Serializing String with eJDO leads to AV

[DoPeRaSo]

Hello,

I have an issue while serializing a String using eJDO (I'm on Berlin 10.1 Update 1):

program SmallTest;
{$APPTYPE CONSOLE}
{$R *.res}
uses
  System.SysUtils,
  DJSON,
  DJSON.Engine.Stream,
  DJSON.Engine.DOM,
  DJSON.Utils.RTTI,
  DJSON.Params,
  DJSON.Engine.JDO;
var
  s: String;
begin
  try
    writeln( 'works: ' ,        dj.From( 'A' ).ToJson );
    writeln( 'does not work: ', dj.From( 'A' ).Engine( eJDO ).ToJson );
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
  readln;
end.

Can someone reproduce this issue?

[mauriziodm]

Hi, I've reproduced the issue with your code.
I do not know exactly why this is happening.
The error is actually triggered in the TValue code ("System.RTTI" system "TValue.AsString" method) and therefore does not appear to be closely related to serialization. But I do not understand why with other engines this does not happen (I've tried them all 3).
But I'm telling you that DJSON is not designed for use on simple values such as strings, integers and similar, as for serialization / deserialization of complex objects passed as Objects or Interfaces.
It does not make much sense to use it for individual simple values.
Or can you better explain the use you intend to do?

[DoPeRaSo]

Hi,

in fact, this was just the reduction to the lowest common denominator. I have this issue with a more complex collection of items and faced this issue there.

I did not really dig deep into it, maybe it has something to do with the way JDO handles strings (interesting and fast, but maybe problematic in conjunction with RTTI and TVale.AsString as there is some pointer magic involved....)

[mauriziodm]

Hi DoPeRaSo, I've found the problem.
I've committed some changes that solves it (and other).
Update to the last release and try it.
Let me know.
Bye.

[mauriziodm]

I realized that I did not make the latest improvements in the Master branch. Accept my apologies.
Now I did, could you kindly try to download again the latest DJSON release? You will see that now works well even with the JDO engine.
However, I would like to point out that even the "eDelphiStream" (default) engine is very interesting because, although slightly slower than the other based on JDO (not so much), it occupies about 4 times less memory during processing and this can be very important. It's my favourite.