[pywin32-bugs] [ pywin32-Bugs-1944375 ] PyRegEnumValue fails on i18n systems

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Bugs item #1944375, was opened at 2008-04-16 21:11
Message generated for change (Comment added) made by neverjade
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Category: win32
Group: None
Status: Open
Resolution: Rejected
Priority: 5
Private: No
Submitted By: Christopher Nelson (neverjade)
Assigned to: Nobody/Anonymous (nobody)
Summary: PyRegEnumValue fails on i18n systems

Initial Comment:
If you try to enumerate the contents of the registry key:

"SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Control Panel\\Cursors\\Schemes"

pywin32 will fail with a (234, "PyRegEnumValue", ""), which means that RegEnumValue returned with ERROR_MORE_DATA.

The method pywin32 currently uses to detect the size of the value name buffer does not work properly on Windows  2003 X64 Japanese.  

To fix this bug you must make the code look like the follwing:

// @pymethod (string,object,type)|win32api|RegEnumValue|Enumerates values of the specified open registry key. The function retrieves the name of one subkey each time it is called.

static PyObject *

PyRegEnumValue( PyObject *self, PyObject *args )

{

	// This value is taken from MSDN docs.

	const DWORD maxValueNameSize=16384;



	HKEY hKey;

	PyObject *obKey;

	int index;

	long rc;

	TCHAR retValueBuf[maxValueNameSize];

	BYTE *retDataBuf;

	DWORD retValueSize = maxValueNameSize;

	DWORD retDataSize=0;

	DWORD typ;

	

	// @pyparm <o PyHKEY>/int|key||An already open key, or any one of the following win32con constants:<nl>HKEY_CLASSES_ROOT<nl>HKEY_CURRENT_USER<nl>HKEY_LOCAL_MACHINE<nl>HKEY_USERS

	// @pyparm int|index||The index of the key to retrieve.



	if (!PyArg_ParseTuple(args, "Oi:PyRegEnumValue", &obKey, &index))

		return NULL;

	if (!PyWinObject_AsHKEY(obKey, &hKey))

		return NULL;

	

	// @pyseeapi PyRegEnumValue

	PyW32_BEGIN_ALLOW_THREADS

	rc=RegEnumValue(hKey, index, retValueBuf, &retValueSize, NULL, &typ, NULL, &retDataSize);

	PyW32_END_ALLOW_THREADS

		

	// Reset because the call above messed it up.

	retValueSize=maxValueNameSize;

	// Don't need to increment because the size returned from RegEnumValue includes any needed terminators.

	retDataBuf= (BYTE * )alloca(retDataSize);

	if ((retDataBuf==NULL)){

		PyErr_NoMemory();

		return NULL;

		}

	

	rc=RegEnumValue(hKey, index, retValueBuf, &retValueSize, NULL, &typ, retDataBuf, &retDataSize);	 



	if (rc!=ERROR_SUCCESS)

	{		

		return ReturnAPIError("PyRegEnumValue", rc);

	}



	PyObject *obData=PyWinObject_FromRegistryValue(retDataBuf, retDataSize, typ);

	if (obData==NULL)

	{

		return NULL;

	}

	PyObject *retVal = Py_BuildValue("NOi", PyWinObject_FromTCHAR(retValueBuf), obData, typ);

	

	Py_DECREF(obData);

	

	return retVal;

	// @comm This function is typically called repeatedly, until an exception is raised, indicating no more values.

}

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>Comment By: Christopher Nelson (neverjade)
Date: 2008-05-14 13:09

Message:
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user_id=13396
Originator: YES

File Added: test_pywin32_reg.py

----------------------------------------------------------------------

Comment By: Christopher Nelson (neverjade)
Date: 2008-05-14 13:04

Message:
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File Added: test_winreg.py

----------------------------------------------------------------------

Comment By: Christopher Nelson (neverjade)
Date: 2008-05-14 13:03

Message:
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Originator: YES

Mark, please read the bug description. This happens on i18n systems.  For
example, Windows 2003 x64 localized in Japanese or Korean.  I am sorry that
you haven't had any bug reports on this, but I can guarantee you that if
you run that code on a w2k3 Japanese or Korean localized system, you will
hit that bug.

With respect to you comment that 

// Reset because the call above messed it up.
retValueSize=maxValueNameSize;

is wrong, I would agree with you, except that I watched the original code
not work.  I spent a number of hours tracking this problem down in our
production code, and it came back to this function in pywin32. FWIW,
_winreg manifests the same problem, in the same way.

If you read the documentation for that RegEnumValue closely, you will
realize that it doesn't actually return what you think.  Also, on i18n
systems, the ascii version of this call simply doesn't work correctly. 
Partly this is due to size limitations of the API call.  In any case, the
MSDN documentation does not try to get the key's name size, it simply uses
this value.  I suspect this is because they know that the ascii version of
this call does not work properly.

I am attaching the scripts that fail below.










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Comment By: Mark Hammond (mhammond)
Date: 2008-05-05 12:59

Message:
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I had another look at this and sadly can't repro it with that key on
win2003.  Either way, the patch as it stands needs work - eg, the code and
comment:

  // Reset because the call above messed it up.
  retValueSize=maxValueNameSize;

is wrong - the whole point of the call above was to determine the size -
so the correct fix given that approach would be to remove the first call
completely.  It also seems this would fail to work for binary values with
more than 16384 bytes from working, which best I can tell does now.  So
while I don't doubt the Japanese version of 2003 fails, I'm rejecting this
as it stands still welcome more input on the best way to approach this -
eg, the smallest script that fails for you would help - I'm assuming it
would be:

  import win32api, win32con
  key=win32api.RegOpenKey(win32con.HKEY_LOCAL_MACHINE,
                         
"SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Control
Panel\\Cursors\\Schemes",
                          win32con.KEY_READ)
  print win32api.RegEnumValue(key, 0)

FWIW, Python's _winreg module still has identical code to win32api and no
open bugs on a similar issue, so no one has reported a problem there either
(but that still doesn't mean one doesn't exist :)

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Comment By: Mark Hammond (mhammond)
Date: 2008-05-04 11:07

Message:
Logged In: YES 
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Originator: NO

Could you please attach either a patch, or the complete source file with
the new function (all the indentation is lost above)

Thanks.

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