Re: Avoid global pointers in dae

[Francesco Faccio]

Carlo de Falco<address@hidden> wrote:
>On 14 Aug 2016, at 02:11, Carlo de Falco <address@hidden> wrote:
>
>>
>> On 14 Aug 2016, at 01:17, Carnë Draug <address@hidden> wrote:
>>
>>> On 13 August 2016 at 06:30, Francesco Faccio
>>> <address@hidden> wrote: 
>>>> [...]
>>>> Since I don't own copiright, I would like to know if it's ok to change the
>>>> interface of that base class. 
>>>>
>>>
>>> The ability to change the code is one of the main points behind GPL.
>>> So yes, you can change the source.
>>>
>>> Just beware that if the interface is public you should try to keep
>>> backwards compatibility.  I grepped all of the Octave Forge for DAEFunc
>>> and all of its subclasses [1] but couldn't find it being used so you
>>> should be fine.
>>>
>>> Carnë
>>>
>>> [1] http://octave.org/doxygen/4.1/d9/d83/classDAEFunc.html
>>
>> Francesco,
>>
>> As Carnë's answer shows, your question is ill posed and leads to misunderstandings:
>>
>> of course you can change the source, the GPL license grants you this right,
>> the real question would be whether that change would be accepted by Octave
>> developers in the main repository or not.
>
>To make this more clear, who holds copyright is pointless and referring to that
>in your question is distracting.
>
>The question is a technical question about the class design and functionality, not
>a legal question about licenses and copyright.
>
>> c.

Carlo, Carnë,

sorry, my question was not well posed and thank you for making this clear to me. 

I'm not still sure we can avoid global pointers wrt the design of Octave. Let me explain why:

In my dld-function I have a pointer to the octave_function provided by the user and I use it inside a  DAERHSFunc to compute residual. I use a pointer to this DAERHSFunc when I construct an object of my class.

Inside my class I have methods which allows me to interface with Sundials' types and functions. In particular, I use a lambda to pass a residual function (with fixed signature) to a function of Sundials (with fixed signature). 

The problem here is that I cannot use classes and methods of libinterp inside liboctave to compute residual, I can only put a forward declaration in my class.

My first and actual solution is to call inside my lambda a pointer (stored in the base class) to the DAERHSFunc defined in my dld-fun, so I can call methods of class octave_function and I avoid code duplication, but I need to declare the poiner to octave_function global in my dld-function.

What I was trying to do, was to store the octave_function pointer as member of my class and to pass it as a parameter when I dereference the pointer  to the DAERHSFunc  in my lambda.  But since it has incomplete type I get segmentation fault. 

I think I could avoid global pointers changing completely the constructor of my class, but then inheriting from DAE would be meaningless.

Do you have any suggestions or do you know some workaround to this?

Thank you,

Francesco