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gh-145307: Defer loading psapi.dll until ctypes.util.dllist() is called. #145308

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gh-145307: Defer loading psapi.dll until ctypes.util.dllist() is called. #145308

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gh-145307: Defer loading psapi.dll until ctypes.util.dllist() is called.
zooba Feb 27, 2026
36bc0c3
Better comment and code change
zooba Feb 27, 2026
96a71c9
Comment typo
zooba Feb 27, 2026
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26 changes: 16 additions & 10 deletions Lib/ctypes/util.py
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Original file line number Diff line number Diff line change
Expand Up @@ -85,24 +85,30 @@ 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
if _k32_get_module_file_name(module, name, len(name)):
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
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Windows/2026-02-27-10-57-20.gh-issue-145307.ueoT7j.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Defers loading of the ``psapi.dll`` module until it is used by
:func:`ctypes.util.dllist`.
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