[fpc-pascal] Reproducible code: DLL calling Firebird crashes

[Mark Morgan Lloyd]

Reinier Olislagers wrote:
> Apparently my crashes in a dll that use Firebird have to do with
> initialization sections in my business layer creating a single instance
> of my db layer.
> 
> Distilled reproducible code that demonstrates problem:
> https://bitbucket.org/reiniero/fpc_laz_patch_playground/downloads/dllcrash.zip
> 
> 1. Please update your Firebird server details in dbinterface.pas to your
> situation (hostname etc)
> 2. In businesslayer.pas, $define CRASH to see the problem.
> The code in question is:
> initialization
>   DBLayer:=TDBInterface.Create;
> 
> finalization
>   DBLayer.Free;
> ... so probably initialization order plays a part?!?
> 
> How should I fix this?

What happens if you move the responsibility for initialising and closing 
the database connection to the app-level code? In other words, the app 
does something like

   writeln('Starting demo');
   writeln('TheAnswer is:');
   InitialiseBackend;
   try
     writeln(TheAnswer)
   finally
     FinaliseBackend
   end;
   writeln('Ending demo');

-- 
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]