Vendored the packaging.tags module (#365)

See the commentary on https://github.com/pypa/wheel/pull/346 for the reason.

7 files changed, 806 insertions, 2 deletions

diff --git a/docs/news.rst b/docs/news.rst
index 14c69d9..cc15559 100644
--- a/docs/news.rst
+++ b/docs/news.rst
@@ -3,6 +3,8 @@ Release Notes
 
 **UNRELEASED**
 
+- Replaced install dependency on ``packaging`` with a vendored copy of its
+  ``tags`` module
 - Fixed ``bdist_wheel`` not working on FreeBSD due to mismatching platform tag
   name (it was not being converted to lowercase)
 
diff --git a/setup.cfg b/setup.cfg
index c6e4e7a..1d71854 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -34,7 +34,6 @@ package_dir=
 packages = find:
 python_requires = >=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*
 setup_requires = setuptools >= 40.9.0
-install_requires = packaging >= 20.2
 zip_safe = False
 
 [options.packages.find]
diff --git a/src/wheel/bdist_wheel.py b/src/wheel/bdist_wheel.py
index c9730f4..5dee1b7 100644
--- a/src/wheel/bdist_wheel.py
+++ b/src/wheel/bdist_wheel.py
@@ -20,12 +20,12 @@ from shutil import rmtree
 from sysconfig import get_config_var
 from zipfile import ZIP_DEFLATED, ZIP_STORED
 
-from packaging import tags
 import pkg_resources
 
 from .pkginfo import write_pkg_info
 from .macosx_libfile import calculate_macosx_platform_tag
 from .metadata import pkginfo_to_metadata
+from .vendored.packaging import tags
 from .wheelfile import WheelFile
 from . import __version__ as wheel_version
 
diff --git a/src/wheel/vendored/__init__.py b/src/wheel/vendored/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/src/wheel/vendored/__init__.py
diff --git a/src/wheel/vendored/packaging/__init__.py b/src/wheel/vendored/packaging/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/src/wheel/vendored/packaging/__init__.py
diff --git a/src/wheel/vendored/packaging/_typing.py b/src/wheel/vendored/packaging/_typing.py
new file mode 100644
index 0000000..e308e10
--- /dev/null
+++ b/src/wheel/vendored/packaging/_typing.py
@@ -0,0 +1,50 @@
+# Vendored from packaging v20.4.
+
+"""For neatly implementing static typing in packaging.
+
+`mypy` - the static type analysis tool we use - uses the `typing` module, which
+provides core functionality fundamental to mypy's functioning.
+
+Generally, `typing` would be imported at runtime and used in that fashion -
+it acts as a no-op at runtime and does not have any run-time overhead by
+design.
+
+As it turns out, `typing` is not vendorable - it uses separate sources for
+Python 2/Python 3. Thus, this codebase can not expect it to be present.
+To work around this, mypy allows the typing import to be behind a False-y
+optional to prevent it from running at runtime and type-comments can be used
+to remove the need for the types to be accessible directly during runtime.
+
+This module provides the False-y guard in a nicely named fashion so that a
+curious maintainer can reach here to read this.
+
+In packaging, all static-typing related imports should be guarded as follows:
+
+    from packaging._typing import TYPE_CHECKING
+
+    if TYPE_CHECKING:
+        from typing import ...
+
+Ref: https://github.com/python/mypy/issues/3216
+"""
+
+__all__ = ["TYPE_CHECKING", "cast"]
+
+# The TYPE_CHECKING constant defined by the typing module is False at runtime
+# but True while type checking.
+if False:  # pragma: no cover
+    from typing import TYPE_CHECKING
+else:
+    TYPE_CHECKING = False
+
+# typing's cast syntax requires calling typing.cast at runtime, but we don't
+# want to import typing at runtime. Here, we inform the type checkers that
+# we're importing `typing.cast` as `cast` and re-implement typing.cast's
+# runtime behavior in a block that is ignored by type checkers.
