#include "TFile.h"
#include "TEfficiency.h"
#include "TF2.h"
#include "TFitResult.h"

void segfault() {
    // Open file, get TEfficiency, create TH2 which we'll fit
    TFile* f = new TFile("THtrigger2D_HT750_18.root","READ");
    TEfficiency* eff = (TEfficiency*)f->Get("Pretag");
    // Create function, set decent starting parameters
    TF2* func = new TF2("eff_func","1-[0]/10*exp([1]*y/1000)*exp([2]*x/200)",60,260,800,2600);
    func->SetParameters(5550,-5,-1);
    // Fit function to histogram, get TFitResultPtr
    // Segfaults
    TFitResultPtr r = (TFitResultPtr)eff->Fit(func,"S");
}