import os
import re
import sys
from typing import List, Optional

from pip._internal.locations import site_packages, user_site
from pip._internal.utils.virtualenv import (
    running_under_virtualenv,
    virtualenv_no_global,
)

__all__ = [
    "egg_link_path_from_sys_path",
    "egg_link_path_from_location",
]


def _egg_link_names(raw_name: str) -> List[str]:
    """
    Convert a Name metadata value to a .egg-link name, by applying
    the same substitution as pkg_resources's safe_name function.
    Note: we cannot use canonicalize_name because it has a different logic.

    We also look for the raw name (without normalization) as setuptools 69 changed
    the way it names .egg-link files (https://github.com/pypa/setuptools/issues/4167).
    """
    return [
        re.sub("[^A-Za-z0-9.]+", "-", raw_name) + ".egg-link",
        f"{raw_name}.egg-link",
    ]


def egg_link_path_from_sys_path(raw_name: str) -> Optional[str]:
    """
    Look for a .egg-link file for project name, by walking sys.path.
    """
    egg_link_names = _egg_link_names(raw_name)
    for path_item in sys.path:
        for egg_link_name in egg_link_names:
            egg_link = os.path.join(path_item, egg_link_name)
            if os.path.isfile(egg_link):
                return egg_link
    return None


def egg_link_path_from_location(raw_name: str) -> Optional[str]:
    """
    Return the path for the .egg-link file if it exists, otherwise, None.

    There's 3 scenarios:
    1) not in a virtualenv
       try to find in site.USER_SITE, then site_packages
    2) in a no-global virtualenv
       try to find in site_packages
    3) in a yes-global virtualenv
       try to find in site_packages, then site.USER_SITE
       (don't look in global location)

    For #1 and #3, there could be odd cases, where there's an egg-link in 2
    locations.

    This method will just return the first one found.
    """
    sites: List[str] = []
    if running_under_virtualenv():
        sites.append(site_packages)
        if not virtualenv_no_global() and user_site:
            sites.append(user_site)
    else:
        if user_site:
            sites.append(user_site)
        sites.append(site_packages)

    egg_link_names = _egg_link_names(raw_name)
    for site in sites:
        for egg_link_name in egg_link_names:
            egglink = os.path.join(site, egg_link_name)
            if os.path.isfile(egglink):
                return egglink
    return None

import os
import string
import urllib.parse
import urllib.request

from .compat import WINDOWS


def path_to_url(path: str) -> str:
    """
    Convert a path to a file: URL.  The path will be made absolute and have
    quoted path parts.
    """
    path = os.path.normpath(os.path.abspath(path))
    url = urllib.parse.urljoin("file:", urllib.request.pathname2url(path))
    return url


def url_to_path(url: str) -> str:
    """
    Convert a file: URL to a path.
    """
    assert url.startswith(
        "file:"
    ), f"You can only turn file: urls into filenames (not {url!r})"

    _, netloc, path, _, _ = urllib.parse.urlsplit(url)

    if not netloc or netloc == "localhost":
        # According to RFC 8089, same as empty authority.
        netloc = ""
    elif WINDOWS:
        # If we have a UNC path, prepend UNC share notation.
        netloc = "\\\\" + netloc
    else:
        raise ValueError(
            f"non-local file URIs are not supported on this platform: {url!r}"
        )

    path = urllib.request.url2pathname(netloc + path)

    # On Windows, urlsplit parses the path as something like "/C:/Users/foo".
    # This creates issues for path-related functions like io.open(), so we try
    # to detect and strip the leading slash.
    if (
        WINDOWS
        and not netloc  # Not UNC.
        and len(path) >= 3
        and path[0] == "/"  # Leading slash to strip.
        and path[1] in string.ascii_letters  # Drive letter.
        and path[2:4] in (":", ":/")  # Colon + end of string, or colon + absolute path.
    ):
        path = path[1:]

    return path

# SPDX-FileCopyrightText: 2015 Eric Larson
#
# SPDX-License-Identifier: Apache-2.0

"""CacheControl import Interface.

