Hi!
I created a C application which calls methods from a library developed in Pascal.
I can create objects by using
void *test;
test = br_object_new ();
and access the object too, but when I try to free an object after it has been used, I get a segfault in SYSTEM_TOBJECT_$__CLEANUPINSTANCE. The code to free an object looks like to following: procedure br_object_free(obj: PObject);cdecl;
begin
if obj^ = nil then exit;
FreeAndNil(obj^);
end;
I can access all properties of obj^, as well as calling methods. I only cannot free the object.
Does someone have an idea why the application behaves like this? I use FPC 2.4.0.
Kind regards
Matthias Klumpp

Matthias Klumpp kirjoitti maanantai 13 joulukuu 2010 18:50:46:

if obj^ = nil then exit; FreeAndNil(obj^);

Shouldn't it be:

 // if obj = nil then exit;  <-- not really needed
 FreeAndNil(obj);

Juha

Yes, right. The first line was only for testing. But removing the line, of course, does not affect the behavior in any way, which means the error is still present.
Regards
Matthias

Did you notice that Juha removed the "^" after "obj" as well? How is PObject defined? Maybe you should just work with TObject directly, cause a class instance variable is already a pointer.

So:

function create_fpc_class_xy: TObject; cdecl;
begin
   Result := TClassXY.Create;
end;
procedure free_fpc_class(aObject: TObject); cdecl;
begin
   aObject.Free;
end;
In c:
void* create_fpc_class_xy();
void free_fpc_class(void* aObject);

Regards,
Sven