Re: Strings with discriminated records

[NiGHTS <nights@unku.us>]

On Sunday, May 27, 2018 at 2:07:37 PM UTC-4, Simon Wright wrote:
> 
> > I've expanded my example to include a strange run-time crash I am getting.
> >
> > Type Message (Length : Positive) is new Ada.Finalization.Controlled with record
> >     Text  :  String (1 .. Length);
> >     Cstr  :  Interfaces.C.Strings.chars_ptr;
> > end record;
> >        
> > function Create (Value : String) return Message is
> > begin
> >     return (
> >         Ada.Finalization.Controlled with Length => Value'Length, 
> >         Text => Value, 
> >         Cstr => Interfaces.C.Strings.New_String (Value) 
> >     );
> > end Create; 
> >
> > procedure Finalize (
> >     M : in out Message
> > ) is
> > begin
> >     Interfaces.C.Strings.Free ( M.Cstr ); -- Crashes here
> > end;
> >
> > declare
> >     M : Message := Create ("Hello World");
> > begin
> >     null;
> > end; 
> >
> > Why does my program crash on Finalization?
> 
> Maybe Finalize is getting called twice? You should set M.Cstr to
> Null_Ptr after freeing it.

It doesn't work. On each automatic call of Finalize, the object data is reset. Its very strange.