GH-103480: make sysconfig a package (GH-110785)

2 files changed, 902 insertions, 0 deletions

diff --git a/Lib/sysconfig/__init__.py b/Lib/sysconfig/__init__.py
new file mode 100644
index 0000000..68d30c0
--- /dev/null
+++ b/Lib/sysconfig/__init__.py
@@ -0,0 +1,657 @@
+"""Access to Python's configuration information."""
+
+import os
+import sys
+import threading
+from os.path import realpath
+
+__all__ = [
+    'get_config_h_filename',
+    'get_config_var',
+    'get_config_vars',
+    'get_makefile_filename',
+    'get_path',
+    'get_path_names',
+    'get_paths',
+    'get_platform',
+    'get_python_version',
+    'get_scheme_names',
+    'parse_config_h',
+]
+
+# Keys for get_config_var() that are never converted to Python integers.
+_ALWAYS_STR = {
+    'MACOSX_DEPLOYMENT_TARGET',
+}
+
+_INSTALL_SCHEMES = {
+    'posix_prefix': {
+        'stdlib': '{installed_base}/{platlibdir}/python{py_version_short}',
+        'platstdlib': '{platbase}/{platlibdir}/python{py_version_short}',
+        'purelib': '{base}/lib/python{py_version_short}/site-packages',
+        'platlib': '{platbase}/{platlibdir}/python{py_version_short}/site-packages',
+        'include':
+            '{installed_base}/include/python{py_version_short}{abiflags}',
+        'platinclude':
+            '{installed_platbase}/include/python{py_version_short}{abiflags}',
+        'scripts': '{base}/bin',
+        'data': '{base}',
+        },
+    'posix_home': {
+        'stdlib': '{installed_base}/lib/python',
+        'platstdlib': '{base}/lib/python',
+        'purelib': '{base}/lib/python',
+        'platlib': '{base}/lib/python',
+        'include': '{installed_base}/include/python',
+        'platinclude': '{installed_base}/include/python',
+        'scripts': '{base}/bin',
+        'data': '{base}',
+        },
+    'nt': {
+        'stdlib': '{installed_base}/Lib',
+        'platstdlib': '{base}/Lib',
+        'purelib': '{base}/Lib/site-packages',
+        'platlib': '{base}/Lib/site-packages',
+        'include': '{installed_base}/Include',
+        'platinclude': '{installed_base}/Include',
+        'scripts': '{base}/Scripts',
+        'data': '{base}',
+        },
+    # Downstream distributors can overwrite the default install scheme.
+    # This is done to support downstream modifications where distributors change
+    # the installation layout (eg. different site-packages directory).
+    # So, distributors will change the default scheme to one that correctly
+    # represents their layout.
+    # This presents an issue for projects/people that need to bootstrap virtual
+    # environments, like virtualenv. As distributors might now be customizing
+    # the default install scheme, there is no guarantee that the information
+    # returned by sysconfig.get_default_scheme/get_paths is correct for
+    # a virtual environment, the only guarantee we have is that it is correct
+    # for the *current* environment. When bootstrapping a virtual environment,
+    # we need to know its layout, so that we can place the files in the
+    # correct locations.
+    # The "*_venv" install scheme is a scheme to bootstrap virtual environments,
+    # essentially identical to the default posix_prefix/nt schemes.