+if TYPE_CHECKING:  # pragma: no cover
+    # not executed at runtime
+    from typing import cast
+else:
+    # executed at runtime
+    def cast(type_, value):  # noqa
+        return value
diff --git a/src/wheel/vendored/packaging/tags.py b/src/wheel/vendored/packaging/tags.py
new file mode 100644
index 0000000..ee529c8
--- /dev/null
+++ b/src/wheel/vendored/packaging/tags.py
@@ -0,0 +1,753 @@
+# Vendored from packaging v20.4.
+#
+# This file is dual licensed under the terms of the Apache License, Version
+# 2.0, and the BSD License. See the LICENSE file in the root of this repository
+# for complete details.
+
+from __future__ import absolute_import
+
+import distutils.util
+
+try:
+    from importlib.machinery import EXTENSION_SUFFIXES
+except ImportError:  # pragma: no cover
+    import imp
+
+    EXTENSION_SUFFIXES = [x[0] for x in imp.get_suffixes()]
+    del imp
+import logging
+import os
+import platform
+import re
+import struct
+import sys
+import sysconfig
+import warnings
+
+from ._typing import TYPE_CHECKING, cast
+
+if TYPE_CHECKING:  # pragma: no cover
+    from typing import (
+        Dict,
+        FrozenSet,
+        IO,
+        Iterable,
+        Iterator,
+        List,
+        Optional,
+        Sequence,
+        Tuple,
+        Union,
+    )
+
+    PythonVersion = Sequence[int]
+    MacVersion = Tuple[int, int]
+    GlibcVersion = Tuple[int, int]
+
+
+logger = logging.getLogger(__name__)
+
+INTERPRETER_SHORT_NAMES = {
+    "python": "py",  # Generic.
+    "cpython": "cp",
+    "pypy": "pp",
+    "ironpython": "ip",
+    "jython": "jy",
+}  # type: Dict[str, str]
+
+
+_32_BIT_INTERPRETER = sys.maxsize <= 2 ** 32
+
+
+class Tag(object):
+    """
+    A representation of the tag triple for a wheel.
+
+    Instances are considered immutable and thus are hashable. Equality checking
+    is also supported.
+    """
+
+    __slots__ = ["_interpreter", "_abi", "_platform"]
+
+    def __init__(self, interpreter, abi, platform):
+        # type: (str, str, str) -> None
+        self._interpreter = interpreter.lower()
+        self._abi = abi.lower()
+        self._platform = platform.lower()
+
+    @property
+    def interpreter(self):
+        # type: () -> str
+        return self._interpreter
+
+    @property
+    def abi(self):
+        # type: () -> str
+        return self._abi
+
+    @property
+    def platform(self):
+        # type: () -> str
+        return self._platform
+
+    def __eq__(self, other):
+        # type: (object) -> bool
+        if not isinstance(other, Tag):
+            return NotImplemented
+
+        return (
+            (self.platform == other.platform)
+            and (self.abi == other.abi)
+            and (self.interpreter == other.interpreter)
+        )
+
+    def __hash__(self):
+        # type: () -> int
+        return hash((self._interpreter, self._abi, self._platform))
+
+    def __str__(self):
+        # type: () -> str
+        return "{}-{}-{}".format(self._interpreter, self._abi, self._platform)
+
+    def __repr__(self):
+        # type: () -> str
+        return "<{self} @ {self_id}>".format(self=self, self_id=id(self))
+
+
+def parse_tag(tag):
+    # type: (str) -> FrozenSet[Tag]
+    """
+    Parses the provided tag (e.g. `py3-none-any`) into a frozenset of Tag instances.
+
+    Returning a set is required due to the possibility that the tag is a
+    compressed tag set.
