RE: [ROOT] Problem in TStreamerInfo for old class version

From: Ruben Shahoyan (Ruben.Shahoyan@cern.ch)
Date: Wed Aug 04 2004 - 23:38:41 MEST 

Hi Philippe,
thank you, I understood the idea of the bootstrap. As for the missing initialization,
I simply forgot to put it in the curtailed version of classes I sent you...
 
Best regards,
    Ruben

	-----Original Message----- 
	From: Philippe Canal [mailto:pcanal@fnal.gov] 
	Sent: Wed 8/4/2004 9:06 PM 
	To: Ruben Shahoyan 
	Cc: roottalk (ROOT Talk mailing list) 
	Subject: RE: [ROOT] Problem in TStreamerInfo for old class version
	
	

	Hi Ruben,
	
	The crash itself in your example was due to the missing initialization in
	the class NaVertex and NaDigit1D (the default constructor needs to set
	the pointer to 0).
	
	The real problem (unable to read the objects of type NaDigit1D in your
	old files) was due to the fact that (for a reason I do not know) the
	TStreamerInfo for the version number 2 of NaDigit1D is not saved in the
	file even-though some object of that version are saved.
	
	To fix the problem I create a file that contain just the TStreamerInfo
	needed and loaded this file before reading the real file.
	
	Using the file bootstrap.C (listed below) I did (with your tar file):
	
	        $ root -q -b -l bootstrap.C+
	        $ root
	        root [0] f = new TFile("bootstrap.root");
	        root [1] .x readTree.C
	
	I.e. once bootstrap.root is generated, just load it in any ROOT
	session that needs to read the old file.
	
	Also I you have write access to the file, you can fix it by
	just doing
	        root [] .L bootstrap.C+
	        root [] f = TFile::Open("mybadfile.root","UPDATE");
	        root [] fix(f);
	
	Cheers,
	Philippe.
	
	#include "TObject.h"
	#include "TROOT.h"
	#include "TClass.h"
	#include "TStreamerInfo.h"
	#include "TFile.h"
	
	class TArrayI;
	class NaDigit1D : public TObject {
	  // This is the actually member layout of the NaDigit1D version 2
	 public:
	   NaDigit1D() : fTracks(0) {};
	 protected:
	  Int_t fI;             // Value of the digit
	  Int_t fCluster;       // Number of the Cluster to which it is attached
	  TArrayI* fTracks;     // Optional array of references on track
	  //
	  ClassDef(NaDigit1D,2) // Base class for 1Dim digits
	};
	
	
	void bootstrap() {
	   TFile * f = new TFile("bootstrap.root","RECREATE");
	   gROOT->GetClass("NaDigit1D")->GetStreamerInfo()->TagFile(f);
	   f->Write();
	   delete f;
	}
	
	void fix(TFile* f) {
	   gROOT->GetClass("NaDigit1D")->GetStreamerInfo()->TagFile(f);
	   f->Write();
	}
	
	-----Original Message-----
	From: Ruben Shahoyan [mailto:shahoian@mail.cern.ch]
	Sent: Monday, July 05, 2004 2:16 AM
	To: Philippe Canal
	Cc: roottalk@cern.ch
	Subject: RE: [ROOT] Problem in TStreamerInfo for old class version
	
	
	Sorry, I forgot to attach the files...
	Regards,
	        Ruben
	
	--
	
	On Sat, 3 Jul 2004, Ruben Shahoyan wrote:
	
	> Hi Philippe,
	> thank you. I remember the fix you did for the case when the base
	> class of the object written in non-split mode has changed. So, now
	> I am using the root_v4_00_6a. I still can read my old tree in the
	> root v_3.05, after I go back to old base class, but it crashes extactly
	> in the v4_00_6a, which became the official version of na60..
	>
	> In the attached package you can find the code necessary to reproduce the
	> problem: just run "crelib" to create the library and execute the
	> readTree.C macro.
	> Unfortunately, the smallest data file I have is ~3MB, I put a copy of it
	> on
	> /afs/cern.ch/user/s/shahoian/public/genesis_venus_noPileUp_pt7Pos_acmPos836.root
	> and
	> http://na60.cern.ch/www/Members/shahoian/genesis_venus_noPileUp_pt7Pos_acmPos836.root
	>
	> Best regards,
	>       Ruben
	>
	>

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