Segmentation violation when creating a Th1D :(

Newbie
1

Dear root experts,
please help me with this silly question I am getting crazy and none of my colleagues found the error :frowning:
I have a macro which opens a TFile, reads the Tree contained in the file (and in particular its branch “maximum” and then fills a Th1D with the data contained in the branch:

TFile file(filename_bkg, "READ");                                                                              
  TTree* tree;                                                                                                       
  file.GetObject("EventTree", tree);                                                                                 
  EventInfo event;                                                                                                   
  tree->SetBranchAddress("maximum", &event.maximum);                                                                 
  int nEntries = tree->GetEntries();                                                                                 
                                                                                                                     
  TH1D* histogram = new TH1D("maximumPulses", "Pulses I Maximum Value", nBins, minRange, maxRange);                  
  for (Long64_t i = 0; i < nEntries; ++i) {                                                                          
    tree->GetEntry(i);                                                                                               
    histogram->Fill(event.maximum);

this works and I obtain a wonderful histogram. Now, I have to open many files and create a histogram for each file so I decided to make a method:

TH1D* CreateHisto(const char* filename){

TFile file(filename, "READ");

TTree* tree;

file.GetObject("EventTree", tree);

EventInfo event;

tree->SetBranchAddress("maximum", &event.maximum);

int nEntries = tree->GetEntries();

TH1D* h1 = new TH1D("maximumPulses1", "Pulses", 100, 0, 5);

for (Long64_t i = 0; i < nEntries; ++i) {

tree->GetEntry(i);

h1->Fill(event.maximum);

}

file.Close();

return h1;

}

and call it in the main:

 TH1D* histogram = CreateHisto(filename_bkg);
  if (histogram) {
    cout<<"the histogram exists"<<endl;
    histogram->Draw();
  } else {
    std::cerr << "Error: Unable to create histogram." << std::endl;
  }

The problem is that, the program writes “the histogram exists” but when I uncomment “histogram->Draw” I got a segmentation violation :frowning: why does it happen can you find the giant stupid mistake I made?
ps. I checked that the file exists, that the tree exists, and that the data in event.maximum are properly read, I just removed those lines from the code.

_ROOT Version: v6.22.08
_Platform: Mac OS Ventura 13.6.3 (22G436)
Compiler: Not Provided

2

Try with:

TH1D* h1 = new TH1D("maximumPulses1", "Pulses", 100, 0, 5);
h1->SetDirectory(nullptr);

I.e. Add h1->SetDirectory(nullptr); after the creation of the histogram. See:

3

Thank you so much <3

1 Like