[Mono-dev] NRE when using pointers on armhf

[Zoltan Varga]

Hi,

 Mono sets up signal handlers in order to implement throwing null reference
exceptions. This means that some SIGSEGVs etc. get converted to
NullReferenceExceptions.

              Zoltan

On Thu, Mar 26, 2015 at 5:37 PM, Slide <slide.o.mix at gmail.com> wrote:

> Yes, I can tell that the pointer is unaligned, I was wondering why I would
> get a NullReferenceException for an unaligned access. I would assume that
> mono sets up some handler or something that catches unaligned exceptions?
> Maybe not?
>
> On Thu, Mar 26, 2015 at 2:23 PM Brandon Perry <bperry.volatile at gmail.com>
> wrote:
>
>> Could also cast to an IntPtr and check the Size property, which would
>> return the number of bytes in the pointer?
>>
>>
>> https://msdn.microsoft.com/en-us/library/system.intptr.size%28v=vs.110%29.aspx
>>
>> Might be misunderstanding the issue though.
>>
>> On Thu, Mar 26, 2015 at 4:20 PM, Zoltan Varga <vargaz at gmail.com> wrote:
>>
>>> Hi,
>>>
>>>   You can check whenever the pointer is aligned by converting it into an
>>> int.
>>>
>>>              Zoltan
>>>
>>> On Thu, Mar 26, 2015 at 4:53 PM, Slide <slide.o.mix at gmail.com> wrote:
>>>
>>>> That's a good point! Can you tell me where in the mono code that the
>>>> unaligned accesses are handled? I'd just like to confirm.
>>>>
>>>> Thanks!
>>>>
>>>> slide
>>>>
>>>> On Thu, Mar 26, 2015 at 1:13 PM Zoltan Varga <vargaz at gmail.com> wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>>  arm might require aligned reads, i.e. 'p' should be 4 byte aligned in
>>>>> this case.
>>>>>
>>>>>           Zoltan
>>>>>
>>>>> On Thu, Mar 26, 2015 at 3:28 PM, Slide <slide.o.mix at gmail.com> wrote:
>>>>>
>>>>>> I am trying to compile and use the ZeroC Ice remoting library for
>>>>>> armhf to run on my RaPi 2. The compilation goes fine, but when running the
>>>>>> test suite I am getting a NullReferenceException on the pointer assignment
>>>>>> in the following code:
>>>>>>
>>>>>> fixed(byte* p = &_bytes[_position])
>>>>>> {
>>>>>>     *((float*)p) = _valBytes.floatVal; // exception here
>>>>>> }
>>>>>>
>>>>>> This same code works on x86_64, so I am assuming there is something
>>>>>> that is missing in the armhf implementation.
>>>>>>
>>>>>> Is there something I can do to debug what might be missing and
>>>>>> provide a patch? I've never done work on the mono runtime itself.
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> slide
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> Mono-devel-list mailing list
>>>>>> Mono-devel-list at lists.ximian.com
>>>>>> http://lists.ximian.com/mailman/listinfo/mono-devel-list
>>>>>>
>>>>>>
>>>>>
>>>
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>>>
>>
>>
>> --
>> http://volatile-minds.blogspot.com -- blog
>> http://www.volatileminds.net -- website
>>
>
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