[Lazarus] Callback and Threads problem

[Leonardo M. Ramé]

On 2012-04-06 14:39:10 +0200, michael.vancanneyt at wisa.be wrote:
> 
> 
> On Fri, 6 Apr 2012, Leonardo M. Ramé wrote:
> 
> >I have a similar problem to this:
> >
> >http://www.lazarus.freepascal.org/index.php?topic=10571.0
> >
> >My main program launches a thread, that loads a shared library, then
> >execute a function who receives as a parameter a pointer to a callback
> >function and an instance of the caller, as this:
> >
> >procedure TMythread.execute;
> >begin
> > ...
> > // external function
> > runcode(@MyCallBack, @Self);
> > ...
> >end;
> >
> >procedure MyCallback(const Result: PAnsiChar; const ACaller: pointer);
> >cdecl;
> >var
> > lCaller: TMythread;
> >begin
> > // the parameter ACaller is used because callbacks can't be of type
> > // procedure of object.
> > lCaller := TMyThread(ACaller);
> > lCaller.TestVar := Result; // <--- Ok.
> > lCaller.ListOfThings.Add;  // <--- SIGSEGV
> 
> IMHO the problem is not in threads.
> 
> You cannot pass objects to libraries or vice versa.
> The VMTs will differ.
> 
> Michael.

But, I'm passing the object as a pointer that is received as (void *) and
returned back to the callback as a parameter, the library doesn't touch
it. Even in this case I can't pass an object?.

-- 
Leonardo M. Ramé
http://leonardorame.blogspot.com