Make it easy to import from cachecontrol without long namespaces.
"""
__author__ = "Eric Larson"
__email__ = "eric@ionrock.org"
__version__ = "0.14.0"

from pip._vendor.cachecontrol.adapter import CacheControlAdapter
from pip._vendor.cachecontrol.controller import CacheController
from pip._vendor.cachecontrol.wrapper import CacheControl

__all__ = [
    "__author__",
    "__email__",
    "__version__",
    "CacheControlAdapter",
    "CacheController",
    "CacheControl",
]

import logging

logging.getLogger(__name__).addHandler(logging.NullHandler())

# SPDX-FileCopyrightText: 2015 Eric Larson
#
# SPDX-License-Identifier: Apache-2.0
from __future__ import annotations

import logging
from argparse import ArgumentParser
from typing import TYPE_CHECKING

from pip._vendor import requests

from pip._vendor.cachecontrol.adapter import CacheControlAdapter
from pip._vendor.cachecontrol.cache import DictCache
from pip._vendor.cachecontrol.controller import logger

if TYPE_CHECKING:
    from argparse import Namespace

    from pip._vendor.cachecontrol.controller import CacheController


def setup_logging() -> None:
    logger.setLevel(logging.DEBUG)
    handler = logging.StreamHandler()
    logger.addHandler(handler)


def get_session() -> requests.Session:
    adapter = CacheControlAdapter(
        DictCache(), cache_etags=True, serializer=None, heuristic=None
    )
    sess = requests.Session()
    sess.mount("http://", adapter)
    sess.mount("https://", adapter)

    sess.cache_controller = adapter.controller  # type: ignore[attr-defined]
    return sess


def get_args() -> Namespace:
    parser = ArgumentParser()
    parser.add_argument("url", help="The URL to try and cache")
    return parser.parse_args()


def main() -> None:
    args = get_args()
    sess = get_session()

    # Make a request to get a response
    resp = sess.get(args.url)

    # Turn on logging
    setup_logging()

    # try setting the cache
    cache_controller: CacheController = (
        sess.cache_controller  # type: ignore[attr-defined]
    )
    cache_controller.cache_response(resp.request, resp.raw)

    # Now try to get it
    if cache_controller.cached_request(resp.request):
        print("Cached!")
    else:
        print("Not cached :(")


if __name__ == "__main__":
    main()

import logging
import os.path
import pathlib
import re
import urllib.parse
import urllib.request
from dataclasses import replace
from typing import List, Optional, Tuple

from pip._internal.exceptions import BadCommand, InstallationError
from pip._internal.utils.misc import HiddenText, display_path, hide_url
from pip._internal.utils.subprocess import make_command
from pip._internal.vcs.versioncontrol import (
    AuthInfo,
    RemoteNotFoundError,
    RemoteNotValidError,
    RevOptions,
    VersionControl,
    find_path_to_project_root_from_repo_root,
    vcs,
)

urlsplit = urllib.parse.urlsplit
urlunsplit = urllib.parse.urlunsplit


logger = logging.getLogger(__name__)


GIT_VERSION_REGEX = re.compile(
    r"^git version "  # Prefix.
    r"(\d+)"  # Major.
    r"\.(\d+)"  # Dot, minor.
    r"(?:\.(\d+))?"  # Optional dot, patch.
    r".*$"  # Suffix, including any pre- and post-release segments we don't care about.
)

HASH_REGEX = re.compile("^[a-fA-F0-9]{40}$")

# SCP (Secure copy protocol) shorthand. e.g. 'git@example.com:foo/bar.git'
SCP_REGEX = re.compile(
    r"""^
    # Optional user, e.g. 'git@'
    (\w+@)?
    # Server, e.g. 'github.com'.
    ([^/:]+):
    # The server-side path. e.g. 'user/project.git'. Must start with an
    # alphanumeric character so as not to be confusable with a Windows paths
    # like 'C:/foo/bar' or 'C:\foo\bar'.
    (\w[^:]*)
    $""",
    re.VERBOSE,
)


def looks_like_hash(sha: str) -> bool:
    return bool(HASH_REGEX.match(sha))


class Git(VersionControl):
    name = "git"
    dirname = ".git"
    repo_name = "clone"
    schemes = (
        "git+http",
        "git+https",
        "git+ssh",
        "git+git",
        "git+file",
    )
    # Prevent the user's environment variables from interfering with pip:
    # https://github.com/pypa/pip/issues/1130
    unset_environ = ("GIT_DIR", "GIT_WORK_TREE")
    default_arg_rev = "HEAD"

