[vtkusers] A fix for MSVC warning D9025: overriding '/W1' with '/w'

[Niels Dekker - address until 2018]

Hi again, Cory,

Please check my merge request, and please merge, if you think it's 
fine: https://gitlab.kitware.com/vtk/vtk/merge_requests/704

Kind regards, Niels

On 23 Sep 2015 6:40 PM, I wrote:
> Hi Cory,
>
> Thanks for the information. Actually, explaining why exactly those
> warnings appear might be the hardest part! It looks like the following
> is happening, for a subproject that was meant to have suppressed
> warnings:
>    1. For such a subproject, VTK replaces any compiler option
> regarding warning-levels from CMAKE_C_FLAGS and CMAKE_CXX_FLAGS by
> '/w' and '-w'.
>    2. CMake then created a Visual Studio project file ("*.vcxproj")
> that does not have any <WarningLevel> XML tag. Instead, CMake adds
> '/w' and '-w' to the <AdditionalOptions> XML tag.
>    3. Visual Studio finds out that the <WarningLevel> tag is missing,
> and so it adds warning-level 1 ('/W1') as its default warning-level.
> However, it also adds those '/w' and '-w' from <AdditionalOptions> to
> the command-line.
>    4. The C++ compiler (cl.exe) gets '/W1, as well as '/w' and '-w',
> so it complains about overriding '/W1' with '/w'.
>
> Fortunately this problem does not occur when VTK uses '/W0', instead
> of '/w' or '-w'!
>
> Kind regards, Niels
>
> Cory Quammen wrote on September 23, 2015, 16:22:
>> Niels,
>>
>> I saw that you contributed to ITK via gerrit. Contributing to VTK is
>> similar, but it uses gitlab instead of gerrit. I wouldn't bother with
>> a bug report for this issue - just explaining why the warnings appear
>> in the commit message is sufficient.
>>
>> Thanks for offering to contribute! I will watch for your patch and
>> shepherd it through the review process.
>>
>> Best,
>> Cory
>>
>> On Wed, Sep 23, 2015 at 10:16 AM, Niels Dekker wrote:
>>
>>     Hi Cory,
>>
>>     Thank you! When I have time (hopefully before next Sunday), I'll
>>     try to contribute the patch via your gitlab contribution process.
>>     Is the process similar to ITK? And do you think I should create a
>>     "ticket" or "bug report" for this little issue?
>>
>>     If I can't get it to work (or if it takes me too much time), I
>>     hope someone else can do the patch for me, next week or so...
>>
>>        Kind regards, Niels
>>
>>     PS Also thanks to Audrius for the support  :-)
>>
>>     Cory Quammen wrote on September 23, 2015, 15:54:
>>
>>         Hi Niels,
>>
>>         This does sound like a good patch. Would you mind contributing
>>         it via
>>         our gitlab contribution process? Please see [1].
>>
>>         [1]
>> https://gitlab.kitware.com/vtk/vtk/blob/master/CONTRIBUTING.md
>>
>>         Thank you,
>>         Cory
>>
>>         On Wed, Sep 23, 2015 at 9:46 AM, Niels Dekker wrote:
>>
>>              Does anyone here think it would be nice to fix these MSVC
>>         warnings?
>>
>>              Basically it's just a matter of replacing '/w' and '-w'
>>         by '/W0',
>>              in various CMake files of the VTK source tree, according
>>         to the
>>              patch/diff-file I attached last Sunday.
>>
>>
>> --
>> Cory Quammen
>> R&D Engineer
>> Kitware, Inc.