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GeezerVison is showing github.com — gh-78997: AttributeError if loading fails in LibraryLoader.__getattr__ by farfella · Pull Request #25177 · python/cpython

gh-78997: AttributeError if loading fails in LibraryLoader.__getattr__ #25177

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Merged
FFY00 merged 7 commits into python:main from farfella:bpo-34816
Dec 15, 2022

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Merged

gh-78997: AttributeError if loading fails in LibraryLoader.__getattr__ #25177

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aa340b8
bpo-34816: Raise AttributeError if loading fails in ctypes.LibraryLoa…
farfella Dec 15, 2022
b8aaba9
merging in 3.11 updates
farfella Dec 15, 2022
f7487c4
adding new line at end of file for docs
farfella Dec 15, 2022
76f0039
updating news per feedback
farfella Dec 15, 2022
12d77d2
Update Misc/NEWS.d/next/Windows/2021-04-08-00-36-37.bpo-34816.4Xe0id.rst
FFY00 Dec 15, 2022
6c66904
Update Misc/NEWS.d/next/Windows/2021-04-08-00-36-37.bpo-34816.4Xe0id.rst
FFY00 Dec 15, 2022
f151341
Update Misc/NEWS.d/next/Windows/2021-04-08-00-36-37.bpo-34816.4Xe0id.rst
FFY00 Dec 15, 2022
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5 changes: 4 additions & 1 deletion 5 Lib/ctypes/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -444,7 +444,10 @@ def __init__(self, dlltype):
def __getattr__(self, name):
if name[0] == '_':
raise AttributeError(name)
dll = self._dlltype(name)
try:
dll = self._dlltype(name)
except OSError:
raise AttributeError(name)
setattr(self, name, dll)
return dll

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188 changes: 188 additions & 0 deletions 188 Lib/ctypes/test/test_loading.py
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Original file line number Diff line number Diff line change
@@ -0,0 +1,188 @@
from ctypes import *
import os
import shutil
import subprocess
import sys
import unittest
import test.support
from test.support import import_helper
from test.support import os_helper
from ctypes.util import find_library

libc_name = None

def setUpModule():
global libc_name
if os.name == "nt":
libc_name = find_library("c")
elif sys.platform == "cygwin":
libc_name = "cygwin1.dll"
else:
libc_name = find_library("c")

if test.support.verbose:
print("libc_name is", libc_name)

class LoaderTest(unittest.TestCase):

unknowndll = "xxrandomnamexx"

def test_load(self):
if libc_name is None:
self.skipTest('could not find libc')
CDLL(libc_name)
CDLL(os.path.basename(libc_name))
self.assertRaises(OSError, CDLL, self.unknowndll)

def test_load_version(self):
if libc_name is None:
self.skipTest('could not find libc')
if os.path.basename(libc_name) != 'libc.so.6':
self.skipTest('wrong libc path for test')
cdll.LoadLibrary("libc.so.6")
# linux uses version, libc 9 should not exist
self.assertRaises(OSError, cdll.LoadLibrary, "libc.so.9")
self.assertRaises(OSError, cdll.LoadLibrary, self.unknowndll)

def test_find(self):
for name in ("c", "m"):
lib = find_library(name)
if lib:
cdll.LoadLibrary(lib)
CDLL(lib)

@unittest.skipUnless(os.name == "nt",
'test specific to Windows')
def test_load_library(self):
# CRT is no longer directly loadable. See issue23606 for the
# discussion about alternative approaches.
#self.assertIsNotNone(libc_name)
if test.support.verbose:
print(find_library("kernel32"))
print(find_library("user32"))

if os.name == "nt":
windll.kernel32.GetModuleHandleW
windll["kernel32"].GetModuleHandleW
windll.LoadLibrary("kernel32").GetModuleHandleW
WinDLL("kernel32").GetModuleHandleW
# embedded null character
self.assertRaises(ValueError, windll.LoadLibrary, "kernel32\0")

@unittest.skipUnless(os.name == "nt",
'test specific to Windows')
def test_load_ordinal_functions(self):
import _ctypes_test
dll = WinDLL(_ctypes_test.__file__)
# We load the same function both via ordinal and name
func_ord = dll[2]
func_name = dll.GetString
# addressof gets the address where the function pointer is stored
a_ord = addressof(func_ord)
a_name = addressof(func_name)
f_ord_addr = c_void_p.from_address(a_ord).value
f_name_addr = c_void_p.from_address(a_name).value
self.assertEqual(hex(f_ord_addr), hex(f_name_addr))

self.assertRaises(AttributeError, dll.__getitem__, 1234)

@unittest.skipUnless(os.name == "nt", 'Windows-specific test')
def test_1703286_A(self):
from _ctypes import LoadLibrary, FreeLibrary
# On winXP 64-bit, advapi32 loads at an address that does
# NOT fit into a 32-bit integer. FreeLibrary must be able
# to accept this address.