    @staticmethod
    def get_base_rev_args(rev: str) -> List[str]:
        return [rev]

    def is_immutable_rev_checkout(self, url: str, dest: str) -> bool:
        _, rev_options = self.get_url_rev_options(hide_url(url))
        if not rev_options.rev:
            return False
        if not self.is_commit_id_equal(dest, rev_options.rev):
            # the current commit is different from rev,
            # which means rev was something else than a commit hash
            return False
        # return False in the rare case rev is both a commit hash
        # and a tag or a branch; we don't want to cache in that case
        # because that branch/tag could point to something else in the future
        is_tag_or_branch = bool(self.get_revision_sha(dest, rev_options.rev)[0])
        return not is_tag_or_branch

    def get_git_version(self) -> Tuple[int, ...]:
        version = self.run_command(
            ["version"],
            command_desc="git version",
            show_stdout=False,
            stdout_only=True,
        )
        match = GIT_VERSION_REGEX.match(version)
        if not match:
            logger.warning("Can't parse git version: %s", version)
            return ()
        return (int(match.group(1)), int(match.group(2)))

    @classmethod
    def get_current_branch(cls, location: str) -> Optional[str]:
        """
        Return the current branch, or None if HEAD isn't at a branch
        (e.g. detached HEAD).
        """
        # git-symbolic-ref exits with empty stdout if "HEAD" is a detached
        # HEAD rather than a symbolic ref.  In addition, the -q causes the
        # command to exit with status code 1 instead of 128 in this case
        # and to suppress the message to stderr.
        args = ["symbolic-ref", "-q", "HEAD"]
        output = cls.run_command(
            args,
            extra_ok_returncodes=(1,),
            show_stdout=False,
            stdout_only=True,
            cwd=location,
        )
        ref = output.strip()

        if ref.startswith("refs/heads/"):
            return ref[len("refs/heads/") :]

        return None

    @classmethod
    def get_revision_sha(cls, dest: str, rev: str) -> Tuple[Optional[str], bool]:
        """
        Return (sha_or_none, is_branch), where sha_or_none is a commit hash
        if the revision names a remote branch or tag, otherwise None.

        Args:
          dest: the repository directory.
          rev: the revision name.
        """
        # Pass rev to pre-filter the list.
        output = cls.run_command(
            ["show-ref", rev],
            cwd=dest,
            show_stdout=False,
            stdout_only=True,
            on_returncode="ignore",
        )
        refs = {}
        # NOTE: We do not use splitlines here since that would split on other
        #       unicode separators, which can be maliciously used to install a
        #       different revision.
        for line in output.strip().split("\n"):
            line = line.rstrip("\r")
            if not line:
                continue
            try:
                ref_sha, ref_name = line.split(" ", maxsplit=2)
            except ValueError:
                # Include the offending line to simplify troubleshooting if
                # this error ever occurs.
                raise ValueError(f"unexpected show-ref line: {line!r}")

            refs[ref_name] = ref_sha

        branch_ref = f"refs/remotes/origin/{rev}"
        tag_ref = f"refs/tags/{rev}"

        sha = refs.get(branch_ref)
        if sha is not None:
            return (sha, True)

        sha = refs.get(tag_ref)

        return (sha, False)

    @classmethod
    def _should_fetch(cls, dest: str, rev: str) -> bool:
        """
        Return true if rev is a ref or is a commit that we don't have locally.

        Branches and tags are not considered in this method because they are
        assumed to be always available locally (which is a normal outcome of
        ``git clone`` and ``git fetch --tags``).
        """
        if rev.startswith("refs/"):
            # Always fetch remote refs.
            return True

        if not looks_like_hash(rev):
            # Git fetch would fail with abbreviated commits.
            return False

        if cls.has_commit(dest, rev):
            # Don't fetch if we have the commit locally.
            return False

        return True

    @classmethod
    def resolve_revision(
        cls, dest: str, url: HiddenText, rev_options: RevOptions
    ) -> RevOptions:
        """
        Resolve a revision to a new RevOptions object with the SHA1 of the
        branch, tag, or ref if found.

