[Cython] Windows Debug build improvement

[Robert Bradshaw]

Who sets _DEBUG? Wouldn't manually undeffing _DEBUG be just as easy as
manually setting __PYX_WIN_DEBUG? Disclaimer: I've never developed
Python on Windows, but it seems that Nikita's solution is simpler.

On Thu, Jul 25, 2013 at 12:11 PM, WL <tds333 at gmail.com> wrote:
> On 25.07.2013 18:01, Robert Bradshaw wrote:
>>
>> On Thu, Jul 18, 2013 at 6:24 AM, Wolfgang <tds333 at gmail.com> wrote:
>>>
>>> Hi,
>>>
>>> I tried to submit a improvement for the Windows build but the tracker is
>>> not
>>> accessible without a login.
>>
>> This is to prevent spam.
>>
>>> On Windows if someone does a Debug build of an extension the flag _DEBUG
>>> is
>>> set and so the Python Interpreter sets Py_DEBUG and for all extension
>>> modules
>>> "_d" is appended to load the debug version of a module.
>>> This is not really practical because then all modules and the Python
>>> Interpreter must be build in Debug mode. For some modules this is even
>>> not
>>> possible for Windows. :-(
>>>
>>> To do a debug build for a Cython generated extension with a normal Python
>>> Interpreter (none Debug) I have to patch the pyconfig.h file and undef
>>> _DEBUG
>>> or I must patch the generated c file from Cython to undef _DEBUG before
>>> pyconfig.h or Python.h is included. (and enable it afterwards)
>>>
>>> Is it possible to add a flag to Cython to generate code that does this ?
>>>
>>> Something like described in Boost.Python:
>>>
>>> http://hepunx.rl.ac.uk/BFROOT/dist/releases/26.0.0/boost/libs/python/doc/building.html
>>>
>>> It is enough to have a new Preprocessor Flag, if set, then surround the
>>> Python.h inclusion with a disabled _DEBUG.
>>>
>>> My workarround is to disable it before pyconfig.h (Python.h) include:
>>>
>>> #ifdef _DEBUG
>>> #undef _DEBUG
>>> #define _RESTORE
>>> #endif
>>>
>>> and enable it afterwards
>>>
>>> #ifdef _RESTORE
>>> #define _DEBUG
>>> #undef _RESTORE
>>> #endif
>>
>> Seems like a fairly global change. At the very least it should be
>> guarded with an #if [windows/msvc/?], and _RESTORE probably named
>> __PYX_RESTORE_DEBUG or something less likely to clash. But it'd be
>> really helpful for someone who uses and knows windows well to comment
>> on the possible implications of this, as I don't even have a way to
>> try it out.
>
>
> Yes it should be guarded with special naming and only enabled if a new
> special option is set.
> If this new flag is not set everything is as now. A check for Windows is not
> needed, but don't bother.
>
> Something like:
>
> #ifdef __PYX_WIN_DEBUG
> #  ifdef _DEBUG
> #    undef _DEBUG
> #    define __PYX_DEBUG_RESTORE
> #  endif
> #endif
>
> ...
>
> Or test at code generation time for the flag __PYX_WIN_DEBUG and only then
> generate this surrounding code.
>
>
>
> Regards,
>
> Wolfgang
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