Help - SEGV when using my own class inside MakeClass() loop


I have a pre-existing tree. I used MakeClass() to generate a skeleton interface (“Whodunit” here). Inside the Loop() method, I call HistHolder::fill(), where HistHolder is a separate histogram manager class I created (simplified and attached). Its fill() method basically calls m_hist->Fill() on a private histogram.

void Whodunit::Loop() { if (fChain == 0) return;

Int_t nentries = Int_t(fChain->GetEntries());
nentries = 5000; // Cut short for this test; tree has 221K entries

HistHolder* ah = new HistHolder(“z”, “wxy”, 20, 1.0, 3.0);
ah->print(); // get here

Int_t nbytes = 0, nb = 0;
for (Int_t jentry=0; jentry<nentries;jentry++) {
Int_t ientry = LoadTree(jentry);
if (ientry < 0) break;
// get here fine

  nb = fChain->GetEntry(jentry);   nbytes += nb;
  // if (Cut(ientry) < 0) continue;

  ah->fill(Run, EBeam, EvtWght, EvtWght);
  // but never here -- though I see print statements from the end
  // of HistHolder::fill() 


When I load HistHolder.cxx dierctly (".L HistHolder.cxx"), I get a SEGV before the first loop of Loop() completes. (I never get to a print statement right after ah->fill(). ) When I use ACliC (’.L HistHolder.cxx+"), everything works fine.

What am I doing wrong?

I use:

  • Version 3.05/07 27 July 2003 *
    Compiled for alphacxx6.
    CINT/ROOT C/C++ Interpreter version 5.15.94, June 30 2003

HistHolder.cxx (5.1 KB)
HistHolder.h (2.51 KB)

When you run, can you activate teh CINT trace option?
root > .T
Instead of
root > .L HistHolder.cxx
root > .L HistHolder.cxx+
Could you send you .h,.cxx file with
the Loop function?


Hi Rene,

I’ve attached the two files that result from the TTree::MakeClass(), and included a rahter long transcript from a Root session where the error occurs, with the trace turned on.

Note the error only occurs when I load with “.L HistHolder.cxx” and not when I try “.L HistHolder.cxx+” (or "++’).


tracedump.txt (90.8 KB)
Whodunit.C (1.68 KB)
Whodunit.h (31.4 KB)

Could you send your data file …/rawTrees/incllepproc.root.224


Here’s the first 1000 entries of the tree.

smaller.root (146 KB)


Thanks to your file, I have traced the problem to be in CINT.
In HistHolder::Fill, you have the following statements
if (hist != 0) hist->Fill(value, weight);
//cout << "Run " << run << " and E = " << ebeam //OK
cout << “Run " << setw(6) << run << " and E = " << ebeam
<< " doesn’t fall into any histogram!”
<< endl;

If you remove the setw(6) from the cout statement, your program will work.
I have reported the problem to Masa.


Hi Rene,

Thanks – it works now!

Does this mean I should be cautious with my use of setw() and other manipulators (until the problem is fixed)? Or is the problem deeper, and this is just a chance symptom?

Thanks again,



You must be careful with CINT with the following logic

for (i=0;i<nentries;i++) {
if (somecondition) {
//here some object created in the stack
//may be the if is never executed
someclass xx;

In your case setw creates an object in the stack, but the above remark
is more general.
We hope that masa will be able to fix these problems in a non too distant future