        Args:
          rev_options: a RevOptions object.
        """
        rev = rev_options.arg_rev
        # The arg_rev property's implementation for Git ensures that the
        # rev return value is always non-None.
        assert rev is not None

        sha, is_branch = cls.get_revision_sha(dest, rev)

        if sha is not None:
            rev_options = rev_options.make_new(sha)
            rev_options = replace(rev_options, branch_name=(rev if is_branch else None))

            return rev_options

        # Do not show a warning for the common case of something that has
        # the form of a Git commit hash.
        if not looks_like_hash(rev):
            logger.warning(
                "Did not find branch or tag '%s', assuming revision or ref.",
                rev,
            )

        if not cls._should_fetch(dest, rev):
            return rev_options

        # fetch the requested revision
        cls.run_command(
            make_command("fetch", "-q", url, rev_options.to_args()),
            cwd=dest,
        )
        # Change the revision to the SHA of the ref we fetched
        sha = cls.get_revision(dest, rev="FETCH_HEAD")
        rev_options = rev_options.make_new(sha)

        return rev_options

    @classmethod
    def is_commit_id_equal(cls, dest: str, name: Optional[str]) -> bool:
        """
        Return whether the current commit hash equals the given name.

        Args:
          dest: the repository directory.
          name: a string name.
        """
        if not name:
            # Then avoid an unnecessary subprocess call.
            return False

        return cls.get_revision(dest) == name

    def fetch_new(
        self, dest: str, url: HiddenText, rev_options: RevOptions, verbosity: int
    ) -> None:
        rev_display = rev_options.to_display()
        logger.info("Cloning %s%s to %s", url, rev_display, display_path(dest))
        if verbosity <= 0:
            flags: Tuple[str, ...] = ("--quiet",)
        elif verbosity == 1:
            flags = ()
        else:
            flags = ("--verbose", "--progress")
        if self.get_git_version() >= (2, 17):
            # Git added support for partial clone in 2.17
            # https://git-scm.com/docs/partial-clone
            # Speeds up cloning by functioning without a complete copy of repository
            self.run_command(
                make_command(
                    "clone",
                    "--filter=blob:none",
                    *flags,
                    url,
                    dest,
                )
            )
        else:
            self.run_command(make_command("clone", *flags, url, dest))

        if rev_options.rev:
            # Then a specific revision was requested.
            rev_options = self.resolve_revision(dest, url, rev_options)
            branch_name = getattr(rev_options, "branch_name", None)
            logger.debug("Rev options %s, branch_name %s", rev_options, branch_name)
            if branch_name is None:
                # Only do a checkout if the current commit id doesn't match
                # the requested revision.
                if not self.is_commit_id_equal(dest, rev_options.rev):
                    cmd_args = make_command(
                        "checkout",
                        "-q",
                        rev_options.to_args(),
                    )
                    self.run_command(cmd_args, cwd=dest)
            elif self.get_current_branch(dest) != branch_name:
                # Then a specific branch was requested, and that branch
                # is not yet checked out.
                track_branch = f"origin/{branch_name}"
                cmd_args = [
                    "checkout",
                    "-b",
                    branch_name,
                    "--track",
                    track_branch,
                ]
                self.run_command(cmd_args, cwd=dest)
        else:
            sha = self.get_revision(dest)
            rev_options = rev_options.make_new(sha)

        logger.info("Resolved %s to commit %s", url, rev_options.rev)

        #: repo may contain submodules
        self.update_submodules(dest)

    def switch(self, dest: str, url: HiddenText, rev_options: RevOptions) -> None:
        self.run_command(
            make_command("config", "remote.origin.url", url),
            cwd=dest,
        )
        cmd_args = make_command("checkout", "-q", rev_options.to_args())
        self.run_command(cmd_args, cwd=dest)

        self.update_submodules(dest)

    def update(self, dest: str, url: HiddenText, rev_options: RevOptions) -> None:
        # First fetch changes from the default remote
        if self.get_git_version() >= (1, 9):
            # fetch tags in addition to everything else
            self.run_command(["fetch", "-q", "--tags"], cwd=dest)
        else:
            self.run_command(["fetch", "-q"], cwd=dest)
        # Then reset to wanted revision (maybe even origin/master)
        rev_options = self.resolve_revision(dest, url, rev_options)
        cmd_args = make_command("reset", "--hard", "-q", rev_options.to_args())
        self.run_command(cmd_args, cwd=dest)
        #: update submodules
        self.update_submodules(dest)

    @classmethod
    def get_remote_url(cls, location: str) -> str:
        """
        Return URL of the first remote encountered.

