Hi Ben,
After further investigation, I noticed that you have one more problem
in your code. The memory is allocated with:
array = new short[fArraySize]; //with fArraySize==fNwire*fNchan;
then it is accessed with:
for(Int_t i=0; i<fNwire; i++) {
for(Int_t j=0; j<fNchan; j++) {
array[i*(fNchan+1)+j] = (Short_t)(i+j);
Note that the index being used is i*(fNchan+1)+j, given
the loop the range of this index is from fNchan to fNwire*(fNchan+1)
which is way beyhond the end of the allocated memory. This will cause
all kind of problems, including but not limited to core dumps is weird
places.
Instead use:
for(Int_t i=0; i<fNwire; i++) {
for(Int_t j=0; j<fNchan; j++) {
array[i*fNchan+j] = (Short_t)(i+j);
Cheers,
Philippe.
-----Original Message-----
From: owner-roottalk@pcroot.cern.ch
[mailto:owner-roottalk@pcroot.cern.ch]On Behalf Of Ben Morgan
Sent: Friday, March 01, 2002 7:53 AM
To: roottalk@pcroot.cern.ch
Subject: [ROOT] A very strange TTree problem
Hi ROOTers,
I'm encountering a strange problem when trying to store a class
in a TTree. The problem appears to be with the 1D dynamic array data
member that I'm using. In the application program (see below), the
class (and array) can be generated and the values of the array printed to
the screen no problem within the for loop. However, when I add the lines
which generate the
TTree and TBranch, the array is generated on the first pass through the
loop, but the app then falls over on the second pass through the loop with
a segmentation violation. I've done some investigation on this and it
appears that the fault originates with the 'delete array' statement in the
SetArray() method of the class (see below). However, I cannot understand
why this causes the problem, as the code is just adapted from the Event
example in the manual. Also, I've written another class with identical
coding for dealing with dynamic arrays that works no problem. Can anyone
resolve the problem - I admit it's probably my coding.....? (I'm using
ROOT v3.01/06 on a PC running RH6.2).
Thanks,
Ben Morgan.
-Class data header-
#ifndef __data_h
#define __data_h
#include<iostream.h>
#include "TObject.h"
#include "TRandom.h"
class data : public TObject
{
private:
Int_t fNwire;
Int_t fNchan;
Int_t fArraySize;
Short_t *array; //[fArraySize]
public:
data();
virtual ~data();
void SetWC(Int_t a, Int_t b) {fNwire=a; fNchan=b; fArraySize=a*b;}
void SetArray();
void Display();
ClassDef(data,1)
};
#endif
-Class data implementation-
#include "data.h"
ClassImp(data)
data::data()
{
fNwire=0;
fNchan=0;
array=0;
}
data::~data()
{
delete [] array;
}
void data::SetArray()
{
cout<<"In SetArray"<<endl;
delete array;
cout<<"Deleted Array"<<endl;
if(!fArraySize)
{
array=0;
return;
}
array = new short[fArraySize];
cout<<"Created new array"<<endl;
for(Int_t i=0; i<fNwire; i++)
{
for(Int_t j=0; j<fNchan; j++)
{
array[i*(fNchan+1)+j] = (Short_t)(i+j);
}
}
}
void data::Display()
{
cout<<"\n";
cout<<"fArraySize = "<<fArraySize<<endl;
for (Int_t i=0; i<fNwire; i++)
{
for(Int_t j=0; j<fNchan; j++)
{
cout<<array[i*(fNchan+1)+j]<<" ";
}
cout<<endl;
}
}
-Application using data class-
#include <iostream.h>
#include <stdlib.h>
#include "TROOT.h"
#include "TFile.h"
#include "TTree.h"
#include "TBranch.h"
#include "data.h"
int main(int argc, char *argv[])
{
TFile *dfile = new TFile("datatree.root", "RECREATE");
TTree *tree = new TTree("RawData", "A Tree with data Objects");
data *d1 = new data();
TBranch *branch = tree->Branch("data_branch","data", &d1,16000,2);
for(Int_t i=0; i<10; i++)
{
d1->SetWC(8,10);
d1->SetArray();
//Falls over here on second pass through loop
d1->Display();
tree->Fill();
}
tree->Print();
dfile->Write();
dfile->Close();
delete d1;
return 0;
}
--
-------------------------------------------------------------------------------
Mr. Ben Morgan
Postgraduate Student
University of Sheffield
Department of Physics & Astronomy
Hicks Building
Hounsfield Road
Sheffield S3 7RH
-------------------------------------------------------------------------------
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