+    # Downstream distributors who patch posix_prefix/nt scheme are encouraged to
+    # leave the following schemes unchanged
+    'posix_venv': {
+        'stdlib': '{installed_base}/{platlibdir}/python{py_version_short}',
+        'platstdlib': '{platbase}/{platlibdir}/python{py_version_short}',
+        'purelib': '{base}/lib/python{py_version_short}/site-packages',
+        'platlib': '{platbase}/{platlibdir}/python{py_version_short}/site-packages',
+        'include':
+            '{installed_base}/include/python{py_version_short}{abiflags}',
+        'platinclude':
+            '{installed_platbase}/include/python{py_version_short}{abiflags}',
+        'scripts': '{base}/bin',
+        'data': '{base}',
+        },
+    'nt_venv': {
+        'stdlib': '{installed_base}/Lib',
+        'platstdlib': '{base}/Lib',
+        'purelib': '{base}/Lib/site-packages',
+        'platlib': '{base}/Lib/site-packages',
+        'include': '{installed_base}/Include',
+        'platinclude': '{installed_base}/Include',
+        'scripts': '{base}/Scripts',
+        'data': '{base}',
+        },
+    }
+
+# For the OS-native venv scheme, we essentially provide an alias:
+if os.name == 'nt':
+    _INSTALL_SCHEMES['venv'] = _INSTALL_SCHEMES['nt_venv']
+else:
+    _INSTALL_SCHEMES['venv'] = _INSTALL_SCHEMES['posix_venv']
+
+
+# NOTE: site.py has copy of this function.
+# Sync it when modify this function.
+def _getuserbase():
+    env_base = os.environ.get("PYTHONUSERBASE", None)
+    if env_base:
+        return env_base
+
+    # Emscripten, VxWorks, and WASI have no home directories
+    if sys.platform in {"emscripten", "vxworks", "wasi"}:
+        return None
+
+    def joinuser(*args):
+        return os.path.expanduser(os.path.join(*args))
+
+    if os.name == "nt":
+        base = os.environ.get("APPDATA") or "~"
+        return joinuser(base, "Python")
+
+    if sys.platform == "darwin" and sys._framework:
+        return joinuser("~", "Library", sys._framework,
+                        f"{sys.version_info[0]}.{sys.version_info[1]}")
+
+    return joinuser("~", ".local")
+
+_HAS_USER_BASE = (_getuserbase() is not None)
+
+if _HAS_USER_BASE:
+    _INSTALL_SCHEMES |= {
+        # NOTE: When modifying "purelib" scheme, update site._get_path() too.
+        'nt_user': {
+            'stdlib': '{userbase}/Python{py_version_nodot_plat}',
+            'platstdlib': '{userbase}/Python{py_version_nodot_plat}',
+            'purelib': '{userbase}/Python{py_version_nodot_plat}/site-packages',
+            'platlib': '{userbase}/Python{py_version_nodot_plat}/site-packages',
+            'include': '{userbase}/Python{py_version_nodot_plat}/Include',
+            'scripts': '{userbase}/Python{py_version_nodot_plat}/Scripts',
+            'data': '{userbase}',
+            },
+        'posix_user': {
+            'stdlib': '{userbase}/{platlibdir}/python{py_version_short}',
+            'platstdlib': '{userbase}/{platlibdir}/python{py_version_short}',
+            'purelib': '{userbase}/lib/python{py_version_short}/site-packages',
+            'platlib': '{userbase}/lib/python{py_version_short}/site-packages',
+            'include': '{userbase}/include/python{py_version_short}',
+            'scripts': '{userbase}/bin',
+            'data': '{userbase}',
+            },
+        'osx_framework_user': {
+            'stdlib': '{userbase}/lib/python',
+            'platstdlib': '{userbase}/lib/python',
+            'purelib': '{userbase}/lib/python/site-packages',
+            'platlib': '{userbase}/lib/python/site-packages',
+            'include': '{userbase}/include/python{py_version_short}',
+            'scripts': '{userbase}/bin',
+            'data': '{userbase}',
+            },
+    }
+
+_SCHEME_KEYS = ('stdlib', 'platstdlib', 'purelib', 'platlib', 'include',
+                'scripts', 'data')
+
+_PY_VERSION = sys.version.split()[0]
+_PY_VERSION_SHORT = f'{sys.version_info[0]}.{sys.version_info[1]}'
+_PY_VERSION_SHORT_NO_DOT = f'{sys.version_info[0]}{sys.version_info[1]}'
+_PREFIX = os.path.normpath(sys.prefix)
+_BASE_PREFIX = os.path.normpath(sys.base_prefix)
+_EXEC_PREFIX = os.path.normpath(sys.exec_prefix)
+_BASE_EXEC_PREFIX = os.path.normpath(sys.base_exec_prefix)
+# Mutex guarding initialization of _CONFIG_VARS.