+    """
+    tags = set()
+    interpreters, abis, platforms = tag.split("-")
+    for interpreter in interpreters.split("."):
+        for abi in abis.split("."):
+            for platform_ in platforms.split("."):
+                tags.add(Tag(interpreter, abi, platform_))
+    return frozenset(tags)
+
+
+def _warn_keyword_parameter(func_name, kwargs):
+    # type: (str, Dict[str, bool]) -> bool
+    """
+    Backwards-compatibility with Python 2.7 to allow treating 'warn' as keyword-only.
+    """
+    if not kwargs:
+        return False
+    elif len(kwargs) > 1 or "warn" not in kwargs:
+        kwargs.pop("warn", None)
+        arg = next(iter(kwargs.keys()))
+        raise TypeError(
+            "{}() got an unexpected keyword argument {!r}".format(func_name, arg)
+        )
+    return kwargs["warn"]
+
+
+def _get_config_var(name, warn=False):
+    # type: (str, bool) -> Union[int, str, None]
+    value = sysconfig.get_config_var(name)
+    if value is None and warn:
+        logger.debug(
+            "Config variable '%s' is unset, Python ABI tag may be incorrect", name
+        )
+    return value
+
+
+def _normalize_string(string):
+    # type: (str) -> str
+    return string.replace(".", "_").replace("-", "_")
+
+
+def _abi3_applies(python_version):
+    # type: (PythonVersion) -> bool
+    """
+    Determine if the Python version supports abi3.
+
+    PEP 384 was first implemented in Python 3.2.
+    """
+    return len(python_version) > 1 and tuple(python_version) >= (3, 2)
+
+
+def _cpython_abis(py_version, warn=False):
+    # type: (PythonVersion, bool) -> List[str]
+    py_version = tuple(py_version)  # To allow for version comparison.
+    abis = []
+    version = _version_nodot(py_version[:2])
+    debug = pymalloc = ucs4 = ""
+    with_debug = _get_config_var("Py_DEBUG", warn)
+    has_refcount = hasattr(sys, "gettotalrefcount")
+    # Windows doesn't set Py_DEBUG, so checking for support of debug-compiled
+    # extension modules is the best option.
+    # https://github.com/pypa/pip/issues/3383#issuecomment-173267692
+    has_ext = "_d.pyd" in EXTENSION_SUFFIXES
+    if with_debug or (with_debug is None and (has_refcount or has_ext)):
+        debug = "d"
+    if py_version < (3, 8):
+        with_pymalloc = _get_config_var("WITH_PYMALLOC", warn)
+        if with_pymalloc or with_pymalloc is None:
+            pymalloc = "m"
+        if py_version < (3, 3):
+            unicode_size = _get_config_var("Py_UNICODE_SIZE", warn)
+            if unicode_size == 4 or (
+                unicode_size is None and sys.maxunicode == 0x10FFFF
+            ):
+                ucs4 = "u"
+    elif debug:
+        # Debug builds can also load "normal" extension modules.
+        # We can also assume no UCS-4 or pymalloc requirement.
+        abis.append("cp{version}".format(version=version))
+    abis.insert(
+        0,
+        "cp{version}{debug}{pymalloc}{ucs4}".format(
+            version=version, debug=debug, pymalloc=pymalloc, ucs4=ucs4
+        ),
+    )
+    return abis
+
+
+def cpython_tags(
+    python_version=None,  # type: Optional[PythonVersion]
+    abis=None,  # type: Optional[Iterable[str]]
+    platforms=None,  # type: Optional[Iterable[str]]
+    **kwargs  # type: bool
+):
+    # type: (...) -> Iterator[Tag]
+    """
+    Yields the tags for a CPython interpreter.
+
+    The tags consist of:
+    - cp<python_version>-<abi>-<platform>
+    - cp<python_version>-abi3-<platform>
+    - cp<python_version>-none-<platform>
+    - cp<less than python_version>-abi3-<platform>  # Older Python versions down to 3.2.
