Tips on how to avoid Nim pointer instability bugs?

[adrianv]

IMHO that's not on the same level as the original problems. You will get the 
same result on any language that has the concept of `var` parameters and you 
are working with a pointer type. The result is as expected. The problem is a 
side effect in code flow. Here the same program in pascal.
    
    
    program Hello;
    {$mode Delphi}
    {$ASSERTIONS ON}
    
    type
        TTest = record
            flag: Boolean;
        end;
        PTest = ^TTest;
    
    var test: PTest;
    
    function newTest(): PTest;
    begin
        new(Result);
        Result^.flag := false;
    end;
    
    procedure setFlag(var flag: Boolean);
    begin
      test:= newTest();
      flag := true;
    end;
    
    begin
      writeln ('Hello World');
      test:= newTest();
      setFlag(test^.flag);
      assert(test^.flag, 'how could this happen?');
    end.
    
    
    Run