[Python-Dev] Deprecate invalid ctypes call protection on Windows

[Steve Dower]

On 23May2017 1212, Victor Stinner wrote:
> 2017-05-22 13:17 GMT-05:00 Steve Dower <steve.dower at python.org>:
>> Once the special protection is removed, most of these cases will become
>> OSError due to the general protection against segmentation faults.
>
> It didn't know that ctypes on Windows had a special protection against
> programming errors. I'm not aware of such protection Linux. If you
> call a function with the wrong number of arguments, it's likely to
> crash or return random data.
>
> I guess that the point is to help debugging. But since Python 3.6,
> faulthandler now registers a Windows exception handler and so it able
> to dump the Python traceback on any Windows exception:
> https://docs.python.org/dev/library/faulthandler.html#faulthandler.enable
>
> So I think that it's now fine to remove the ctypes protection. Just
> advice (remind? ;-)) users to enable faulthandler: python3 -X
> faulthandler, or call faulthandler.enable(). (You might want to use a
> log file for that on Windows, depends on the use case.)

faulthandler is already recommended in the docs, and the existing SEH 
protection for access violations will remain (since that is independent 
of libffi).

I'll be honest, I have appreciated the functionality in the past, but it 
really isn't good practice and getting rid of it will be an overall 
benefit. Technically even the segfault protection isn't a great idea, 
since you really do end up in an unknown state with regards to memory 
page allocations, but it's better than crashing all the way out.

Cheers,
Steve