+_CONFIG_VARS_LOCK = threading.RLock()
+_CONFIG_VARS = None
+# True iff _CONFIG_VARS has been fully initialized.
+_CONFIG_VARS_INITIALIZED = False
+_USER_BASE = None
+
+
+def _safe_realpath(path):
+    try:
+        return realpath(path)
+    except OSError:
+        return path
+
+if sys.executable:
+    _PROJECT_BASE = os.path.dirname(_safe_realpath(sys.executable))
+else:
+    # sys.executable can be empty if argv[0] has been changed and Python is
+    # unable to retrieve the real program name
+    _PROJECT_BASE = _safe_realpath(os.getcwd())
+
+# In a virtual environment, `sys._home` gives us the target directory
+# `_PROJECT_BASE` for the executable that created it when the virtual
+# python is an actual executable ('venv --copies' or Windows).
+_sys_home = getattr(sys, '_home', None)
+if _sys_home:
+    _PROJECT_BASE = _sys_home
+
+if os.name == 'nt':
+    # In a source build, the executable is in a subdirectory of the root
+    # that we want (<root>\PCbuild\<platname>).
+    # `_BASE_PREFIX` is used as the base installation is where the source
+    # will be.  The realpath is needed to prevent mount point confusion
+    # that can occur with just string comparisons.
+    if _safe_realpath(_PROJECT_BASE).startswith(
+            _safe_realpath(f'{_BASE_PREFIX}\\PCbuild')):
+        _PROJECT_BASE = _BASE_PREFIX
+
+# set for cross builds
+if "_PYTHON_PROJECT_BASE" in os.environ:
+    _PROJECT_BASE = _safe_realpath(os.environ["_PYTHON_PROJECT_BASE"])
+
+def is_python_build(check_home=None):
+    if check_home is not None:
+        import warnings
+        warnings.warn("check_home argument is deprecated and ignored.",
+                      DeprecationWarning, stacklevel=2)
+    for fn in ("Setup", "Setup.local"):
+        if os.path.isfile(os.path.join(_PROJECT_BASE, "Modules", fn)):
+            return True
+    return False
+
+_PYTHON_BUILD = is_python_build()
+
+if _PYTHON_BUILD:
+    for scheme in ('posix_prefix', 'posix_home'):
+        # On POSIX-y platforms, Python will:
+        # - Build from .h files in 'headers' (which is only added to the
+        #   scheme when building CPython)
+        # - Install .h files to 'include'
+        scheme = _INSTALL_SCHEMES[scheme]
+        scheme['headers'] = scheme['include']
+        scheme['include'] = '{srcdir}/Include'
+        scheme['platinclude'] = '{projectbase}/.'