+
+    If python_version only specifies a major version then user-provided ABIs and
+    the 'none' ABItag will be used.
+
+    If 'abi3' or 'none' are specified in 'abis' then they will be yielded at
+    their normal position and not at the beginning.
+    """
+    warn = _warn_keyword_parameter("cpython_tags", kwargs)
+    if not python_version:
+        python_version = sys.version_info[:2]
+
+    interpreter = "cp{}".format(_version_nodot(python_version[:2]))
+
+    if abis is None:
+        if len(python_version) > 1:
+            abis = _cpython_abis(python_version, warn)
+        else:
+            abis = []
+    abis = list(abis)
+    # 'abi3' and 'none' are explicitly handled later.
+    for explicit_abi in ("abi3", "none"):
+        try:
+            abis.remove(explicit_abi)
+        except ValueError:
+            pass
+
+    platforms = list(platforms or _platform_tags())
+    for abi in abis:
+        for platform_ in platforms:
+            yield Tag(interpreter, abi, platform_)
+    if _abi3_applies(python_version):
+        for tag in (Tag(interpreter, "abi3", platform_) for platform_ in platforms):
+            yield tag
+    for tag in (Tag(interpreter, "none", platform_) for platform_ in platforms):
+        yield tag
+
+    if _abi3_applies(python_version):
+        for minor_version in range(python_version[1] - 1, 1, -1):
+            for platform_ in platforms:
+                interpreter = "cp{version}".format(
+                    version=_version_nodot((python_version[0], minor_version))
+                )
+                yield Tag(interpreter, "abi3", platform_)
+
+
+def _generic_abi():
+    # type: () -> Iterator[str]
+    abi = sysconfig.get_config_var("SOABI")
+    if abi:
+        yield _normalize_string(abi)
+
+
+def generic_tags(
+    interpreter=None,  # type: Optional[str]
+    abis=None,  # type: Optional[Iterable[str]]
+    platforms=None,  # type: Optional[Iterable[str]]
+    **kwargs  # type: bool
+):
+    # type: (...) -> Iterator[Tag]
+    """
+    Yields the tags for a generic interpreter.
+
+    The tags consist of:
+    - <interpreter>-<abi>-<platform>
+
+    The "none" ABI will be added if it was not explicitly provided.
+    """
+    warn = _warn_keyword_parameter("generic_tags", kwargs)
+    if not interpreter:
+        interp_name = interpreter_name()
+        interp_version = interpreter_version(warn=warn)
+        interpreter = "".join([interp_name, interp_version])
+    if abis is None:
+        abis = _generic_abi()
+    platforms = list(platforms or _platform_tags())
+    abis = list(abis)
+    if "none" not in abis:
+        abis.append("none")
+    for abi in abis:
+        for platform_ in platforms:
+            yield Tag(interpreter, abi, platform_)
+
+
+def _py_interpreter_range(py_version):
+    # type: (PythonVersion) -> Iterator[str]
+    """
+    Yields Python versions in descending order.
+
+    After the latest version, the major-only version will be yielded, and then
+    all previous versions of that major version.
+    """
+    if len(py_version) > 1:
+        yield "py{version}".format(version=_version_nodot(py_version[:2]))
+    yield "py{major}".format(major=py_version[0])
+    if len(py_version) > 1:
+        for minor in range(py_version[1] - 1, -1, -1):
+            yield "py{version}".format(version=_version_nodot((py_version[0], minor)))
+
+
+def compatible_tags(
+    python_version=None,  # type: Optional[PythonVersion]
+    interpreter=None,  # type: Optional[str]
+    platforms=None,  # type: Optional[Iterable[str]]
+):
+    # type: (...) -> Iterator[Tag]
+    """
+    Yields the sequence of tags that are compatible with a specific version of Python.
+
+    The tags consist of:
+    - py*-none-<platform>
+    - <interpreter>-none-any  # ... if `interpreter` is provided.
