Funny behaviour in loops

ROOT
1

Dear root experts,
I experienced a funny behaviour with a for loops and std::vectors.

If I write in a macro the following lines:

files.push_back(new TFile(fileNames[0]));
cout << "files[0]->GetBestBuffer() " << files[0]->GetBestBuffer() << endl;
hTemp.push_back((TH1D*)files[0]->Get(“TurnOnMuon_1MuonIso_1Jet”));
(TH1D*)files[0]->Get(“TurnOnMuon_1MuonIso_1Jet”);
hTemp[0]->Draw();

It perfectly works. But if I put exactly the same lines in a for loop:

for(int i=0; i<fileNames.size(); i++) {
files.push_back(new TFile(fileNames[0]));
cout << "files[0]->GetBestBuffer() " << files[0]->GetBestBuffer() << endl;
hTemp.push_back((TH1D*)files[0]->Get(“TurnOnMuon_1MuonIso_1Jet”));
(TH1D*)files[0]->Get(“TurnOnMuon_1MuonIso_1Jet”);
hTemp[0]->Draw();
}

It crashes at the line hTemp.push_back((TH1D*)files[0]->Get(“TurnOnMuon_1MuonIso_1Jet”));

I noticed that, without the for loop, the line:
cout << "files[0]->GetBestBuffer() " << files[0]->GetBestBuffer() << endl;

gives as result 1024, in the for loop it gives 0. I really do not understand how the presence of the loop can change the file content. Any help will be apreciated.
Thanks,
Massimiliano

2

Do you really want to open file with name fileNames[0] fileName.size() times? Or it’s better use new TFile(fileNames[i]); ???

Do you really want files[0] or it should be files[i] ?