifies the current platform.  This is used mainly to
     distinguish platform-specific build directories and platform-specific built
-    distributions.  Typically includes the OS name and version and the
-    architecture (as supplied by 'os.uname()'), although the exact information
-    included depends on the OS; eg. on Linux, the kernel version isn't
-    particularly important.
-
-    Examples of returned values:
-       linux-i586
-       linux-alpha (?)
-       solaris-2.6-sun4u
-
-    Windows will return one of:
-       win-amd64 (64bit Windows on AMD64 (aka x86_64, Intel64, EM64T, etc)
-       win32 (all others - specifically, sys.platform is returned)
-
-    For other non-POSIX platforms, currently just returns 'sys.platform'.
-
+    distributions.
     """
-    if os.name == 'nt':
-        if 'amd64' in sys.version.lower():
-            return 'win-amd64'
-        if '(arm)' in sys.version.lower():
-            return 'win-arm32'
-        if '(arm64)' in sys.version.lower():
-            return 'win-arm64'
-        return sys.platform
-
-    # Set for cross builds explicitly
-    if "_PYTHON_HOST_PLATFORM" in os.environ:
-        return os.environ["_PYTHON_HOST_PLATFORM"]
-
-    if os.name != "posix" or not hasattr(os, 'uname'):
-        # XXX what about the architecture? NT is Intel or Alpha,
-        # Mac OS is M68k or PPC, etc.
-        return sys.platform
-
-    # Try to distinguish various flavours of Unix
-
-    (osname, host, release, version, machine) = os.uname()
-
-    # Convert the OS name to lowercase, remove '/' characters, and translate
-    # spaces (for "Power Macintosh")
-    osname = osname.lower().replace('/', '')
-    machine = machine.replace(' ', '_')
-    machine = machine.replace('/', '-')
-
-    if osname[:5] == "linux":
-        # At least on Linux/Intel, 'machine' is the processor --
-        # i386, etc.
-        # XXX what about Alpha, SPARC, etc?
-        return  "%s-%s" % (osname, machine)
-    elif osname[:5] == "sunos":
-        if release[0] >= "5":           # SunOS 5 == Solaris 2
-            osname = "solaris"
-            release = "%d.%s" % (int(release[0]) - 3, release[2:])
-            # We can't use "platform.architecture()[0]" because a
-            # bootstrap problem. We use a dict to get an error
-            # if some suspicious happens.
-            bitness = {2147483647:"32bit", 9223372036854775807:"64bit"}
-            machine += ".%s" % bitness[sys.maxsize]
-        # fall through to standard osname-release-machine representation
-    elif osname[:3] == "aix":
-        from .py38compat import aix_platform
-        return aix_platform(osname, version, release)
-    elif osname[:6] == "cygwin":
-        osname = "cygwin"
-        rel_re = re.compile (r'[\d.]+', re.ASCII)
-        m = rel_re.match(release)
-        if m:
-            release = m.group()
-    elif osname[:6] == "darwin":
-        import _osx_support, distutils.sysconfig
-        osname, release, machine = _osx_support.get_platform_osx(
-                                        distutils.sysconfig.get_config_vars(),
-                                        osname, release, machine)
-
-    return "%s-%s-%s" % (osname, release, machine)
+
+    # We initially exposed platforms as defined in Python 3.9
+    # even with older Python versions when distutils was split out.
+    # Now that we delegate to stdlib sysconfig we need to restore this
+    # in case anyone has started to depend on it.
+
+    if sys.version_info < (3, 8):
+        if os.name == 'nt':
+            if '(arm)' in sys.version.lower():
+                return 'win-arm32'
+            if '(arm64)' in sys.version.lower():
+                return 'win-arm64'
+
+    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 .py38compat import aix_platform
+                return aix_platform(osname, version, release)
+
+    return sysconfig.get_platform()
 
 def get_platform():
     if os.name == 'nt':
diff --git a/setuptools/_distutils/version.py b/setuptools/_distutils/version.py
index c33bebae..31f504e4 100644
--- a/setuptools/_distutils/version.py
+++ b/setuptools/_distutils/version.py
@@ -27,6 +27,20 @@ Every version number class implements the following interface:
 """
 
 import re
+import warnings
+import contextlib
+
+
+@contextlib.contextmanager
+def suppress_known_deprecation():
+    with warnings.catch_warnings(record=True) as ctx:
+        warnings.filterwarnings(
+            action='default',
+            category=DeprecationWarning,
+            message="distutils Version classes are deprecated.",
+        )
+        yield ctx
+
 
 class Version:
     """Abstract base class for version numbering classes.  Just provides
@@ -38,6 +52,12 @@ class Version:
     def __init__ (self, vstring=None):
         if vstring:
             self.parse(vstring)
+        warnings.warn(
+            "distutils Version classes are deprecated. "
+            "Use packaging.version instead.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
 
     def __repr__ (self):
         return "%s ('%s')" % (self.__class__.__name__, str(self))
@@ -165,7 +185,8 @@ class StrictVersion (Version):
 
     def _cmp (self, other):
         if isinstance(other, str):
-            other = StrictVersion(other)
+            with suppress_known_deprecation():
+                other = StrictVersion(other)
         elif not isinstance(other, StrictVersion):
             return NotImplemented
 
@@ -301,11 +322,6 @@ class LooseVersion (Version):
 
     component_re = re.compile(r'(\d+ | [a-z]+ | \.)', re.VERBOSE)
 
-    def __init__ (self, vstring=None):
-        if vstring:
-            self.parse(vstring)
-
-
     def parse (self, vstring):
         # I've given up on thinking I can reconstruct the version string
         # from the parsed tuple -- so I just store the string here for
diff --git a/setuptools/_distutils/versionpredicate.py b/setuptools/_distutils/versionpredicate.py
index 062c98f2..55f25d91 100644
--- a/setuptools/_distutils/versionpredicate.py
+++ b/setuptools/_distutils/versionpredicate.py
@@ -23,7 +23,9 @@ def splitUp(pred):
     if not res:
         raise ValueError("bad package restriction syntax: %r" % pred)
     comp, verStr = res.groups()
-    return (comp, distutils.version.StrictVersion(verStr))
+    with distutils.version.suppress_known_deprecation():
+        other = distutils.version.StrictVersion(verStr)
+    return (comp, other)
 
 compmap = {"<": operator.lt, "<=": operator.le, "==": operator.eq,
            ">": operator.gt, ">=": operator.ge, "!=": operator.ne}
@@ -162,5 +164,6 @@ def split_provision(value):
         raise ValueError("illegal provides specification: %r" % value)
     ver = m.group(2) or None
     if ver:
-        ver = distutils.version.StrictVersion(ver)
+        with distutils.version.suppress_known_deprecation():
+            ver = distutils.version.StrictVersion(ver)
     return m.group(1), ver