        Raises RemoteNotFoundError if the repository does not have a remote
        url configured.
        """
        # We need to pass 1 for extra_ok_returncodes since the command
        # exits with return code 1 if there are no matching lines.
        stdout = cls.run_command(
            ["config", "--get-regexp", r"remote\..*\.url"],
            extra_ok_returncodes=(1,),
            show_stdout=False,
            stdout_only=True,
            cwd=location,
        )
        remotes = stdout.splitlines()
        try:
            found_remote = remotes[0]
        except IndexError:
            raise RemoteNotFoundError

        for remote in remotes:
            if remote.startswith("remote.origin.url "):
                found_remote = remote
                break
        url = found_remote.split(" ")[1]
        return cls._git_remote_to_pip_url(url.strip())

    @staticmethod
    def _git_remote_to_pip_url(url: str) -> str:
        """
        Convert a remote url from what git uses to what pip accepts.

        There are 3 legal forms **url** may take:

            1. A fully qualified url: ssh://git@example.com/foo/bar.git
            2. A local project.git folder: /path/to/bare/repository.git
            3. SCP shorthand for form 1: git@example.com:foo/bar.git

        Form 1 is output as-is. Form 2 must be converted to URI and form 3 must
        be converted to form 1.

        See the corresponding test test_git_remote_url_to_pip() for examples of
        sample inputs/outputs.
        """
        if re.match(r"\w+://", url):
            # This is already valid. Pass it though as-is.
            return url
        if os.path.exists(url):
            # A local bare remote (git clone --mirror).
            # Needs a file:// prefix.
            return pathlib.PurePath(url).as_uri()
        scp_match = SCP_REGEX.match(url)
        if scp_match:
            # Add an ssh:// prefix and replace the ':' with a '/'.
            return scp_match.expand(r"ssh://\1\2/\3")
        # Otherwise, bail out.
        raise RemoteNotValidError(url)

    @classmethod
    def has_commit(cls, location: str, rev: str) -> bool:
        """
        Check if rev is a commit that is available in the local repository.
        """
        try:
            cls.run_command(
                ["rev-parse", "-q", "--verify", "sha^" + rev],
                cwd=location,
                log_failed_cmd=False,
            )
        except InstallationError:
            return False
        else:
            return True

    @classmethod
    def get_revision(cls, location: str, rev: Optional[str] = None) -> str:
        if rev is None:
            rev = "HEAD"
        current_rev = cls.run_command(
            ["rev-parse", rev],
            show_stdout=False,
            stdout_only=True,
            cwd=location,
        )
        return current_rev.strip()

    @classmethod
    def get_subdirectory(cls, location: str) -> Optional[str]:
        """
        Return the path to Python project root, relative to the repo root.
        Return None if the project root is in the repo root.
        """
        # find the repo root
        git_dir = cls.run_command(
            ["rev-parse", "--git-dir"],
            show_stdout=False,
            stdout_only=True,
            cwd=location,
        ).strip()
        if not os.path.isabs(git_dir):
            git_dir = os.path.join(location, git_dir)
        repo_root = os.path.abspath(os.path.join(git_dir, ".."))
        return find_path_to_project_root_from_repo_root(location, repo_root)

