[ROOT] TTree bug. No more mistery.

From: Anton (anton.fokin@smartquant.com)
Date: Thu Apr 26 2001 - 12:38:34 MEST 

Hi Rene,

the bug appears when you make the following sequence of calls:

- read first entry in a tree
- read last entry in the tree
- write something into the tree

In this case if you have more than one basket filled in the tree you
kill root.

Check the code below:

Adding these line kills the tree:

    Int_t N = TradeTree->GetEntries();
    if (N) {
      TradeTree->GetEntry(0);
      TradeTree->GetEntry(N-1);
    }

You can change TTrade to your lovely test class.

Sincerely,
Anton

write.C

{

  gROOT->Reset();

  TFile *File = new TFile("c:\\root\\data\\test.root", "UPDATE");

  TTrade *Trade = new TTrade();

  TTree *Tree = new TTree("TradeTree", "");

  TradeTree     ->Branch("Trade", "TTrade", &Trade, 4*1024, 1);

  TradeTree     ->Write();

  for(Int_t i=0;i<20000;i++) {
    Int_t N = TradeTree->GetEntries();
    if (N) {
      TradeTree->GetEntry(0);
      TradeTree->GetEntry(N-1);
    }
    Trade->Set(i,i,i,i);
    TradeTree->Fill();
  }

  Tree->AutoSave();

  delete Tree;
  delete File;
}
read.C

{

  gROOT->Reset();

  TFile *File = new TFile("c:\\root\\data\\test.root", "UPDATE");

  TTrade *Trade = new TTrade();

  TTree *Tree = (TTree*)File.Get("TradeTree");

  Tree->SetBranchAddress("Trade", &Trade);

  Tree->Print();

  Int_t N = Tree->GetEntries();

  for(Int_t i=0;i<N;i++) {
    Tree->GetEntry(i);
    Trade->Print();
  }

  Trade->Set(0,0,0,0);

  printf("Printing second time ... \n");

  for(Int_t i=0;i<10;i++) {
    Tree->GetEntry(i);
    Trade->Print();
  }

}

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