TJson.JsonToObject< T>在多线程环境中抛出错误 [英] TJson.JsonToObject<T> throws errors in a multi-thread environment

问题描述

在多线程环境中使用 TJson.JsonToObject 时，会发生随机访问冲突。我正在寻找很长时间的问题，我可以用以下代码隔离：

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 the following code

JSON类

type
   TParameter = class
   public
      FName     : string;
      FDataType : string;
      FValue    : string;
   end;

测试功能：

procedure Test();
var
   myTasks: array of ITask;
   i : integer;
   max : integer;
begin

  max := 50;
  SetLength(myTasks, max);
  for i := 0 to max  -1  do begin
     myTasks[i] := TTask.Create(procedure ()
       var
          json : string;
          p : TParameter;
       begin
          json := '{"name":"NameOfParam","dataType":"TypeOfParam","value":"ValueOfParam"}';
          p := TJson.JsonToObject<TParameter>(json);
          p.Free;
       end);
     myTasks[i].Start;
  end;

  TTask.WaitForAll(myTasks);
  ShowMessage('all done!');
end;

这只是一个基于更复杂源代码的代码片段。只要我在一个线程中使用这个代码，一切工作都没有问题。我想知道代码是否有任何错误。

It's only a code snippet based of a much more complex source. As long I use this code in a single thread everything works without a problem. I'm wondering if there is anything wrong with the code.

推荐答案

方法 TJSONUnMarshal.ObjectInstance REST.JsonReflect.pas 有一个严重的错误：

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

它调用FreeAndNil TRttiType实例。这应该永远不会，因为所有TRtti ***实例都由TRttiContext管理。

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

在我删除FreeAndNil调用后，我无法复制访问违规。

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

报告为： https：// quality .embarcadero.com / browse / RSP-10035

PS我也认为 https://quality.embarcadero.com/browse/RSP-9815 会影响您的代码。

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

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