+    del scheme
+
+
+def _subst_vars(s, local_vars):
+    try:
+        return s.format(**local_vars)
+    except KeyError as var:
+        try:
+            return s.format(**os.environ)
+        except KeyError:
+            raise AttributeError(f'{var}') from None
+
+def _extend_dict(target_dict, other_dict):
+    target_keys = target_dict.keys()
+    for key, value in other_dict.items():
+        if key in target_keys:
+            continue
+        target_dict[key] = value
+
+
+def _expand_vars(scheme, vars):
+    res = {}
+    if vars is None:
+        vars = {}
+    _extend_dict(vars, get_config_vars())
+    if os.name == 'nt':
+        # On Windows we want to substitute 'lib' for schemes rather
+        # than the native value (without modifying vars, in case it
+        # was passed in)
+        vars = vars | {'platlibdir': 'lib'}
+
+    for key, value in _INSTALL_SCHEMES[scheme].items():
+        if os.name in ('posix', 'nt'):
+            value = os.path.expanduser(value)
+        res[key] = os.path.normpath(_subst_vars(value, vars))
+    return res
+
+
+def _get_preferred_schemes():
+    if os.name == 'nt':
+        return {
+            'prefix': 'nt',
+            'home': 'posix_home',
+            'user': 'nt_user',
+        }
+    if sys.platform == 'darwin' and sys._framework:
+        return {
+            'prefix': 'posix_prefix',
+            'home': 'posix_home',
+            'user': 'osx_framework_user',
+        }
+    return {
+        'prefix': 'posix_prefix',
+        'home': 'posix_home',
+        'user': 'posix_user',
+    }
+
+
+def get_preferred_scheme(key):
+    if key == 'prefix' and sys.prefix != sys.base_prefix:
+        return 'venv'
+    scheme = _get_preferred_schemes()[key]
+    if scheme not in _INSTALL_SCHEMES:
+        raise ValueError(
+            f"{key!r} returned {scheme!r}, which is not a valid scheme "
+            f"on this platform"
+        )
+    return scheme
+
+
+def get_default_scheme():
+    return get_preferred_scheme('prefix')
+
+
+def get_makefile_filename():
+    """Return the path of the Makefile."""
+    if _PYTHON_BUILD:
+        return os.path.join(_PROJECT_BASE, "Makefile")
+    if hasattr(sys, 'abiflags'):
+        config_dir_name = f'config-{_PY_VERSION_SHORT}{sys.abiflags}'
+    else:
+        config_dir_name = 'config'
+    if hasattr(sys.implementation, '_multiarch'):
+        config_dir_name += f'-{sys.implementation._multiarch}'
+    return os.path.join(get_path('stdlib'), config_dir_name, 'Makefile')
+
+
+def _get_sysconfigdata_name():
+    multiarch = getattr(sys.implementation, '_multiarch', '')
+    return os.environ.get(
+        '_PYTHON_SYSCONFIGDATA_NAME',
+        f'_sysconfigdata_{sys.abiflags}_{sys.platform}_{multiarch}',
+    )
+
+def _init_posix(vars):
+    """Initialize the module as appropriate for POSIX systems."""
+    # _sysconfigdata is generated at build time, see _generate_posix_vars()
+    name = _get_sysconfigdata_name()
+    _temp = __import__(name, globals(), locals(), ['build_time_vars'], 0)
+    build_time_vars = _temp.build_time_vars
+    vars.update(build_time_vars)
+
+def _init_non_posix(vars):
+    """Initialize the module as appropriate for NT"""
+    # set basic install directories
+    import _winapi
+    import _sysconfig
+    vars['LIBDEST'] = get_path('stdlib')
+    vars['BINLIBDEST'] = get_path('platstdlib')
+    vars['INCLUDEPY'] = get_path('include')
+
+    # Add EXT_SUFFIX, SOABI, and Py_NOGIL
+    vars.update(_sysconfig.config_vars())
+
+    vars['LIBDIR'] = _safe_realpath(os.path.join(get_config_var('installed_base'), 'libs'))
+    if hasattr(sys, 'dllhandle'):
+        dllhandle = _winapi.GetModuleFileName(sys.dllhandle)
+        vars['LIBRARY'] = os.path.basename(_safe_realpath(dllhandle))
+        vars['LDLIBRARY'] = vars['LIBRARY']
+    vars['EXE'] = '.exe'
+    vars['VERSION'] = _PY_VERSION_SHORT_NO_DOT
+    vars['BINDIR'] = os.path.dirname(_safe_realpath(sys.executable))
+    vars['TZPATH'] = ''
+
+#
+# public APIs
+#
+
+
+def parse_config_h(fp, vars=None):
+    """Parse a config.h-style file.