+    - py*-none-any
+    """
+    if not python_version:
+        python_version = sys.version_info[:2]
+    platforms = list(platforms or _platform_tags())
+    for version in _py_interpreter_range(python_version):
+        for platform_ in platforms:
+            yield Tag(version, "none", platform_)
+    if interpreter:
+        yield Tag(interpreter, "none", "any")
+    for version in _py_interpreter_range(python_version):
+        yield Tag(version, "none", "any")
+
+
+def _mac_arch(arch, is_32bit=_32_BIT_INTERPRETER):
+    # type: (str, bool) -> str
+    if not is_32bit:
+        return arch
+
+    if arch.startswith("ppc"):
+        return "ppc"
+
+    return "i386"
+
+
+def _mac_binary_formats(version, cpu_arch):
+    # type: (MacVersion, str) -> List[str]
+    formats = [cpu_arch]
+    if cpu_arch == "x86_64":
+        if version < (10, 4):
+            return []
+        formats.extend(["intel", "fat64", "fat32"])
+
+    elif cpu_arch == "i386":
+        if version < (10, 4):
+            return []
+        formats.extend(["intel", "fat32", "fat"])
+
+    elif cpu_arch == "ppc64":
+        # TODO: Need to care about 32-bit PPC for ppc64 through 10.2?
+        if version > (10, 5) or version < (10, 4):
+            return []
+        formats.append("fat64")
+
+    elif cpu_arch == "ppc":
+        if version > (10, 6):
+            return []
+        formats.extend(["fat32", "fat"])
+
+    formats.append("universal")
+    return formats
+
+
+def mac_platforms(version=None, arch=None):
+    # type: (Optional[MacVersion], Optional[str]) -> Iterator[str]
+    """
+    Yields the platform tags for a macOS system.
+
+    The `version` parameter is a two-item tuple specifying the macOS version to
+    generate platform tags for. The `arch` parameter is the CPU architecture to
+    generate platform tags for. Both parameters default to the appropriate value
+    for the current system.
+    """
+    version_str, _, cpu_arch = platform.mac_ver()  # type: ignore
+    if version is None:
+        version = cast("MacVersion", tuple(map(int, version_str.split(".")[:2])))
+    else:
+        version = version
+    if arch is None:
+        arch = _mac_arch(cpu_arch)
+    else:
+        arch = arch
+    for minor_version in range(version[1], -1, -1):
+        compat_version = version[0], minor_version
+        binary_formats = _mac_binary_formats(compat_version, arch)
+        for binary_format in binary_formats:
+            yield "macosx_{major}_{minor}_{binary_format}".format(
+                major=compat_version[0],
+                minor=compat_version[1],
+                binary_format=binary_format,
+            )
+
+
+# From PEP 513.
+def _is_manylinux_compatible(name, glibc_version):
+    # type: (str, GlibcVersion) -> bool
+    # Check for presence of _manylinux module.
+    try:
+        import _manylinux  # noqa
+
+        return bool(getattr(_manylinux, name + "_compatible"))
+    except (ImportError, AttributeError):
+        # Fall through to heuristic check below.
+        pass
+
+    return _have_compatible_glibc(*glibc_version)
+
+
+def _glibc_version_string():
+    # type: () -> Optional[str]
+    # Returns glibc version string, or None if not using glibc.
+    return _glibc_version_string_confstr() or _glibc_version_string_ctypes()
+
+
+def _glibc_version_string_confstr():
+    # type: () -> Optional[str]
+    """
+    Primary implementation of glibc_version_string using os.confstr.
+    """
+    # os.confstr is quite a bit faster than ctypes.DLL. It's also less likely
+    # to be broken or missing. This strategy is used in the standard library
+    # platform module.
