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# The following comment should be removed at some point in the future.
# mypy: strict-optional=False
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:
# os.confstr("CS_GNU_LIBC_VERSION") returns a string like "glibc 2.17":
_, version = os.confstr("CS_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.
process_namespace = ctypes.CDLL(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 = 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)
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