TTree->GetBranch("branch") segmentation violation after removing a branch

[a.bragagnolo]

Dear root expert,
In my code I need to change entries of a particular TBranch. I figured out that the easiest way was to first remove the branch, then adding a new empty branch with the same name and then fill it.
To remove a TBranch I followed the following topic:

Easy way to delete a branch in one root file?

Hi, I have a root file with trees inside. I want to delete one branch in one tree. I understand there is one way to do this is to disable this branch and copy the tree over to a new file. However, sometimes I have many trees and only need to delete one branch from one tree, so that in the meantime I have to clone other trees one by one. I am wondering if any direct way available to remove a branch a tree? Say, get the pointer of the tree and delete one branch directly and then update the file. …

using a code more or less like this:

auto *f = new TFile(fileName, "UPDATE");
auto *t = (TTree*)f->Get(treeName);
if(t->GetBranch(branchName)) 
{
    t->GetListOfBranches()->Remove(t->GetBranch(branchName));
    t->Write();
}
f->Close();

Sadly this procedure half-broken my file. Now

auto *f = new TFile(fileName, "UPDATE");
auto *t = (TTree*)f->Get(treeName);
t->GetBranch(branchName);  //<--- segmentation violation 

gives a segmentation violation if branchName (any branchName) is not present in the TTree, while should give a null pointer.

I also tried to re-add the branch

auto *f = new TFile(fileName, "UPDATE");
auto *t = (TTree*)f->Get(treeName);
TBranch *b;
float value = -1.;
b = t->Branch(name, &value, name + "/F");
for(int i=0; i<t->GetEntries(); ++i){
    t->GetEntry(i);
    bMva->Fill();
}
t->Write();
f->Close();

But I get another segmentation violation if I try to Draw this branch:

auto *f = new TFile(fileName,);
auto *t = (TTree*)f->Get(treeName);
t->Draw(branchName); //<--- segmentation violation

What I did wrong?
What can I avoid this?

Alberto

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ROOT Version: ROOT 6.12/07
Platform: Not Provided
Compiler: Not Provided

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[pcanal]

You would also need to remove the corresponding leaves from GetListOfLeaves.

[a.bragagnolo]

How can I do it?
I find it strange that this is never mentioned in any of the topic I read about the argument.

Alberto

[pcanal]

For the ‘simple’ cases, an example is at the last post of the topic you linked.