RE: [ROOT] Segmentation fault. Cause: Closing a TFile

From: Philippe Canal (pcanal@fnal.gov)
Date: Wed Jul 02 2003 - 18:29:18 MEST 

Hi Pierre-Luc,

When you close a file, all the objects 'Appended' to this file are deleted.
In particular, histogram and trees are automatically appended to the current
directory.  Hence, 'myfile->Close();' as the side-effect of deleting ctbuf.

You might want to (re)read the chapter on object ownership in the ROOT Users
Guide.

Note that your code is missing (at least in this copy/pasted version) and
essential
	myfile->Write();
without which the tree is not fully written/flushed to the file.

Cheers,
Philippe

-----Original Message-----
From: owner-roottalk@pcroot.cern.ch
[mailto:owner-roottalk@pcroot.cern.ch]On Behalf Of Pierre-Luc Drouin
Sent: Wednesday, July 02, 2003 11:03 AM
To: roottalk@pcroot.cern.ch
Subject: [ROOT] Segmentation fault. Cause: Closing a TFile


Hello,

I've to open a TFile, get a TTree instance from it, and copy this TTree
with some selections to a new TTree object and then to close the TFile. My
code is the following:

	    TTree *tbuf, *ctbuf;
            TDirectory* fluxdir= \\A pointer to a TDirectory in a TFile
            TDirectory *ctdir;

	    TFile *myfile=new TFile("myfile.root","READ");


          tbuf=dynamic_cast<TTree*>(myfile->Get("mytree"));

	    ctdir=fluxdir->mkdir("Event Info");
	    ctdir->cd();

	    ctbuf=tbuf->CopyTree(allcuts);

	    myfile->Close();
	    gROOT->Delete(cardbuf[i][filenameindex]);


I get a segmentation fault when I try to ctbuf->Draw() further in the
code. Since gDirectory==ctdir in the code, I don't understand how ctbuf
could depend on myfile. When I comment the last two lines in the code,
everything works fine

Thank you

Pierre-Luc Drouin

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