TTree::GetEvent Segmentation Violation

[AndrewC]

---

_ROOT Version: 6.13
_Platform: Ubuntu 16.04
_Compiler: gcc 5.4.0

---

I have a base class defined roughly as so

class myClass {
public:
    myClass(const char* filename, const char* treename){ 
        f = new TFile(filename, "read");
        T = (TTree*)f->Get(treename);
    }
    
    doSomething(){
        for(int i=0; i<T->GetEntriesFast(); i++){
            T->GetEvent(i);
             // some code
        }
    }

    TFile* f;
    TTree* T;
}

When I try to call doSomething() I get a segmentation violation

[Wile_E_Coyote]

Try with:

class myClass {
public:
  myClass(const char *filename, const char *treename) {
    f = T = 0;
    if (!(filename && filename[0])) return; // just a precaution
    if (!(treename && treename[0])) return; // just a precaution
    f = TFile:Open(filename);
    if ((!f) || f->IsZombie()) { delete f; f = 0; return; } // file error
    f->GetObject(treename, T);
    if (!T) { delete f; f = 0; return; } // no tree
  }
  
  ~myClass() {
    delete f; // automatically deletes "T", too
    // f = T = 0;
  }
  
  doSomething() {
    if (!T) return; // just a precaution
    for(Long64_t i = 0; i < T->GetEntries(); i++) {
      if (T->GetEntry(i) < 1) break; // no entry
      // some code
    }
  }
  
  TFile *f;
  TTree *T;
};

[AndrewC]

Unfortunately that didn’t work. I should apologize though, in an effort to keep the code as simple as possible I didn’t fully explain my problem. I’ve actually fixed the problem, but I’m not satisfied with the fix. Below is an outline of what I did

class myClass {
public:
    myClass(const char* filename_1, const char* filename_2, const char* treename_1, const char* treename_2){
	f1 = new TFile(filename_1, "read");
	f2 = new TFile(filename_2, "read");

	T1 = (TTree*)f1->Get(treename_1);
	T2 = (TTree*)f2->Get(treename_2);
    }

    void AnalyzeData(){
	int nEvts = T1->GetEntriesFast();
	for(int i=0; i<nEvts; i++) processEvent(i);
    }

    virtual void processEvent(int i){ return -1; }

    TFile* f1;
    TFile* f2;
    TTree* T1;
    TTree* T2;
};

class mySubclass : public myClass {
public:
    mySubclass(const char* filename_1, const char* filename_2) : myClass(filename_1,filename_2, "tree1", "tree2"){
	/* Uncommenting will cause a crash
	Object1* pO1 = &O1;
	Object2* pO2 = &O2;

	T1->SetBranchAddress("O1", &pO1);
	T2->SetBranchAddress("O2", &pO2);
	*/
    }

    void processEvent(int i){
	/////////////////////////////////////////
	// putting it here does not cause a crash
	Object1* pO1 = &O1;
	Object2* pO2 = &O2;

	T1->SetBranchAddress("O1", &pO1);
	T2->SetBranchAddress("O2", &pO2);
	/////////////////////////////////////////
	
	T1->GetEvent(i);

	int nEvts = T2->GetEntriesFast();
	for(int e=0; e<nEvts; e++){
	    T2->GetEvent(e); // crashes here
	    // some code
	}
    }

    Object1 O1;
    Object2 O2;
};

I want to set the branches of the trees in the constructor of the subclass instead of in processEvent, but that causes a segmentation violation.

As an aside, no matter where I put the code in the constructor of the subclass (i.e. with and without a crash), calling T1->Print() or T2->Print() in processEvent prints out the trees correctly.

[Wile_E_Coyote]

Try with:

class mySubclass : public myClass {
public:
  mySubclass(const char *filename_1, const char *filename_2)
    : myClass(filename_1, filename_2, "tree1", "tree2") {
    p01 = p02 = 0;
    if (T1) T1->SetBranchAddress("O1", &pO1);
    if (T2) T2->SetBranchAddress("O2", &pO2);
  }
  
  ~mySubclass() {
    if (T1) { T1->ResetBranchAddresses(); delete p01; }
    if (T2) { T2->ResetBranchAddresses(); delete p02; }
    // p01 = p02 = 0;
  }
  
  void processEvent(Long64_t i) {
    if (!(T1 && T2)) return; // just a precaution
    
    if ((T1->GetEntry(i) < 1) || (!p01)) return; // "entry" problem
    
    Long64_t nEvts = T2->GetEntries();
    for(Long64_t e = 0; e < nEvts; e++) {
      if ((T2->GetEntry(e) < 1) || (!p02)) break; // "entry" problem
      // some code
    }
  }
  
  Object1 *pO1;
  Object2 *pO2;
};