+
+    A dictionary containing name/value pairs is returned.  If an
+    optional dictionary is passed in as the second argument, it is
+    used instead of a new dictionary.
+    """
+    if vars is None:
+        vars = {}
+    import re
+    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:
+                if n in _ALWAYS_STR:
+                    raise ValueError
+                v = int(v)
+            except ValueError:
+                pass
+            vars[n] = v
+        else:
+            m = undef_rx.match(line)
+            if m:
+                vars[m.group(1)] = 0
+    return vars
+
+
+def get_config_h_filename():
+    """Return the path of pyconfig.h."""
+    if _PYTHON_BUILD:
+        if os.name == "nt":
+            inc_dir = os.path.join(_PROJECT_BASE, "PC")
+        else:
+            inc_dir = _PROJECT_BASE
+    else:
+        inc_dir = get_path('platinclude')
+    return os.path.join(inc_dir, 'pyconfig.h')
+
+
+def get_scheme_names():
+    """Return a tuple containing the schemes names."""
+    return tuple(sorted(_INSTALL_SCHEMES))
+
+
+def get_path_names():
+    """Return a tuple containing the paths names."""
+    return _SCHEME_KEYS
+
+
+def get_paths(scheme=get_default_scheme(), vars=None, expand=True):
+    """Return a mapping containing an install scheme.
+
+    ``scheme`` is the install scheme name. If not provided, it will
+    return the default scheme for the current platform.
+    """
+    if expand:
+        return _expand_vars(scheme, vars)
+    else:
+        return _INSTALL_SCHEMES[scheme]
+
+
+def get_path(name, scheme=get_default_scheme(), vars=None, expand=True):
+    """Return a path corresponding to the scheme.
+
+    ``scheme`` is the install scheme name.
+    """
+    return get_paths(scheme, vars, expand)[name]
+
+
+def _init_config_vars():
+    global _CONFIG_VARS
+    _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
+    _CONFIG_VARS['py_version'] = _PY_VERSION
+    _CONFIG_VARS['py_version_short'] = _PY_VERSION_SHORT
+    _CONFIG_VARS['py_version_nodot'] = _PY_VERSION_SHORT_NO_DOT
+    _CONFIG_VARS['installed_base'] = _BASE_PREFIX
+    _CONFIG_VARS['base'] = _PREFIX
+    _CONFIG_VARS['installed_platbase'] = _BASE_EXEC_PREFIX
+    _CONFIG_VARS['platbase'] = _EXEC_PREFIX
+    _CONFIG_VARS['projectbase'] = _PROJECT_BASE
+    _CONFIG_VARS['platlibdir'] = sys.platlibdir
+    try:
+        _CONFIG_VARS['abiflags'] = sys.abiflags
+    except AttributeError:
+        # sys.abiflags may not be defined on all platforms.
+        _CONFIG_VARS['abiflags'] = ''
+    try:
+        _CONFIG_VARS['py_version_nodot_plat'] = sys.winver.replace('.', '')
+    except AttributeError:
+        _CONFIG_VARS['py_version_nodot_plat'] = ''
+
+    if os.name == 'nt':
+        _init_non_posix(_CONFIG_VARS)
+        _CONFIG_VARS['VPATH'] = sys._vpath
+    if os.name == 'posix':
+        _init_posix(_CONFIG_VARS)
+    if _HAS_USER_BASE:
+        # Setting 'userbase' is done below the call to the
+        # init function to enable using 'get_config_var' in
+        # the init-function.
+        _CONFIG_VARS['userbase'] = _getuserbase()
+
+    # 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'] = _safe_realpath(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)
+
+    global _CONFIG_VARS_INITIALIZED
+    _CONFIG_VARS_INITIALIZED = True
+
+
+def get_config_vars(*args):
+    """With no arguments, return a dictionary of all configuration
+    variables relevant for the current platform.
+
+    On Unix, this means every variable defined in Python's installed Makefile;
+    On Windows it's a much smaller set.
