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Commit b6f2fc9

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bpo-25655: Improve Win DLL loading failures doc (GH-22372)
Add documentation to help diagnose CDLL dependent DLL loading errors on windows for OSError with message: "[WinError 126] The specified module could not be found" This error is otherwise difficult to diagnose.
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‎Doc/library/ctypes.rst

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@@ -1326,6 +1326,21 @@ way is to instantiate one of the following classes:
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libraries use the standard C calling convention, and are assumed to return
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:c:type:`int`.
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On Windows creating a :class:`CDLL` instance may fail even if the DLL name
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exists. When a dependent DLL of the loaded DLL is not found, a
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:exc:`OSError` error is raised with the message *"[WinError 126] The
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specified module could not be found".* This error message does not contain
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the name of the missing DLL because the Windows API does not return this
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information making this error hard to diagnose. To resolve this error and
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determine which DLL is not found, you need to find the list of dependent
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DLLs and determine which one is not found using Windows debugging and
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tracing tools.
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.. seealso::
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`Microsoft DUMPBIN tool <https://docs.microsoft.com/cpp/build/reference/dependents>`_
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-- A tool to find DLL dependents.
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.. class:: OleDLL(name, mode=DEFAULT_MODE, handle=None, use_errno=False, use_last_error=False, winmode=0)
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