    @classmethod
    def get_url_rev_and_auth(cls, url: str) -> Tuple[str, Optional[str], AuthInfo]:
        """
        Prefixes stub URLs like 'user@hostname:user/repo.git' with 'ssh://'.
        That's required because although they use SSH they sometimes don't
        work with a ssh:// scheme (e.g. GitHub). But we need a scheme for
        parsing. Hence we remove it again afterwards and return it as a stub.
        """
        # Works around an apparent Git bug
        # (see https://article.gmane.org/gmane.comp.version-control.git/146500)
        scheme, netloc, path, query, fragment = urlsplit(url)
        if scheme.endswith("file"):
            initial_slashes = path[: -len(path.lstrip("/"))]
            newpath = initial_slashes + urllib.request.url2pathname(path).replace(
                "\\", "/"
            ).lstrip("/")
            after_plus = scheme.find("+") + 1
            url = scheme[:after_plus] + urlunsplit(
                (scheme[after_plus:], netloc, newpath, query, fragment),
            )

        if "://" not in url:
            assert "file:" not in url
            url = url.replace("git+", "git+ssh://")
            url, rev, user_pass = super().get_url_rev_and_auth(url)
            url = url.replace("ssh://", "")
        else:
            url, rev, user_pass = super().get_url_rev_and_auth(url)

        return url, rev, user_pass

    @classmethod
    def update_submodules(cls, location: str) -> None:
        if not os.path.exists(os.path.join(location, ".gitmodules")):
            return
        cls.run_command(
            ["submodule", "update", "--init", "--recursive", "-q"],
            cwd=location,
        )

    @classmethod
    def get_repository_root(cls, location: str) -> Optional[str]:
        loc = super().get_repository_root(location)
        if loc:
            return loc
        try:
            r = cls.run_command(
                ["rev-parse", "--show-toplevel"],
                cwd=location,
                show_stdout=False,
                stdout_only=True,
                on_returncode="raise",
                log_failed_cmd=False,
            )
        except BadCommand:
            logger.debug(
                "could not determine if %s is under git control "
                "because git is not available",
                location,
            )
            return None
        except InstallationError:
            return None
        return os.path.normpath(r.rstrip("\r\n"))

    @staticmethod
    def should_add_vcs_url_prefix(repo_url: str) -> bool:
        """In either https or ssh form, requirements must be prefixed with git+."""
        return True


vcs.register(Git)

import os
import sys
from typing import Optional, Tuple


def glibc_version_string() -> 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() -> 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
    if sys.platform == "win32":
        return None
    try:
        gnu_libc_version = os.confstr("CS_GNU_LIBC_VERSION")
        if gnu_libc_version is None:
            return None
        # os.confstr("CS_GNU_LIBC_VERSION") returns a string like "glibc 2.17":
        _, version = gnu_libc_version.split()
    except (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() -> 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.
    #
    # We must also handle the special case where the executable is not a
    # dynamically linked executable. This can occur when using musl libc,
    # for example. In this situation, dlopen() will error, leading to an
    # OSError. Interestingly, at least in the case of musl, there is no
    # errno set on the OSError. The single string argument used to construct
    # OSError comes from libc itself and is therefore not portable to
    # hard code here. In any case, failure to call dlopen() means we
    # can't proceed, so we bail on our attempt.
    try:
        process_namespace = ctypes.CDLL(None)
    except OSError:
        return None

    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: str = gnu_get_libc_version()
    # py2 / py3 compatibility:
    if not isinstance(version_str, str):
        version_str = version_str.decode("ascii")

    return version_str


# platform.libc_ver regularly returns completely nonsensical glibc
# versions. E.g. on my computer, platform says:
#
#   ~$ python2.7 -c 'import platform; print(platform.libc_ver())'
#   ('glibc', '2.7')
#   ~$ python3.5 -c 'import platform; print(platform.libc_ver())'
#   ('glibc', '2.9')
#
# But the truth is:
#
#   ~$ ldd --version
#   ldd (Debian GLIBC 2.22-11) 2.22
#
# This is unfortunate, because it means that the linehaul data on libc
# versions that was generated by pip 8.1.2 and earlier is useless and
# misleading. Solution: instead of using platform, use our code that actually
# works.
def libc_ver() -> Tuple[str, str]:
    """Try to determine the glibc version

    Returns a tuple of strings (lib, version) which default to empty strings
    in case the lookup fails.
    """
    glibc_version = glibc_version_string()
    if glibc_version is None:
        return ("", "")
    else:
        return ("glibc", glibc_version)