+
+    With arguments, return a list of values that result from looking up
+    each argument in the configuration variable dictionary.
+    """
+
+    # Avoid claiming the lock once initialization is complete.
+    if not _CONFIG_VARS_INITIALIZED:
+        with _CONFIG_VARS_LOCK:
+            # Test again with the lock held to avoid races. Note that
+            # we test _CONFIG_VARS here, not _CONFIG_VARS_INITIALIZED,
+            # to ensure that recursive calls to get_config_vars()
+            # don't re-enter init_config_vars().
+            if _CONFIG_VARS is None:
+                _init_config_vars()
+
+    if args:
+        vals = []
+        for name in args:
+            vals.append(_CONFIG_VARS.get(name))
+        return vals
+    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 get_config_vars().get(name)
+    """
+    return get_config_vars().get(name)
+
+
+def get_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; 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'.
+
+    """
+    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
+
+    if os.name != "posix" or not hasattr(os, 'uname'):
+        # XXX what about the architecture? NT is Intel or Alpha
+        return sys.platform
+
+    # Set for cross builds explicitly
+    if "_PYTHON_HOST_PLATFORM" in os.environ:
+        return os.environ["_PYTHON_HOST_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  f"{osname}-{machine}"
+    elif osname[:5] == "sunos":
+        if release[0] >= "5":           # SunOS 5 == Solaris 2
+            osname = "solaris"
+            release = f"{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 += f".{bitness[sys.maxsize]}"
+        # fall through to standard osname-release-machine representation
+    elif osname[:3] == "aix":
+        from _aix_support import aix_platform
+        return aix_platform()
+    elif osname[:6] == "cygwin":
+        osname = "cygwin"
+        import re
+        rel_re = re.compile(r'[\d.]+')
+        m = rel_re.match(release)
+        if m:
+            release = m.group()
+    elif osname[:6] == "darwin":
+        import _osx_support
+        osname, release, machine = _osx_support.get_platform_osx(
+                                            get_config_vars(),
+                                            osname, release, machine)
+
+    return f"{osname}-{release}-{machine}"
+
+
+def get_python_version():
+    return _PY_VERSION_SHORT
+
+
+def expand_makefile_vars(s, vars):
+    """Expand Makefile-style variables -- "${foo}" or "$(foo)" -- in
+    'string' according to 'vars' (a dictionary mapping variable names to
+    values).  Variables not present in 'vars' are silently expanded to the
+    empty string.  The variable values in 'vars' should not contain further
+    variable expansions; if 'vars' is the output of 'parse_makefile()',
+    you're fine.  Returns a variable-expanded version of 's'.
+    """
+    import re
+
+    # This algorithm does multiple expansion, so if vars['foo'] contains
+    # "${bar}", it will expand ${foo} to ${bar}, and then expand
+    # ${bar}... and so forth.  This is fine as long as 'vars' comes from
+    # 'parse_makefile()', which takes care of such expansions eagerly,
+    # according to make's variable expansion semantics.
+
+    while True:
+        m = re.search(_findvar1_rx, s) or re.search(_findvar2_rx, s)
+        if m:
+            (beg, end) = m.span()
+            s = s[0:beg] + vars.get(m.group(1)) + s[end:]
+        else:
+            break
+    return s
diff --git a/Lib/sysconfig/__main__.py b/Lib/sysconfig/__main__.py
new file mode 100644
index 0000000..e0c3756
--- /dev/null
+++ b/Lib/sysconfig/__main__.py
@@ -0,0 +1,245 @@
+import os
+import sys
+from sysconfig import (
+    _ALWAYS_STR,
+    _PYTHON_BUILD,
+    _get_sysconfigdata_name,
+    get_config_h_filename,
+    get_config_vars,
+    get_default_scheme,
+    get_makefile_filename,
+    get_paths,
+    get_platform,
+    get_python_version,
+    parse_config_h,
+)
+
+
+# Regexes needed for parsing Makefile (and similar syntaxes,
+# like old-style Setup files).