# These are tests for https://www.python.org/sf/1703286
handle = LoadLibrary("advapi32")
FreeLibrary(handle)

@unittest.skipUnless(os.name == "nt", 'Windows-specific test')
def test_1703286_B(self):
# Since on winXP 64-bit advapi32 loads like described
# above, the (arbitrarily selected) CloseEventLog function
# also has a high address. 'call_function' should accept
# addresses so large.
from _ctypes import call_function
advapi32 = windll.advapi32
# Calling CloseEventLog with a NULL argument should fail,
# but the call should not segfault or so.
self.assertEqual(0, advapi32.CloseEventLog(None))
windll.kernel32.GetProcAddress.argtypes = c_void_p, c_char_p
windll.kernel32.GetProcAddress.restype = c_void_p
proc = windll.kernel32.GetProcAddress(advapi32._handle,
b"CloseEventLog")
self.assertTrue(proc)
# This is the real test: call the function via 'call_function'
self.assertEqual(0, call_function(proc, (None,)))

@unittest.skipUnless(os.name == "nt",
'test specific to Windows')
def test_load_hasattr(self):
# bpo-34816: shouldn't raise OSError
self.assertFalse(hasattr(windll, 'test'))

@unittest.skipUnless(os.name == "nt",
'test specific to Windows')
def test_load_dll_with_flags(self):
_sqlite3 = import_helper.import_module("_sqlite3")
src = _sqlite3.__file__
if src.lower().endswith("_d.pyd"):
ext = "_d.dll"
else:
ext = ".dll"

with os_helper.temp_dir() as tmp:
# We copy two files and load _sqlite3.dll (formerly .pyd),
# which has a dependency on sqlite3.dll. Then we test
# loading it in subprocesses to avoid it starting in memory
# for each test.
target = os.path.join(tmp, "_sqlite3.dll")
shutil.copy(src, target)
shutil.copy(os.path.join(os.path.dirname(src), "sqlite3" + ext),
os.path.join(tmp, "sqlite3" + ext))

def should_pass(command):
with self.subTest(command):
subprocess.check_output(
[sys.executable, "-c",
"from ctypes import *; import nt;" + command],
cwd=tmp
)

def should_fail(command):
with self.subTest(command):
with self.assertRaises(subprocess.CalledProcessError):
subprocess.check_output(
[sys.executable, "-c",
"from ctypes import *; import nt;" + command],
cwd=tmp, stderr=subprocess.STDOUT,
)

# Default load should not find this in CWD
should_fail("WinDLL('_sqlite3.dll')")

# Relative path (but not just filename) should succeed
should_pass("WinDLL('./_sqlite3.dll')")

# Insecure load flags should succeed
# Clear the DLL directory to avoid safe search settings propagating
should_pass("windll.kernel32.SetDllDirectoryW(None); WinDLL('_sqlite3.dll', winmode=0)")

# Full path load without DLL_LOAD_DIR shouldn't find dependency
should_fail("WinDLL(nt._getfullpathname('_sqlite3.dll'), " +
"winmode=nt._LOAD_LIBRARY_SEARCH_SYSTEM32)")

# Full path load with DLL_LOAD_DIR should succeed
should_pass("WinDLL(nt._getfullpathname('_sqlite3.dll'), " +
"winmode=nt._LOAD_LIBRARY_SEARCH_SYSTEM32|" +
"nt._LOAD_LIBRARY_SEARCH_DLL_LOAD_DIR)")

# User-specified directory should succeed
should_pass("import os; p = os.add_dll_directory(os.getcwd());" +
"WinDLL('_sqlite3.dll'); p.close()")



if __name__ == "__main__":
unittest.main()
3 changes: 3 additions & 0 deletions 3 Misc/NEWS.d/next/Windows/2021-04-08-00-36-37.bpo-34816.4Xe0id.rst
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``hasattr(ctypes.windll, 'nonexistant')`` now returns ``False`` instead of raising :exc:`OSError`.


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