[Lazarus] Callback and Threads problem

[Mattias Gaertner]

On Fri, 6 Apr 2012 09:45:38 -0300
Leonardo M. Ramé <l.rame at griensu.com> wrote:

> 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?.

Have you checked the calling convention. E.g. 'cdecl;'? 

Mattias