+_variable_rx = r"([a-zA-Z][a-zA-Z0-9_]+)\s*=\s*(.*)"
+_findvar1_rx = r"\$\(([A-Za-z][A-Za-z0-9_]*)\)"
+_findvar2_rx = r"\${([A-Za-z][A-Za-z0-9_]*)}"
+
+
+def _parse_makefile(filename, vars=None, keep_unresolved=True):
+    """Parse a Makefile-style file.
+
+    A dictionary containing name/value pairs is returned.  If an
+    optional dictionary is passed in as the second argument, it is
+    used instead of a new dictionary.
+    """
+    import re
+
+    if vars is None:
+        vars = {}
+    done = {}
+    notdone = {}
+
+    with open(filename, encoding=sys.getfilesystemencoding(),
+              errors="surrogateescape") as f:
+        lines = f.readlines()
+
+    for line in lines:
+        if line.startswith('#') or line.strip() == '':
+            continue
+        m = re.match(_variable_rx, line)
+        if m:
+            n, v = m.group(1, 2)
+            v = v.strip()
+            # `$$' is a literal `$' in make
+            tmpv = v.replace('$$', '')
+
+            if "$" in tmpv:
+                notdone[n] = v
+            else:
+                try:
+                    if n in _ALWAYS_STR:
+                        raise ValueError
+
+                    v = int(v)
+                except ValueError:
+                    # insert literal `$'
+                    done[n] = v.replace('$$', '$')
+                else:
+                    done[n] = v
+
+    # do variable interpolation here
+    variables = list(notdone.keys())
+
+    # Variables with a 'PY_' prefix in the makefile. These need to
+    # be made available without that prefix through sysconfig.
+    # Special care is needed to ensure that variable expansion works, even
+    # if the expansion uses the name without a prefix.
+    renamed_variables = ('CFLAGS', 'LDFLAGS', 'CPPFLAGS')
+
+    while len(variables) > 0:
+        for name in tuple(variables):
+            value = notdone[name]
+            m1 = re.search(_findvar1_rx, value)
+            m2 = re.search(_findvar2_rx, value)
+            if m1 and m2:
+                m = m1 if m1.start() < m2.start() else m2
+            else:
+                m = m1 if m1 else m2
+            if m is not None:
+                n = m.group(1)
+                found = True
+                if n in done:
+                    item = str(done[n])
+                elif n in notdone:
+                    # get it on a subsequent round
+                    found = False
+                elif n in os.environ:
+                    # do it like make: fall back to environment
+                    item = os.environ[n]
+
+                elif n in renamed_variables:
+                    if (name.startswith('PY_') and
+                        name[3:] in renamed_variables):
+                        item = ""
+
+                    elif 'PY_' + n in notdone:
+                        found = False
+
+                    else:
+                        item = str(done['PY_' + n])
+
+                else:
+                    done[n] = item = ""
+
+                if found:
+                    after = value[m.end():]
+                    value = value[:m.start()] + item + after
+                    if "$" in after:
+                        notdone[name] = value
+                    else:
+                        try:
+                            if name in _ALWAYS_STR:
+                                raise ValueError
+                            value = int(value)
+                        except ValueError:
+                            done[name] = value.strip()
+                        else:
+                            done[name] = value
+                        variables.remove(name)
+
+                        if name.startswith('PY_') \
+                        and name[3:] in renamed_variables:
+
+                            name = name[3:]
+                            if name not in done:
+                                done[name] = value
+
+            else:
+                # Adds unresolved variables to the done dict.
