[ROOT] Problem writing TObjArray to a file using single key

From: Marco van Leeuwen (mvl@nikhef.nl)
Date: Wed Nov 21 2001 - 14:53:12 MET 

Hi rooters,

I just started using root v3.02 instead of v2.25, and I found that some
of my macros no longer work. I traced it down to some mysterious
behaviour when writing a TObjArray to a file, using a single key. It
turns out that there is a big difference between writing a dynamically
allocated array vs. a 'statically allocated' one. I attached two macros
to illustrate the problem. First execute write_arr.C to make a file with
two arrays, one dynamically allocated, the other one statically. Using
read_arr.C to read them back in gives a surprising result: one of the
two arrays is empty (the statically aloocated array).

Did I do something wrong? Or is there something inconsistent in ROOT or
CINT ?

Best regards,

Marco van Leeuwen.

{{
  gROOT->Reset();
  TFile fout("temp.root","RECREATE");

  TObjArray obj_arr(3);
  TObjArray *obj_arr_p=new TObjArray(3);
  for (Int_t i=0; i<3;i++) {
    obj_arr[i]=new TGraph(2);
    obj_arr_p->Add(new TGraph(2));
  }
  cout << "Dump of obj_arr" << endl;
  obj_arr.Print();
  cout << endl << "Dump of obj_arr_p" << endl;
  obj_arr_p->Print();
  obj_arr.Write("obj_arr",1);
  obj_arr_p->Write("obj_arr_p",1);
  fout.Close();
}}


{{
  gROOT->Reset();
  TFile fin("temp.root");
  TObjArray *obj_arr_p1=(TObjArray*) fin.Get("obj_arr");
  TObjArray *obj_arr_p2=(TObjArray*) fin.Get("obj_arr_p");
  cout << "Dump of obj_arr" << endl;
  obj_arr_p1->Print();
  cout << endl << "Dump of obj_arr_p" << endl;
  obj_arr_p2->Print();
}}

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