+    # https://github.com/python/cpython/blob/fcf1d003bf4f0100c9d0921ff3d70e1127ca1b71/Lib/platform.py#L175-L183
+    try:
+        # os.confstr("CS_GNU_LIBC_VERSION") returns a string like "glibc 2.17".
+        version_string = os.confstr(  # type: ignore[attr-defined] # noqa: F821
+            "CS_GNU_LIBC_VERSION"
+        )
+        assert version_string is not None
+        _, version = version_string.split()  # type: Tuple[str, str]
+    except (AssertionError, AttributeError, OSError, ValueError):
+        # os.confstr() or CS_GNU_LIBC_VERSION not available (or a bad value)...
+        return None
+    return version
+
+
+def _glibc_version_string_ctypes():
+    # type: () -> Optional[str]
+    """
+    Fallback implementation of glibc_version_string using ctypes.
+    """
+    try:
+        import ctypes
+    except ImportError:
+        return None
+
+    # ctypes.CDLL(None) internally calls dlopen(NULL), and as the dlopen
+    # manpage says, "If filename is NULL, then the returned handle is for the
+    # main program". This way we can let the linker do the work to figure out
+    # which libc our process is actually using.
+    #
+    # Note: typeshed is wrong here so we are ignoring this line.
+    process_namespace = ctypes.CDLL(None)  # type: ignore
+    try:
+        gnu_get_libc_version = process_namespace.gnu_get_libc_version
+    except AttributeError:
+        # Symbol doesn't exist -> therefore, we are not linked to
+        # glibc.
+        return None
+
+    # Call gnu_get_libc_version, which returns a string like "2.5"
+    gnu_get_libc_version.restype = ctypes.c_char_p
+    version_str = gnu_get_libc_version()  # type: str
+    # py2 / py3 compatibility:
+    if not isinstance(version_str, str):
+        version_str = version_str.decode("ascii")
+
+    return version_str
+
+
+# Separated out from have_compatible_glibc for easier unit testing.
+def _check_glibc_version(version_str, required_major, minimum_minor):
+    # type: (str, int, int) -> bool
+    # Parse string and check against requested version.
+    #
+    # We use a regexp instead of str.split because we want to discard any
+    # random junk that might come after the minor version -- this might happen
+    # in patched/forked versions of glibc (e.g. Linaro's version of glibc
+    # uses version strings like "2.20-2014.11"). See gh-3588.
+    m = re.match(r"(?P<major>[0-9]+)\.(?P<minor>[0-9]+)", version_str)
+    if not m:
+        warnings.warn(
+            "Expected glibc version with 2 components major.minor,"
+            " got: %s" % version_str,
+            RuntimeWarning,
+        )
+        return False
+    return (
+        int(m.group("major")) == required_major
+        and int(m.group("minor")) >= minimum_minor
+    )
+
+
+def _have_compatible_glibc(required_major, minimum_minor):
+    # type: (int, int) -> bool
+    version_str = _glibc_version_string()
+    if version_str is None:
+        return False
+    return _check_glibc_version(version_str, required_major, minimum_minor)
+
+
+# Python does not provide platform information at sufficient granularity to
+# identify the architecture of the running executable in some cases, so we
+# determine it dynamically by reading the information from the running
+# process. This only applies on Linux, which uses the ELF format.
+class _ELFFileHeader(object):
+    # https://en.wikipedia.org/wiki/Executable_and_Linkable_Format#File_header
+    class _InvalidELFFileHeader(ValueError):
+        """
+        An invalid ELF file header was found.