+                # This is disabled when called from distutils.sysconfig
+                if keep_unresolved:
+                    done[name] = value
+                # bogus variable reference (e.g. "prefix=$/opt/python");
+                # just drop it since we can't deal
+                variables.remove(name)
+
+    # strip spurious spaces
+    for k, v in done.items():
+        if isinstance(v, str):
+            done[k] = v.strip()
+
+    # save the results in the global dictionary
+    vars.update(done)
+    return vars
+
+
+def _print_config_dict(d, stream):
+    print ("{", file=stream)
+    for k, v in sorted(d.items()):
+        print(f"    {k!r}: {v!r},", file=stream)
+    print ("}", file=stream)
+
+
+def _generate_posix_vars():
+    """Generate the Python module containing build-time variables."""
+    vars = {}
+    # load the installed Makefile:
+    makefile = get_makefile_filename()
+    try:
+        _parse_makefile(makefile, vars)
+    except OSError as e:
+        msg = f"invalid Python installation: unable to open {makefile}"
+        if hasattr(e, "strerror"):
+            msg = f"{msg} ({e.strerror})"
+        raise OSError(msg)
+    # load the installed pyconfig.h:
+    config_h = get_config_h_filename()
+    try:
+        with open(config_h, encoding="utf-8") as f:
+            parse_config_h(f, vars)
+    except OSError as e:
+        msg = f"invalid Python installation: unable to open {config_h}"
+        if hasattr(e, "strerror"):
+            msg = f"{msg} ({e.strerror})"
+        raise OSError(msg)
+    # On AIX, there are wrong paths to the linker scripts in the Makefile
+    # -- these paths are relative to the Python source, but when installed
+    # the scripts are in another directory.
+    if _PYTHON_BUILD:
+        vars['BLDSHARED'] = vars['LDSHARED']
+
+    # There's a chicken-and-egg situation on OS X with regards to the
+    # _sysconfigdata module after the changes introduced by #15298:
+    # get_config_vars() is called by get_platform() as part of the
+    # `make pybuilddir.txt` target -- which is a precursor to the
+    # _sysconfigdata.py module being constructed.  Unfortunately,
+    # get_config_vars() eventually calls _init_posix(), which attempts
+    # to import _sysconfigdata, which we won't have built yet.  In order
+    # for _init_posix() to work, if we're on Darwin, just mock up the
+    # _sysconfigdata module manually and populate it with the build vars.
+    # This is more than sufficient for ensuring the subsequent call to
+    # get_platform() succeeds.
+    name = _get_sysconfigdata_name()
+    if 'darwin' in sys.platform:
+        import types
+        module = types.ModuleType(name)
+        module.build_time_vars = vars
+        sys.modules[name] = module
+
+    pybuilddir = f'build/lib.{get_platform()}-{get_python_version()}'
+    if hasattr(sys, "gettotalrefcount"):
+        pybuilddir += '-pydebug'
+    os.makedirs(pybuilddir, exist_ok=True)
+    destfile = os.path.join(pybuilddir, name + '.py')
+
+    with open(destfile, 'w', encoding='utf8') as f:
+        f.write('# system configuration generated and used by'
+                ' the sysconfig module\n')
+        f.write('build_time_vars = ')
+        _print_config_dict(vars, stream=f)
+
+    # Create file used for sys.path fixup -- see Modules/getpath.c
+    with open('pybuilddir.txt', 'w', encoding='utf8') as f:
+        f.write(pybuilddir)
+
+
+def _print_dict(title, data):
+    for index, (key, value) in enumerate(sorted(data.items())):
+        if index == 0:
+            print(f'{title}: ')
+        print(f'\t{key} = "{value}"')
+
+
+def _main():
+    """Display all information sysconfig detains."""
+    if '--generate-posix-vars' in sys.argv:
+        _generate_posix_vars()
+        return
+    print(f'Platform: "{get_platform()}"')
+    print(f'Python version: "{get_python_version()}"')
+    print(f'Current installation scheme: "{get_default_scheme()}"')
+    print()
+    _print_dict('Paths', get_paths())
+    print()
+    _print_dict('Variables', get_config_vars())
+
+
+if __name__ == '__main__':
+    _main()