[ROOT] Problem with TTree and Histograms

From: Shawn Kwang (skwang@wam.umd.edu)
Date: Mon Apr 30 2001 - 17:47:16 MEST


I am having a problems with CINT and ROOT.

I have a function which declares a number of histograms (TH1F's).  In the
previous version of ROOT the code worked fine, but since we have upgraded,
something broke.  Specifically, there seems to be a problem with the TTree
variable (fChain is the variable name) and the Histogram declarations.

I added lines like this to my function to "debug" the value of fChain.

cout << "This is (1) " << fChain << endl;

Here is some code where I think things are breaking:

=====================================================

  cout << "This is (5) " << fChain << endl;

  //Declare Histograms

  Delta_R = new TH1F("Matched_Delta_R","Delta R of matched generated 
electrons", nbins1,0,7.5);

...

  cout << "This is (6) " << fChain << endl;

=====================================================

Here is the corresponding output when I run this code:

=====================================================

This is (1) 0x8829380
This is (2) 0x8829380
This is (3) 0x8829380
This is (4) 0x8829380
This is (5) 0x8829380

Error: No symbol fChain in current scope
FILE:/home/skwang/Proj4/Pmcsana1.C LINE:84

This is (6) 0

Error: No symbol fChain in current scope
FILE:/home/skwang/Proj4/Pmcsana1.C LINE:90

Error: Failed to evaluate
fChain->GetEntry(jentry) FILE:/home/skwang/Proj4/Pmcsana1.C LINE:90
Possible candidates are...
filename       line:size busy function type and name

======================================================

As you can see the variable fChain is fine for the first 5 instances, but
as soon as I declare my histograms the variable "dies."

Line 84 is: 
cout << "This is (6) " << fChain << endl;

Consequently, in line 90 when I need to use the variable fChain, my
program fails.

Line 90 is:
nb = fChain->GetEntry(jentry);

If I remove all my histogram declarations from my function the program
runs fine.

I am using ROOT version2.26/00 on a Linux (FermiLab) machine at the
University of Maryland.

Thanks in advance,
Shawn Kwang



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