+        """
+
+    ELF_MAGIC_NUMBER = 0x7F454C46
+    ELFCLASS32 = 1
+    ELFCLASS64 = 2
+    ELFDATA2LSB = 1
+    ELFDATA2MSB = 2
+    EM_386 = 3
+    EM_S390 = 22
+    EM_ARM = 40
+    EM_X86_64 = 62
+    EF_ARM_ABIMASK = 0xFF000000
+    EF_ARM_ABI_VER5 = 0x05000000
+    EF_ARM_ABI_FLOAT_HARD = 0x00000400
+
+    def __init__(self, file):
+        # type: (IO[bytes]) -> None
+        def unpack(fmt):
+            # type: (str) -> int
+            try:
+                (result,) = struct.unpack(
+                    fmt, file.read(struct.calcsize(fmt))
+                )  # type: (int, )
+            except struct.error:
+                raise _ELFFileHeader._InvalidELFFileHeader()
+            return result
+
+        self.e_ident_magic = unpack(">I")
+        if self.e_ident_magic != self.ELF_MAGIC_NUMBER:
+            raise _ELFFileHeader._InvalidELFFileHeader()
+        self.e_ident_class = unpack("B")
+        if self.e_ident_class not in {self.ELFCLASS32, self.ELFCLASS64}:
+            raise _ELFFileHeader._InvalidELFFileHeader()
+        self.e_ident_data = unpack("B")
+        if self.e_ident_data not in {self.ELFDATA2LSB, self.ELFDATA2MSB}:
+            raise _ELFFileHeader._InvalidELFFileHeader()
+        self.e_ident_version = unpack("B")
+        self.e_ident_osabi = unpack("B")
+        self.e_ident_abiversion = unpack("B")
+        self.e_ident_pad = file.read(7)
+        format_h = "<H" if self.e_ident_data == self.ELFDATA2LSB else ">H"
+        format_i = "<I" if self.e_ident_data == self.ELFDATA2LSB else ">I"
+        format_q = "<Q" if self.e_ident_data == self.ELFDATA2LSB else ">Q"
+        format_p = format_i if self.e_ident_class == self.ELFCLASS32 else format_q
+        self.e_type = unpack(format_h)
+        self.e_machine = unpack(format_h)
+        self.e_version = unpack(format_i)
+        self.e_entry = unpack(format_p)
+        self.e_phoff = unpack(format_p)
+        self.e_shoff = unpack(format_p)
+        self.e_flags = unpack(format_i)
+        self.e_ehsize = unpack(format_h)
+        self.e_phentsize = unpack(format_h)
+        self.e_phnum = unpack(format_h)
+        self.e_shentsize = unpack(format_h)
+        self.e_shnum = unpack(format_h)
+        self.e_shstrndx = unpack(format_h)
+
+
+def _get_elf_header():
+    # type: () -> Optional[_ELFFileHeader]
+    try:
+        with open(sys.executable, "rb") as f:
+            elf_header = _ELFFileHeader(f)
+    except (IOError, OSError, TypeError, _ELFFileHeader._InvalidELFFileHeader):
+        return None
+    return elf_header
+
+
+def _is_linux_armhf():
+    # type: () -> bool
+    # hard-float ABI can be detected from the ELF header of the running
+    # process
+    # https://static.docs.arm.com/ihi0044/g/aaelf32.pdf
+    elf_header = _get_elf_header()
+    if elf_header is None:
+        return False
+    result = elf_header.e_ident_class == elf_header.ELFCLASS32
+    result &= elf_header.e_ident_data == elf_header.ELFDATA2LSB
+    result &= elf_header.e_machine == elf_header.EM_ARM
+    result &= (
+        elf_header.e_flags & elf_header.EF_ARM_ABIMASK
+    ) == elf_header.EF_ARM_ABI_VER5
+    result &= (
+        elf_header.e_flags & elf_header.EF_ARM_ABI_FLOAT_HARD
+    ) == elf_header.EF_ARM_ABI_FLOAT_HARD
+    return result
+
+
+def _is_linux_i686():
+    # type: () -> bool
+    elf_header = _get_elf_header()
+    if elf_header is None:
+        return False
+    result = elf_header.e_ident_class == elf_header.ELFCLASS32
+    result &= elf_header.e_ident_data == elf_header.ELFDATA2LSB
+    result &= elf_header.e_machine == elf_header.EM_386
+    return result
