[IronPython] IronPython 2.6.1 RC1, ctypes, and c_int.value

Curt Hagenlocher curt at hagenlocher.org
Thu Feb 11 07:49:49 PST 2010


Wow, that's awful.

I imagine that you would need to use VirtualProtect to make that page
writeable in order for this to work. I can't see how modifying IronPython's
ctypes to make this possible would be a good idea -- the vast majority of
uses for ctypes don't involve writing into arbitrary DLL code pages, and
it's an extremely useful protection against stray writes.
On Thu, Feb 11, 2010 at 7:39 AM, Lepisto, Stephen P <
stephen.p.lepisto at intel.com> wrote:

>  Thank you for your efforts with IronPython 2.6.1.  I am looking forward
> to the final product.
>
>
>
> I was testing 2.6.1 RC1 to see if an issue I was having with v2.6.0 was
> fixed and I ran into an interesting problem with pyReadLine (v1.13), which I
> had installed under CPython v2.6.4.  A python-based program I am testing
> requires the readline module but I am getting an odd  error when readline is
> loaded.  The error is “SystemError: Attempted to read or write protected
> memory. This is often an indication that other memory is corrupt.”
>
>
>
> I created a simple test case that shows the problem in action.  This test
> case runs fine under CPython v2.6.4 but fails under IronPython v2.6.1 RC1.
> Please ignore the fact that it is really weird-looking code and not
> something that would normally be used.  The test case demonstrates the
> problem in as few lines as possible while exercising the same steps that
> readline uses (see the install_readline() function in readline’s
> Console.py).
>
>
>
> import ctypes
>
> msvcrt = ctypes.cdll.LoadLibrary("msvcrt")
>
> systemfn = ctypes.c_int.from_address(ctypes.addressof(msvcrt.system))
>
> systemfn.value =
> ctypes.c_int.from_address(ctypes.addressof(msvcrt.system)).value
>
>
>
> The last line triggers the error: “SystemError: Attempted to read or write
> protected memory. This is often an indication that other memory is corrupt.”
>
>
>
> Apparently readline overwrites a function pointer
> (“PyOS_ReadlineFunctionPointer”) inside the DLL that implements the sys
> module so that the line input functionality passes through the python
> readline module.  Since readline uses the sys.dllhandle to get access to the
> DLL and in IronPython v2.6.1 RC1 the sys.dllhandle is 0, I’m thinking the
> pyReadline package won’t work on IronPython even if the above error is
> fixed.
>
>
>
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>
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