TJson.JsonToObject throws errors in a multi-thread environment

Question

When using TJson.JsonToObject in a multi-thread environment random access violations occur. I was searching a long time for the problem and I could isolate it with

Answer 1

The method TJSONUnMarshal.ObjectInstance in REST.JsonReflect.pas has a severe bug:

It calls FreeAndNil on a TRttiType instance. This should never be done because all TRtti*** instances are managed by the TRttiContext.

After I removed the FreeAndNil call I could not reproduce the access violation anymore.

Reported as: https://quality.embarcadero.com/browse/RSP-10035

P.S. I also think that https://quality.embarcadero.com/browse/RSP-9815 will affect your code.