Re: More on the crash on exit.

>
> Martin Sevior wrote:
>> On Thu, 2007-01-11 at 15:45 +1100, Martin Sevior wrote:
>>> The crash on exit occurs with current AbiWord-2.5 on linux.
>>>
>>> It occurs because UT_ScriptLibrary::~UT_ScriptLibrary is called twice.
>>>
>>> This happens because if the are any plugins AT ALL UT_ScriptLibrary is
>>> loaded as a plugin as well as being constructed via it's static
>>> instance
>>> pointer.
>>>
>>> Upon closing AbiWord, all the plugins are unloaded, which deletes the
>>> script library once. Then the application shuts downs and hence
>>> destroys
>>> the UT_ScriptLibrary again through the static instance pointer and
>>> hence
>>> the crash.
>>>
>>> I'm now trying to understand why the library gets loaded as a plugin,
>>> which is the origin of the bug. However I've been chasing this bug for
>>> several days so I my not be successful.
>>>
>>> If I hope this info will be valuable to someone else if I can;t find
>>> the
>>> cause.
>>>
>>
>> OK I fixed this by changing the access via reference to access via
>> pointer.
>>
>> UT_ScriptLibrary is constructed in the XAP_App::initialize() method and
>> UT_ScriptLibrary::instance() returns a pointer to the class.
>>
>
> Martin,
>
> I fear that this merely covers up the real problem and introduces a new
> one; the problem is not the reference, but that something is trying to
> destroy an object that it does not own -- whatever has previously been
> calling the destructor on the reference will now call it on the pointer.
> If there is any code that has stored pointer to the singleton, that
> pointer will be invalid. I think either the class should not be a
> singleton if it makes sense to have more than one instance of it, or the
> destructor should be private and invoked at most once when the whole
> application is being destroyed.
>

Hi Tomas,
         Actually it is the whole application that is destroying the class
twice.

For some reason I can't fathom, loading ANY plugin used to create another
instance of UT_ScriptLibrary. The crash happens before the the plugin
unloaded destructs the UT_ScriptLibrary, then when abi shuts down it
destructs the UT_ScriptLibrary again, causing the crash.

Doing things this prevents the plugin loader calling another instance of
the ScriptLibrary.

I don't know why this happenned other than UT_ScriptSniffer being a
derived class UT_AbiModule. This bug has been with us for a week and I
have devoted many hours to solving it.

I agree that the solution is not satifactory because I don;t understand
why the crash happenned in the first place (see above). I do know it's
fixed and valgrind is happy with this work around.

Cheers

Martin

This now works
> Tomas
>
>
Received on Thu Jan 11 11:56:52 2007