mORMot Open Source

syagrius

Member

Registered: 2013-02-27

Posts: 13

Possible memory leak with RecordLoadJSON using enhanced RTTI

Hi there!

I'm new to this forum.
And mOMRot is the first animal I try to tame.

I read SAD and took a look at “25 - JSON Performance” sample.

I try to unmarshalling a JSON string using RecordLoadJSON.

The JSON looks like this:

{	
	"name": "Book the First",
	"author": {
		"first_name": "Bob",
		"last_name": "White"
	}
}

I use Delphi 2010 so mORMot will automatically use enhanced RTTI information (using a TJSONCustomParserFromRTTI automatically).

This is great and everything is OK.
But FastMM4 report a memory leak.

My code to reproduce:

type
  TBookRecord = packed record
    name: string;
    author: record
      first_name:string;
      last_name:string;
    end;
  end;
var
  B:  TBookRecord;
  Json:  RawUTF8;
begin
  ReportMemoryLeaksOnShutdown:=true;
  Json :='{ "name": "Book the First", "author": { "first_name": "Bob", "last_name": "White" } }';
  RecordLoadJSON(B,@Json[1],TypeInfo(TBookRecord));
end;

Maybe I'm wrong or I forget to release something.
But I think an instance of TJSONCustomParserFromRTTI is not released.

For instance in SynCommons.pas, in function TJSONCustomParsers.TryToGetFromRTTI()

Reg.RecordCustomParser := TJSONCustomParserFromRTTI.Create(Reg.RecordTypeInfo,RegRoot);

Did I miss anything?

ab

Administrator

From: France

Registered: 2010-06-21

Posts: 14,659

Website

Re: Possible memory leak with RecordLoadJSON using enhanced RTTI

ReportMemoryLeaksOnShutdown should be set sooner in the .DPR file I suppose.

We tried to reproduce your issue, and no memory leak was reported here.
See http://synopse.info/fossil/info/886b68519349eee1e

syagrius

Member

Registered: 2013-02-27

Posts: 13

Re: Possible memory leak with RecordLoadJSON using enhanced RTTI

Thank you very much for the speed and clarity of your reply.
I updated my mORMot (also thank you about the ingenious idea of using git now).

I noticed that TestSQL3 is working without any memory leak.

But I still have a leak after moving ReportMemoryLeaksOnShutdown sooner.
I also tried Eurekalog with the same report.

There is probably something wrong in my code.
I will conduct an extensive search about my project.

ab

Administrator

From: France

Registered: 2010-06-21

Posts: 14,659

Website

Re: Possible memory leak with RecordLoadJSON using enhanced RTTI

Your code sounds correct.
Perhaps there is something wrong with the framework by we were not able to reproduce it.

syagrius

Member

Registered: 2013-02-27

Posts: 13

Re: Possible memory leak with RecordLoadJSON using enhanced RTTI

I think your can reproduce my issue.

1 - open TestSQL3.dpr
2 - comment the call to SQLite3ConsoleTests()
3 - and add my code snippet
For instance

  // SQLite3ConsoleTests;
  Json :='{ "name": "Book the First", "author": { "first_name": "Bob", "last_name": "White" } }';
  RecordLoadJSON(B,@Json[1],TypeInfo(TBookRecord));

4 - Run, You got a memory leak
5 - Reactivate the call to SQLite3ConsoleTests()
6 - Run, No memory leak!

I have been noticing another thing.
I have no leak after a simple call to RecordSaveJSON(), but only if TypeInfo points to a record without nested record

  // SQLite3ConsoleTests;   
  RecordSaveJSON(g,TypeInfo(TGUID)); // Calling RecordSaveJSON() *BEFORE* RecordLoadJSON() will remove the leak
  Json :='{ "name": "Book the First", "author": { "first_name": "Bob", "last_name": "White" } }';
  RecordLoadJSON(B,@Json[1],TypeInfo(TBookRecord));

The code above is working.

  // SQLite3ConsoleTests;   
  RecordSaveJSON(B,TypeInfo(TRecordWithNestedRecord)); // No effect
  Json :='{ "name": "Book the First", "author": { "first_name": "Bob", "last_name": "White" } }';
  RecordLoadJSON(B,@Json[1],TypeInfo(TBookRecord));

Memory leak still remain.

Last edited by syagrius (2014-07-07 07:20:05)

syagrius

Member

Registered: 2013-02-27

Posts: 13

Re: Possible memory leak with RecordLoadJSON using enhanced RTTI

I wrote a simple DPR to reproduce the memory report.
Tested under different computers with same result.

jsonleak.dpr

program jsonleak;

{$APPTYPE CONSOLE}

uses
  FastMM4,
  SynCommons;

type
  TBookRecord = packed record
    Name: string;
    author: record
      first_name:string;
      last_name:string;
    end;
  end;

var
  Json:  RawUTF8;
  B:  TBookRecord;

begin
  ReportMemoryLeaksOnShutdown:=True;

  Json :='{ "name": "How to tame a mormot", "author": { "first_name": "Bob", "last_name": "White" } }';
  RecordLoadJSON(B,@Json[1],TypeInfo(TBookRecord));
end.

ab

Administrator

From: France

Registered: 2010-06-21

Posts: 14,659

Website

Re: Possible memory leak with RecordLoadJSON using enhanced RTTI

It should be fixed now.
See http://synopse.info/fossil/info/187058910fc95b0b

Thanks for the report, and investigation.
Sorry for the delay.

syagrius

Member

Registered: 2013-02-27

Posts: 13

Re: Possible memory leak with RecordLoadJSON using enhanced RTTI

Everything is working now.
About the delay it was perfect.

Thank you!

Last edited by syagrius (2014-08-03 13:35:47)