https://github.com/python/cpython/commit/1cf5abedeb97ff6ed222afd28e650b9ecc384094
commit: 1cf5abedeb97ff6ed222afd28e650b9ecc384094
branch: main
author: Steve Dower <[email protected]>
committer: encukou <[email protected]>
date: 2026-03-02T17:10:15+01:00
summary:
gh-145307: Defer loading psapi.dll until ctypes.util.dllist() is called.
(GH-145308)
files:
A Misc/NEWS.d/next/Windows/2026-02-27-10-57-20.gh-issue-145307.ueoT7j.rst
M Lib/ctypes/util.py
diff --git a/Lib/ctypes/util.py b/Lib/ctypes/util.py
index 378f12167c6842..3b21658433b2ed 100644
--- a/Lib/ctypes/util.py
+++ b/Lib/ctypes/util.py
@@ -85,15 +85,10 @@ def find_library(name):
wintypes.DWORD,
)
- _psapi = ctypes.WinDLL('psapi', use_last_error=True)
- _enum_process_modules = _psapi["EnumProcessModules"]
- _enum_process_modules.restype = wintypes.BOOL
- _enum_process_modules.argtypes = (
- wintypes.HANDLE,
- ctypes.POINTER(wintypes.HMODULE),
- wintypes.DWORD,
- wintypes.LPDWORD,
- )
+ # gh-145307: We defer loading psapi.dll until _get_module_handles is
called.
+ # Loading additional DLLs at startup for functionality that may never be
+ # used is wasteful.
+ _enum_process_modules = None
def _get_module_filename(module: wintypes.HMODULE):
name = (wintypes.WCHAR * 32767)() # UNICODE_STRING_MAX_CHARS
@@ -101,8 +96,19 @@ def _get_module_filename(module: wintypes.HMODULE):
return name.value
return None
-
def _get_module_handles():
+ global _enum_process_modules
+ if _enum_process_modules is None:
+ _psapi = ctypes.WinDLL('psapi', use_last_error=True)
+ _enum_process_modules = _psapi["EnumProcessModules"]
+ _enum_process_modules.restype = wintypes.BOOL
+ _enum_process_modules.argtypes = (
+ wintypes.HANDLE,
+ ctypes.POINTER(wintypes.HMODULE),
+ wintypes.DWORD,
+ wintypes.LPDWORD,
+ )
+
process = _get_current_process()
space_needed = wintypes.DWORD()
n = 1024
diff --git
a/Misc/NEWS.d/next/Windows/2026-02-27-10-57-20.gh-issue-145307.ueoT7j.rst
b/Misc/NEWS.d/next/Windows/2026-02-27-10-57-20.gh-issue-145307.ueoT7j.rst
new file mode 100644
index 00000000000000..6f039197962e10
--- /dev/null
+++ b/Misc/NEWS.d/next/Windows/2026-02-27-10-57-20.gh-issue-145307.ueoT7j.rst
@@ -0,0 +1,2 @@
+Defers loading of the ``psapi.dll`` module until it is used by
+:func:`ctypes.util.dllist`.
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