+
+
+def _have_compatible_manylinux_abi(arch):
+    # type: (str) -> bool
+    if arch == "armv7l":
+        return _is_linux_armhf()
+    if arch == "i686":
+        return _is_linux_i686()
+    return True
+
+
+def _linux_platforms(is_32bit=_32_BIT_INTERPRETER):
+    # type: (bool) -> Iterator[str]
+    linux = _normalize_string(distutils.util.get_platform())
+    if is_32bit:
+        if linux == "linux_x86_64":
+            linux = "linux_i686"
+        elif linux == "linux_aarch64":
+            linux = "linux_armv7l"
+    manylinux_support = []
+    _, arch = linux.split("_", 1)
+    if _have_compatible_manylinux_abi(arch):
+        if arch in {"x86_64", "i686", "aarch64", "armv7l", "ppc64", "ppc64le", "s390x"}:
+            manylinux_support.append(
+                ("manylinux2014", (2, 17))
+            )  # CentOS 7 w/ glibc 2.17 (PEP 599)
+        if arch in {"x86_64", "i686"}:
+            manylinux_support.append(
+                ("manylinux2010", (2, 12))
+            )  # CentOS 6 w/ glibc 2.12 (PEP 571)
+            manylinux_support.append(
+                ("manylinux1", (2, 5))
+            )  # CentOS 5 w/ glibc 2.5 (PEP 513)
+    manylinux_support_iter = iter(manylinux_support)
+    for name, glibc_version in manylinux_support_iter:
+        if _is_manylinux_compatible(name, glibc_version):
+            yield linux.replace("linux", name)
+            break
+    # Support for a later manylinux implies support for an earlier version.
+    for name, _ in manylinux_support_iter:
+        yield linux.replace("linux", name)
+    yield linux
+
+
+def _generic_platforms():
+    # type: () -> Iterator[str]
+    yield _normalize_string(distutils.util.get_platform())
+
+
+def _platform_tags():
+    # type: () -> Iterator[str]
+    """
+    Provides the platform tags for this installation.
+    """
+    if platform.system() == "Darwin":
+        return mac_platforms()
+    elif platform.system() == "Linux":
+        return _linux_platforms()
+    else:
+        return _generic_platforms()
+
+
+def interpreter_name():
+    # type: () -> str
+    """
+    Returns the name of the running interpreter.
+    """
+    try:
+        name = sys.implementation.name  # type: ignore
+    except AttributeError:  # pragma: no cover
+        # Python 2.7 compatibility.
+        name = platform.python_implementation().lower()
+    return INTERPRETER_SHORT_NAMES.get(name) or name
+
+
+def interpreter_version(**kwargs):
+    # type: (bool) -> str
+    """
+    Returns the version of the running interpreter.
+    """
+    warn = _warn_keyword_parameter("interpreter_version", kwargs)
+    version = _get_config_var("py_version_nodot", warn=warn)
+    if version:
+        version = str(version)
+    else:
+        version = _version_nodot(sys.version_info[:2])
+    return version
+
+
+def _version_nodot(version):
+    # type: (PythonVersion) -> str
+    if any(v >= 10 for v in version):
+        sep = "_"
+    else:
+        sep = ""
+    return sep.join(map(str, version))
+
+
+def sys_tags(**kwargs):
+    # type: (bool) -> Iterator[Tag]
+    """
+    Returns the sequence of tag triples for the running interpreter.
+
+    The order of the sequence corresponds to priority order for the
+    interpreter, from most to least important.
+    """
+    warn = _warn_keyword_parameter("sys_tags", kwargs)
+
+    interp_name = interpreter_name()
+    if interp_name == "cp":
+        for tag in cpython_tags(warn=warn):
+            yield tag
+    else:
+        for tag in generic_tags():
+            yield tag
+
+    for tag in compatible_tags():
+        yield tag