Segmentation violation with graph

Newbie
1

ROOT Version: 6.22
Platform: Linux
Compiler: Not Provided

Hey all,

I’m currently running a program that has two histograms, one of which I draw a fit graph on. The first time I run it, it works fine, but if I try to load the macro again I get a segmentation violation error. When I quit root, I further get an error saying “double free or corruption (!prev)”. This only happens when I add the fit graph; without it, the code runs fine. Here’s the code in charge of graphing:

//create canvas
	auto c = new TCanvas("Z Boson Data", "Z Boson Data", 1200, 600);
	c->Divide(1, 2);

	//graph mass histogram and fit Breit-Wigner to it
	c->cd(1);
	TF1 *func = new TF1("mybw",mybw,mass_bound_low, mass_bound_high, 3);
	func->SetParameter(1, resonance_width); //get gamma/resonance width for parameter 1
	func->SetParameter(2, mass_hist->GetMean()); //get M/Z mass for parameter 2
	auto mass_fit = mass_hist->Fit("mybw", "QR");
	//mass_fit->DrawClone("Same");
	mass_hist->DrawClone("Same");

	//graph momentum histogram
	c->cd(2);
	p_hist->DrawClone("Same");

I’m not double-freeing any of these graphs with a delete statement, so I don’t know why I would be getting such an error.

Any help would be appreciated!

2

Why DrawClone and not simply Draw ?

3

I tried with this code:

// t.cxx
double mybw(double *px, double p[3]) {
  double x = *px;
  return x + p[0] + x*p[1] + x*x*p[2];
}

void t() {
  auto mass_hist = new TH1F("mass_hist", "mass_hist", 10, 0., 1.);
  mass_hist->Fill(0.21, 20);
  auto c = new TCanvas("Z Boson Data", "Z Boson Data", 1200, 600);
  c->Divide(1, 2);

  //graph mass histogram and fit Breit-Wigner to it
  c->cd(1);
  TF1 *func = new TF1("mybw",mybw,0.1, 1., 3);
  auto mass_fit = mass_hist->Fit("mybw", "QR");
  mass_hist->DrawClone("Same");

  //graph momentum histogram
  c->cd(2);
  auto p_hist = new TH1F("p_hist", "p_hist", 10, 0., 1.);
  p_hist->DrawClone("Same");
}

$ root
root [0] .x t.cxx
root [1] .x t.cxx
root.exe: /home/axel/build/root/master/src/interpreter/cling/lib/Interpreter/Interpreter.cpp:1519: void cling::Interpreter::unload(cling::Transaction&): Assertion `!T.getTopmostParent()->getNext() && "Can not revert previous transactions"' failed.

So there’s indeed a problem. Is this comparable to what you run in reality?

4

The code is comparable, but the error message is not. My error message tells me that there was a segmentation violation, that root crashed, and gives me a “stack trace of all threads.”

5

We will need code that reproduces this issue. Could you share that with us?

6

I’m using DrawClone because I’ve had problems with the graph where if I don’t use DrawClone, then the p_hist histogram simply won’t display. This is also something that wasn’t a problem before I used the fit graph.

7

As @Axel requested, can you post the code reproducing your problem ?

8

Sorry for taking so long to respond, here’s my code!
zboson_pt.C (6.3 KB)