Re: [Jsbsim-devel] Release of v1.0 (with a fix suggestion to my multiple JSBSim objects issue)

[Bertrand C. <bco...@gm...>]

Hi all,

Unfortunately, Ola's patch introduced a couple of glitches that
prevent Flight Gear to run.

One of them has originally been fixed by Frédéric Bouvier in the
Flight Gear git repository. I have just transposed his patch and
renamed the variable 'delete_root' in 'StandAlone' because I assume
that a new 'Root' property manager would only be created when JSBSim
is running in stand alone mode.

The second issue crashes Flight Gear while starting because the
allocation of a new FDMctr must be done if FDMctr was initially set to
its default NULL value even if Root is not NULL. Otherwise a
segmentation fault occurs when reaching the line 149 of
src/FGFDMExec.cpp :

  IdFDM = (*FDMctr); // The main (parent) JSBSim instance is always the "zeroth"

Attached is a patch that fixes these 2 bugs.

Cheers,

Bertrand.

2010/9/27 Ola Røer Thorsen <ol...@si...>:
> Hi Jon,
>
> sorry no not yet, I've been away travelling for a week. I'll try to
> get it done within a couple of days. I made sort of a mess of the code
> while figuring it out, so I need to clean it up a bit first :-)
>
> Best regards,
> Ola
>
>
>
>
> 2010/9/25 Jon S. Berndt <jon...@co...>:
>> Ola,
>>
>> Did you send me a patch for this, yet?
>>
>> Jon
>>
>>
>>> -----Original Message-----
>>> From: Ola Røer Thorsen [mailto:ol...@si...]
>>> Sent: Tuesday, September 14, 2010 3:03 PM
>>> To: Development issues
>>> Subject: Re: [Jsbsim-devel] Release of v1.0 (with a fix suggestion to
>>> my multiple JSBSim objects issue)
>>>
>>> I've looked further into the code and found some bugs and potential
>>> problems.
>>>
>>> The first one is in FGFDMExec's destructor. It has a try/catch block,
>>> in which it checks for Root == 0, and if so, deletes the object
>>> pointed to by the static pointer "master". Root can never be zero, so
>>> this part is never executed, and the FGPropertyManager object is never
>>> deleted. Root is never zero because it's set to be the same as master,
>>> in FGFDMExec's constructor right after the line
>>> master = new FGPropertyManager();.
>>>
>>> So to try to fix this I added a member variable "bool GotMaster" being
>>> set to true if Root was NULL in FGFDMExec's constructor (thus creating
>>> the master object), and replaced the check for Root == 0 to check if
>>> this flag is true. Then master gets deleted. Also I had to add "master
>>> = NULL;" after deleting it.
>>>
>>> This actually fixes my issue. I can create a FGFDMExec object, delete
>>> it again, and create another one, and so on. :-)
>>>
>>> But then I tried to run several aircraft at the same time. This works
>>> ok until I try deleting one of them, which causes a crash. I think
>>> this is basically caused because the master pointer is static and
>>> thereby shared by all the FGFDMExec objects.
>>>
>>> So then I just removed the static master pointer completely, changed
>>> the constructor so that if Root == 0 then Root = new
>>> FGPropertyManager(), and in the destructor, just delete Root instead.
>>> Now everything works just fine! :-)
>>>
>>> So I need some input from you guys now -- I can't really see the real
>>> use for the "master" pointer at all, it's barely used by the FGFDMExec
>>> class, and it's also not declared as a public variable (neither is
>>> Root). The child FDM's (If I understand JSBSim correctly) should get
>>> the Root pointer passed to them anyway so they also don't need it. Now
>>> they actually don't - in FGFDMExec::ReadChild, the object is created
>>> without passing the Root pointer, for some reason, so right now, my
>>> fix has probably broken something somewhere. What are the child FDM's
>>> for?
>>>
>>> Best regards,
>>> Ola
>>>
>>> -----------------------------------------------------------------------
>>> -------
>>> Start uncovering the many advantages of virtual appliances
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>>> _______________________________________________
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>>> _______________________________________________
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>>> http://www.JSBSim.org
>>> _______________________________________________
>>
>>
>> ------------------------------------------------------------------------------
>> Start uncovering the many advantages of virtual appliances
>> and start using them to simplify application deployment and
>> accelerate your shift to cloud computing.
>> http://p.sf.net/sfu/novell-sfdev2dev
>> _______________________________________________
>> Jsbsim-devel mailing list
>> Jsb...@li...
>> https://lists.sourceforge.net/lists/listinfo/jsbsim-devel
>> _______________________________________________
>> The JSBSim Flight Dynamics Model project
>> http://www.JSBSim.org
>> _______________________________________________
>>
>>
>
> ------------------------------------------------------------------------------
> Start uncovering the many advantages of virtual appliances
> and start using them to simplify application deployment and
> accelerate your shift to cloud computing.
> http://p.sf.net/sfu/novell-sfdev2dev
> _______________________________________________
> Jsbsim-devel mailing list
> Jsb...@li...
> https://lists.sourceforge.net/lists/listinfo/jsbsim-devel
> _______________________________________________
> The JSBSim Flight Dynamics Model project
> http://www.JSBSim.org
> _______________________________________________
>
>